Standardized Preparation and Extraction Efficiency of Traditional Aqueous Kava Beverages

1. Introduction

Piper methysticum Forst. f. is a perennial shrub cultivated throughout the South Pacific for its ceremonial, medicinal and social significance. The traditional beverage, prepared from peeled root and basal stump macerated in water, has been consumed for centuries and remains central to cultural practice across Polynesia, Micronesia and Melanesia [1,2]. Its physiological effects are attributed to a group of lipophilic α-pyrones known as kavalactones, of which six — methysticin, dihydromethysticin, kavain, dihydrokavain, yangonin and desmethoxyyangonin — normally account for the great majority of the total present in root tissue and are the compounds quantified here [3–5]. Because the six vary in relative proportion between cultivars, a cultivar is conventionally described by its chemotype: the six are ranked in descending order of concentration and their identifying numbers written as a six-digit code, in which 1 denotes desmethoxyyangonin, 2 dihydrokavain, 3 yangonin, 4 kavain, 5 dihydromethysticin and 6 methysticin [6]. A code of 254631 therefore denotes a cultivar in which dihydrokavain is the most abundant kavalactone and desmethoxyyangonin the least. The code is largely characteristic of a cultivar, but absolute kavalactone content — and occasionally the rank order of closely spaced compounds — responds to growing site, plant age and the tissue sampled, so a chemotype should be read as a property of a cultivar grown under stated conditions rather than as an invariant fingerprint [7].

Kava has become increasingly globalized, with expanding consumption in Western markets through kava bars, packaged beverages and dietary supplements [8]. That expansion is now measurable in the United States: a nationally representative survey of 2,000 US adults found 10.7% reporting past-year kava use, with the home the most frequently reported setting of consumption at 59.4% of users and kava bars reported as a purchase setting by 33.7% [9], while accounts drawn from online user communities describe a correspondingly wide range of preparation practices and self-selected doses [10]. Safety scrutiny over the same period has focused on hepatic effects attributed to particular constituents and to non-aqueous preparation types [11,12], and subsequent analyses of that episode have argued that the decisive quality variables were raw-material identity and preparation type rather than kavalactone content alone [13,14]. The commercial and the safety literature therefore converge on one requirement: a preparation whose parameters are fixed and disclosed, and a beverage whose delivered dose is measured rather than inferred from the composition of the root.

Traditional preparation relies on manual maceration of ground kava material in water inside a porous straining bag, which is kneaded and wrung until the liquid takes on the opaque, sediment-laden appearance characteristic of the beverage [2,15]. The strainer is a coarse filter rather than a clarifier: it retains the fibrous marc while allowing fine particulate to pass into the cup, so the finished beverage is a suspension of root solids in water and not a clarified aqueous extract [16]. The distinction is not merely descriptive. Whole kava extracts and isolated kavalactones do not behave equivalently in biological assay [17]. That comparison is between a whole extract and purified compounds rather than between a particulate suspension and a clarified liquid; read together with the physical character of the strained beverage, however, it supports the inference — drawn here rather than reported in the cited work — that the particulate and matrix-associated material carried through the strainer is part of what the drinker actually receives. Manual preparation also introduces substantial variability arising from differences in bag porosity, kneading duration, operator strength and handling practice. Such inconsistency complicates both research reproducibility and consumer experience, particularly as commercial operators attempt to scale production.

Against this background the literature on aqueous extraction efficiency is openly contradictory. Cold-water infusions have been reported to recover as little as 5–10% of the kavalactones present in the root [18], and a traditional aqueous preparation has been estimated to carry only about 3% of the kavalactone yield obtained from the same material with acetone [19]; against this, gas-chromatographic work on Fijian yaqona reported that 81–83% of the major active constituents were transferred into the beverage [20,21]. Solvent-comparison studies consistently find aqueous extracts substantially weaker than organic extracts of the same material without resolving the size of the gap [22,23]. Part of the disagreement is definitional, since a figure for a filtered liquid and a figure for a whole beverage are not the same quantity. On the reading adopted here, the low recoveries [18,19] describe kavalactone recovered in clarified solution, while the yaqona figure [20,21] describes transfer into the strained beverage as consumed, with suspended particulate included. Neither source frames its result in those terms, so this assignment is an interpretation offered here rather than a method reported in the cited work. Part of the disagreement is nonetheless physicochemical. The only compiled water-solubility values available for the individual kavalactones — dihydrokavain 8.1, kavain 2.2, dihydromethysticin 1.5, methysticin 1.2, desmethoxyyangonin 0.5 and yangonin 0.3 mg per 100 mL at 21 °C — sum to under 14 mg per 100 mL [24], an order of magnitude below the kavalactone concentration routinely measured in a traditional preparation. Those values originate in an unpublished 1997 conference presentation [25] and no accessible primary measurement of them could be located, so they are indicative rather than authoritative; but even read loosely they imply that a recovery figure in the eighties cannot be describing dissolved material. Reconciling the two ends of the range requires a preparation in which the transfer of solids and the dissolution of kavalactones are measured separately rather than inferred from a single assay of the finished liquid.

Mechanical preparation systems have emerged as alternatives to manual kneading, yet few have been evaluated rigorously for their ability to reproduce traditional beverage characteristics, and the published work that does quantify beverage composition has generally varied solvent or tissue rather than the mechanics of the preparation itself [26]. The Alu Bottle Shaker® employs a 70 µm Alu Ball® straining vessel and fixed shaking parameters, reducing operator-dependent variability while maintaining the particle-rich suspension that defines traditional aqueous kava. By standardizing water temperature, run time, water volume and filtration threshold, the system allows extraction efficiency and chemical outcomes to be compared systematically across varieties; and because the marc is retained intact inside the straining vessel, it permits a closed mass balance in which the kavalactone delivered to the beverage is obtained by difference from the residue rather than by assay of the liquid alone.

Acidification was included as a second condition for a specific reason. Kavalactones are neutral α-pyrones with no ionizable group, so lowering the pH of the extraction water should not alter their intrinsic solubility directly; any effect must act on the plant matrix, for example through acid-assisted hydrolysis of pectic material and consequent loosening of cell-wall structure, or through changes in the swelling and dispersion behavior of starch. Concurrent work by the present authors, using a commercial blender and fresh-frozen material drawn from the same cultivars, indicated that lowered pH may improve kavalactone recovery [27], and the acidified condition was included here to test whether that effect survives in a fixed-geometry, dried-material system. The expectation was therefore modest: a matrix-mediated effect, if present at all, should be small relative to the mechanical variables.

The present study uses this standardized preparation system to evaluate extraction efficiency and kavalactone partitioning across three American varieties (Kali-ISA, Kali-Rogu and Kali-Hiwa) and one Papua New Guinea variety (“Koniak”). The specific objectives were (i) to quantify kavalactone recovery from a single extraction cycle and from a sequential re-extraction of the marc, (ii) to apportion the kavalactones delivered to the beverage between suspended particulate matter and truly dissolved compounds, and (iii) to assess the influence of pH (8 versus 5) on overall recovery and distribution. The working hypothesis, following from the solubility figures above, was that the dissolved fraction would be small and bounded by solubility rather than by process efficiency; that the great majority of the delivered kavalactone would therefore travel as suspended particulate; and that chemotype rank order would consequently be transmitted from root to beverage substantially intact, because particulate transfer is not compound-selective in the way dissolution is.

2. Materials and Methods

2.1. Reagents and Equipment

Water was reverse-osmosis-filtered tap water, which measured pH 8.0 by meter at the point of use; the reading was confirmed before each extraction. Citric acid (ACS reagent grade) was obtained from Sigma-Aldrich (St. Louis, MO, USA). The Alu Bottle Shaker® machine, 70 µm Alu Ball® straining vessels and Alu Shaker® Pro bottles were provided by Kavafied (Sarasota, FL, USA). Drying used an Avantco 1000 W commercial food dehydrator with digital temperature and timer control. pH was measured with an Apera Instruments PH20 pocket pH meter, calibrated daily against pH 4.00, 7.00 and 10.01 buffers. Residual moisture was determined with a U.S. Solid USS-HMA21 moisture analyzer. Samples were milled in a Shardor CG628B 200 W four-blade spice mill.

2.2. Plant Materials

Kava plants of the varieties Kali-ISA, Kali-Rogu and Kali-Hiwa were grown under greenhouse conditions at the American Kava Association Research Greenhouse in Sacramento, California, and harvested in September 2025. The Kali-Rogu and Kali-Hiwa plants were three years old at harvest; the Kali-ISA plant was eighteen months old. Plant age at harvest is therefore not uniform across the American varieties and is a confound on any comparison involving Kali-ISA, since kavalactone accumulation and lignification of the root both progress with age. Material was washed thoroughly, size-reduced in a commercial food processor, flash-frozen and stored at −20 °C. A 454 g frozen sub-sample was drawn from each lot and air-dried at 38 °C for 48 h to 3.0% residual moisture, verified by moisture analyzer. An additional dried sample of Papua New Guinea kava, “Superior Koniak” batch VHM-020324, was provided by Root of Happiness (Las Vegas, NV, USA) and was further dried alongside the other samples to the same 3.0% residual moisture.

2.3. Botanical Identification, Chemotype and Beverage-Grade Classification

Botanical identity and chemotype were established by two complementary methods and read together. Identity was determined by high-performance thin-layer chromatography (HPTLC) at Flora Research Laboratories, LLC (Grants Pass, OR, USA) under job identifier J25-0930-H, on dried homogenized root material drawn from the same lots used for the extractions reported here. The method followed the Piper methysticum root identity protocol of the British Herbal Pharmacopoeia [28], modified for modern HPTLC instrumentation: chloroform extraction under sonication, application to silica plates carrying an F254 fluorescence indicator, development in ethyl ether, and imaging under white light after vanillin–sulfuric acid derivatization and under UV at 366 nm. Each sample was applied in duplicate at two volumes and chromatographed on a single plate alongside two authenticated P. methysticum reference materials and a kavain reference standard. Chemotype was determined separately on the same lots from the quantitative HPLC-UV data reported in Section 2.5, by ranking the six major kavalactones in descending order of concentration, with flavokavains A, B and C quantified in the same analytical run. HPTLC therefore addresses what the material is; HPLC-UV addresses what it contains; neither was relied on alone.

All three American cultivars produced the characteristic intense band at an Rf of approximately 0.4, corresponding to the principal kavalactone zone of the reference materials, with co-migration of the kavain standard, together with the diagnostic blue-fluorescing bands at Rf 0.4–0.5 and the red-fluorescing upper band under UV 366 nm. Formal identity determinations were issued by the laboratory in signed reports for each sample. HPTLC of this kind establishes consistency with authenticated P. methysticum reference material; taken alone it does not discriminate P. methysticum from its wild progenitor P. wichmannii, whose kavalactone profile overlaps substantially, which is why the chemotype result is read alongside it. The Papua New Guinea material was obtained as a commercial dried batch and was not HPTLC identity-tested; it is described here by its trade designation, and its chemotype and flavokavain content were determined on the same basis as the others.

Read together, the two determinations place all four materials within the range of cultivated kava. The chemotypes of the starting materials were 254631 for Kali-ISA, 256431 for PNG Koniak, 423516 for Kali-Rogu and 463251 for Kali-Hiwa (Table 6). Each is a kavain- or dihydrokavain-led code of a kind documented among the cultivated varieties grown in Hawaii, Vanuatu and Papua New Guinea [2,6,7]. None matches any of the codes assigned to wild forms related to P. wichmannii in the classification framework applied to these lots — 512, 521, 251 and 215 — every one of which places desmethoxyyangonin among the three leading positions, whereas desmethoxyyangonin occupies the fifth or sixth position in all four materials examined here [33]. On the combined evidence of an authenticated P. methysticum banding pattern and a cultivated-type kavalactone rank order, the material studied is consistent with cultivated varieties and is not wild-type material.

Beverage grade and non-beverage grade are lot-release categories, not descriptions of effect, and they rest on two separate questions that are frequently conflated. The first is cultivar class. The Codex regional standard for kava products prepared as a beverage with water requires raw material of a known noble variety, confirmed by morphological characteristics, and excludes wild kava, P. wichmannii, and two-day or tudei varieties [29]; Vanuatu’s Kava Act No. 7 of 2002 draws the same fourfold distinction between noble, tudei, medicinal and wichmannii material for the purposes of trade [31]. The second question is chemistry, and specifically flavokavain content. Flavokavains A, B and C are chalcones measured alongside the kavalactones but excluded from the total kavalactone calculation, and they are the analytical markers by which non-noble material is distinguished; flavokavain B rather than flavokavain A is the compound associated in the literature with tudei profiles carrying high dihydromethysticin, dihydrokavain and flavokavain B [30,32]. The harmonized multinational kava standards (Version 1.1, November 2024) set the beverage limit at a combined flavokavain A, B and C content of not more than 0.4% w/w on a dried basis and not more than 5% of the total kavalactone content [30]. The American Kava Growers Manual adopts that 0.4% w/w limit as the release criterion for dried lots, a result above which fails release unless a buyer’s binding requirement provides otherwise [32], and Root of Happiness applies the same two figures as its own lot specification, resolving every lot it evaluates to one of exactly two outcomes: beverage grade or non-beverage grade [33].

The two questions do not answer each other, and that is the practical content of the distinction. A kavalactone chemotype ranks the six major lactones by relative abundance and carries no information about flavokavain concentration, so a textbook kavain-led ranking accompanied by flavokavains above 0.4% is non-beverage grade however favourable the chemotype appears, and conversely a low flavokavain result does not by itself make a lot a Codex noble variety [33]. Non-beverage grade therefore comprises everything above the flavokavain limit, together with tudei and wild cultivars, and such material is not sold for drinking [33]. The two limbs are assessed independently, and the cultivar limb is not settled by chemotype alone: chemotypes 254 and 256 occur in both Isa and tudei material, so within this framework chemotype 253 is treated as tudei in all cases, while 254 and 256 resolve to tudei only where total flavokavains exceed the 0.4% w/w limit and to beverage-grade Isa where they fall below it [33]. Plant material matters on the same footing as chemistry: beverage-grade product is restricted to peeled rootstock, lateral roots and basal stump tissue, and leaves, branches, upper stems, unpeeled bark, peelings, and tissue of unknown plant-part identity are excluded because above-ground portions carry less kavalactone and higher concentrations of undesirable constituents [32]. A flavokavain result is a chemical conformity finding about a lot and is not a statement about what a product will do for a consumer [32].

Applied to the materials examined here, all four raw powders satisfy the flavokavain specification on both of its limbs. Total flavokavains in the starting materials were 0.253% w/w for Kali-ISA, 0.260% for PNG Koniak, 0.293% for Kali-Rogu and 0.102% for Kali-Hiwa (Table 6), every value below the 0.4% w/w ceiling, and each corresponds to between 1.3% and 4.1% of the total kavalactone content of the same sample, below the 5% relative limit [30]. All four materials are therefore beverage grade on the flavokavain criterion, and the low flavokavain burden of these lots is the reason the flavokavain mass delivered per serving is small in absolute terms (Tables 3 and 4). On cultivar class the four divide. Kali-Rogu (423516) and Kali-Hiwa (463251) are kavain-led codes falling within the noble range recognized by the harmonized standards, which require a chemotype beginning 42 or 24 and admit 462 or 432 for well-documented noble cultivars [30]. Kali-ISA (254631) and PNG Koniak (256431) are dihydrokavain-led 254 and 256 codes, the profiles associated with Papua New Guinea Isa material; these are beverage grade under the flavokavain specification applied here but are not Codex noble varieties, and 256431 is the code Lebot and Lévesque recorded for the group known in Pidgin as tudei [6]. Under the classification applied here that code resolves to beverage-grade Isa rather than tudei, because both lots fall below the 0.4% w/w flavokavain limit; a 254 or 256 code is assigned to tudei only where that limit is exceeded [33]. They are accordingly reported in this paper as beverage-grade Isa-type material on the flavokavain basis, and no noble claim is made for them. The classification is a chemistry and market-access distinction rather than a safety conclusion about any cultivar [32].

2.4. Preparation of Kava Beverage

Representative 30 g portions of each dried material were milled for 30 s to a fine powder. Ten grams of powder was loaded into a 70 µm Alu Ball®, which was sealed and placed in an Alu Shaker® Pro bottle charged with 900 mL of reverse-osmosis water at 38 °C and pH 8.0. Two bottles were processed simultaneously in the two brackets of the shaker machine for a single 60 s cycle. The Alu Ball® and its contents were then either set aside for analysis of the residual marc (first-extraction condition) or returned to a second bottle charged with a further 900 mL of water under identical conditions and shaken for another 60 s (sequential-extraction condition); combined filtrates in the latter case totaled 1800 mL.

For the acidified condition, citric acid was added incrementally to the extraction water, before the Alu Ball® was introduced, until the water reached pH 5.0 as read by meter; the reading was confirmed immediately before extraction. Kali-ISA, Kali-Rogu and Kali-Hiwa were evaluated at pH 5 under the sequential-extraction protocol. The residual marc recovered from each acidified sequential extraction was air-dried to constant weight and weighed separately from its pH 8 counterpart, giving 2.94 g for Kali-ISA, 2.02 g for Kali-Rogu and 2.48 g for Kali-Hiwa against charges of 10.0 g of powder; every pH 5 mass-balance figure reported in this paper rests on those measured weights. PNG Koniak was not evaluated at pH 5. The acidified arm was exploratory and was limited to three of the four materials; because the Kali-ISA and PNG Koniak preparations were similar in chemotype and fibrous content, extending the acidified arm to both was not judged to add meaningful information.

2.5. HPLC-UV Analysis

Chromatographic separation with ultraviolet detection remains the reference approach for resolving and quantifying the individual kavalactones [34], and was used here in preference to the near-infrared and chemometric methods developed for rapid screening [35,36], which return total content or chemotype class rather than the individual compound concentrations in both beverage and marc that a mass balance requires. Individual kavalactones and flavokavains in starting materials, beverages and residual marcs were quantified by HPLC-UV at Flora Research Laboratories, LLC (Grants Pass, OR, USA) using the laboratory’s validated kavalactone method (HPLC-QNT-KAVA2), adapted from the single-laboratory-validated procedure of Liu et al. [37] and consistent with the standard method performance requirements of AOAC SMPR 2018.005 [38].

Separations were performed on an Agilent 1200 Rapid Resolution LC system with UV detection using an Agilent Poroshell 120 SB-C18 column (3.0 × 75 mm, 2.7 µm) at 55 °C. The mobile phase comprised 0.1% formic acid in water (A) and isopropanol:acetonitrile (7:3, v/v) (B), delivered at 0.40 mL min⁻¹ with a gradient from 70% A to 0% A over 10 min. Injection volume was 2 µL. Detection was at 240 nm for methysticin, dihydromethysticin, kavain and dihydrokavain, at 355 nm for yangonin and desmethoxyyangonin, and at 355 nm for flavokavains A, B and C. Identification was based on retention time and UV spectral match to authenticated reference standards obtained from Sigma-Aldrich (St. Louis, MO, USA), used for both the kavalactones and flavokavains A, B and C. Quantification used external calibration with eight-point curves (5–250 µg mL⁻¹, R² ≥ 0.999). The reporting limit for each analyte was 100 µg g⁻¹; flavokavain C was below this limit in several samples and is identified as such in the results.

2.6. Mass Balance Calculations

Mass balance was used to quantify the transfer of kavalactones from the starting material into the beverage and to distinguish kavalactones retained in the residual marc from those transferred during extraction. The dry weight of the starting material was recorded and its total kavalactone content (% w/w) determined by HPLC to give the absolute kavalactone mass present before extraction.

After extraction the residual marc was recovered, air-dried to the original constant weight (3.0% residual moisture) and weighed, and its remaining kavalactone content (% w/w) determined by HPLC. The kavalactone mass transferred to the beverage was obtained by difference:

m_KL,bev = m_KL,init − m_KL,marc and η = m_KL,bev / m_KL,init

applied both to total kavalactones and to each individual kavalactone i. The difference between the dry weight of the starting material and the dry weight of the recovered marc gave the mass of solid material that passed through the 70 µm straining vessel as suspended particulate matter. Applying the starting-material kavalactone percentage to that transferred solid mass gave the particle-associated kavalactone fraction; the remainder of the transferred kavalactone mass was taken to be truly dissolved. Combining the two steps, the dissolved mass of any analyte i is given by the identity:

dissolved_i = m_marc × (C_raw,i − C_marc,i)

where m_marc is the recovered marc dry weight and C_raw,i and C_marc,i are the concentrations of analyte i (% w/w) in the starting material and in the marc respectively. All calculations were normalized to a 3.0% moisture basis. Because mass closure depends on the difference between two independently determined concentrations, small negative solubilization values can arise where the two determinations differ by less than method precision; these are reported explicitly rather than truncated to zero.

2.7. Replication and Statistical Treatment

This study is a single-replicate mass-balance characterization: one preparation was carried out per variety per condition, and each resulting sample was assayed once, with the reported concentration being the laboratory’s mean of duplicate injections. No between-preparation standard deviations are therefore available and no inferential statistical testing was performed. Duplicate injection of a single prepared sample characterizes instrument precision, not the repeatability of the whole determination, so where the size of an analytical uncertainty is needed in this paper it is taken from the acceptance criteria of AOAC SMPR 2018.005 [38] and from the published single-laboratory validation of the procedure [37] rather than from these data. Variety-to-variety and condition-to-condition differences reported below are descriptive, and differences smaller than the analytical precision of the method should not be interpreted as real. Establishing preparation-level variability is the principal objective of the follow-on work described in Section 5.

3. Results

3.1. Total Kavalactone Extraction Efficiency

Table 1 summarizes total kavalactone extraction efficiency for the first extraction, the combined first and second extractions, and the incremental recovery attributable to the second extraction. The first extraction recovered the large majority of the available kavalactones in every variety, and the second extraction added a consistent but smaller increment.

First-extraction recovery ranged from 71.3% for PNG Koniak to 85.7% for Kali-Rogu. The incremental contribution of the second extraction ranged from 3.5% to 9.4%, and was smallest for Kali-ISA, whose marc lost the least additional mass between the two runs.

3.2. Effect of Acidification to pH 5

Table 2 compares cumulative extraction efficiency at pH 5 with the matched pH 8 condition for the three varieties evaluated under both conditions.

The direction of the pH effect was not consistent: Kali-ISA gained 3.4 percentage points, Kali-Hiwa was unchanged (89.06% at pH 8 against 89.05% at pH 5, a difference of 0.005 points that the rounded table cannot show), and Kali-Rogu lost 9.1 points. The mean effect was a net decrease, driven entirely by Kali-Rogu; Kali-ISA was the only variety to gain at all, and not by enough to offset it. The Kali-Rogu loss did not arise from less solid material passing the mesh, since its acidified marc was the lighter of the two at 2.02 g against 2.10 g at pH 8. It arose from a richer residue: the Kali-Rogu pH 5 marc assayed 5.15% total kavalactone against 1.89% for the matched pH 8 marc, so more kavalactone stayed behind in less material. Three features of this sample are difficult to reconcile with an effect of acidification on kavalactone solubility, and are reported here exactly as measured rather than adjusted or excluded. Its total kavalactone concentration after two extractions at pH 5 (5.15% w/w) is higher than that of the Kali-Rogu marc after a single extraction at pH 8 (4.05% w/w); its methysticin concentration (0.705% w/w) exceeds that of the raw starting material (0.658% w/w); and its total flavokavain concentration moved in the opposite direction to its kavalactone concentration, at 0.090% w/w against 0.164% for the matched pH 8 marc, breaking an otherwise monotonic series. No single mechanism accounts for both directions, the condition is unreplicated, and the values given are the laboratory results as reported.

3.3. Partitioning Between Particulate and Dissolved Kavalactones

Tables 3 and 4 apportion the kavalactones present in the finished beverage between those carried as suspended particulate matter through the 70 µm straining vessel and those truly dissolved, and give the delivered kavalactone and flavokavain mass in a standard 125 mL serving.

Particle-associated kavalactones accounted for 83.7–91.2% of beverage content across all varieties and both extraction protocols, with the dissolved fraction correspondingly ranging from 8.8% to 16.3%. The dissolved share was systematically higher under the combined protocol (mean 14.1%) than under the single extraction (mean 10.4%), consistent with the additional water volume and contact time favoring dissolution while the finite particulate load is divided across a larger volume. The pattern was uniform across varieties: under a single extraction every variety delivered between 87.6% and 91.2% of its beverage kavalactone as particulate matter, a spread of less than four percentage points despite a twofold range in raw kavalactone content.

Total flavokavain values for Kali-ISA, Kali-Rogu and Kali-Hiwa should be interpreted with caution because flavokavain C was below the 100 µg g⁻¹ reporting limit in the raw materials of these varieties while quantifiable in some corresponding marcs; totals for those samples therefore comprise a different set of analytes. This is the source of the small negative apparent flavokavain solubilization recorded for Kali-Hiwa, and is treated further in Section 3.5.

3.4. Dissolved Kavalactones Relative to the Starting Material

Table 5 expresses the dissolved kavalactone mass as a percentage of the kavalactone mass present in the starting material, providing the true aqueous solubilization yield of the process independent of particulate transfer.

Aqueous dissolution alone therefore accounted for a mean of only 8.1% of the available kavalactones in a single extraction and 12.2% across two, confirming that the process is dominated by mechanical particle transfer.

3.5. Compound-Level Selectivity and Chemotype

Individual kavalactone and flavokavain concentrations for every starting material and every residual marc are given in Table 6. Kavalactone rank order in the finished beverages closely tracked that of the corresponding starting materials. Kali-ISA retained its starting chemotype code (254631) unchanged under all three conditions. PNG Koniak likewise retained 256431 under both protocols. Five of the eleven beverages differed from their starting material, but these represent only two distinct transpositions, in each case of a single adjacent pair. Kali-Rogu moved from 423516 in the starting material to 423561 under both pH 8 protocols, a transposition of methysticin and desmethoxyyangonin, and returned to 423516 at pH 5. Kali-Hiwa moved from 463251 to 462351 under all three conditions, a transposition of dihydrokavain and yangonin.

Both transpositions involve compound pairs that are separated in the starting material by less than the method can resolve: methysticin and desmethoxyyangonin differ by 1.8% in Kali-Rogu (0.658% against 0.670% w/w) and dihydrokavain and yangonin by 1.4% in Kali-Hiwa (1.40% against 1.42%). Each margin is a small fraction of the 7.5% repeatability relative standard deviation that AOAC SMPR 2018.005 permits for individual kavalactones [38], and smaller than the RSDr reported for most analytes in the validation of this procedure [37]. Two compounds separated by under 2% cannot be reliably ranked against one another by this method, so their order in the beverage is not established either way and no selective extraction should be inferred from it. Consistent with this, no compound-selective extraction was resolved at the level of individual rank comparisons, and the six remaining beverages reproduced their starting chemotype exactly. Two patterns nonetheless run in a consistent direction and are reported on that basis. Desmethoxyyangonin was the most retained of the six kavalactones in the first-extraction marc of all four varieties, and both observed transpositions demoted the less water-soluble member of the affected pair. Neither pattern is established by this dataset, and both are directions that replication should be designed to test. Because the study carries no preparation-level replication (Section 2.7), statistical testing of these comparisons was not appropriate.

A small number of entries in Table 6 exceed their starting-material concentration: methysticin in the Kali-Rogu pH 5 marc (0.705% against 0.658% in the raw material), desmethoxyyangonin in the Kali-Hiwa first-extraction marc (0.652% against 0.644%), and total flavokavains in all three Kali-Hiwa marcs. Because dissolved mass is obtained as a difference between the raw and marc concentrations, an exceedance of this kind yields a small negative apparent dissolved value. Five such values occur, two of them at the level of an individual analyte and three in flavokavain totals, the largest being −0.00095 g. All are smaller than the repeatability of the analytical method at these concentrations [37,38]. The three flavokavain totals arise from the flavokavain C reporting-limit artifact described in Section 3.3, in which the total for a raw material and the total for its marc comprise different sets of analytes, rather than from analytical error as such.

These are measurement artifacts rather than chemical findings, and their size places them inside the uncertainty the method is permitted to carry. AOAC SMPR 2018.005 sets the acceptance criterion for repeatability of individual kavalactones at an RSDr of 7.5% [38], and the single-laboratory validation of the procedure used here reported RSDr values of 0.95–9.06% for kavalactones and 2.44–12.99% for flavokavains [37]. The two kavalactone exceedances are 7.1% and 1.2% of the corresponding raw-material concentration, both within that band. Where the true difference between the raw and marc concentration of a single analyte is smaller than the combined uncertainty of the two determinations from which it is calculated, the difference can take either sign as a matter of ordinary measurement scatter. A negative result in that regime carries no physical meaning. It does not indicate that kavalactone was generated during extraction, and it is equally consistent with a true dissolved mass of zero or with a small positive one that the method cannot resolve. The correct reading is that dissolution of that analyte, in that sample, was below the resolution of the measurement.

The flavokavain exceedances in Kali-Hiwa have an additional and more specific cause, set out in Section 3.3: Flavokavain C fell below the 100 µg g⁻¹ reporting limit in the raw material but was quantifiable in the marcs, so the raw and marc totals do not comprise the same set of analytes and the difference between them is not a valid mass balance. Two of the three Kali-Hiwa flavokavain differences (29% and 17% of the raw value) exceed even the 15% RSDr allowed for flavokavains in this concentration range, which is consistent with that censoring artifact rather than with random error alone.

All values are reported as measured rather than truncated at zero. Truncation would conceal the scale of the residual uncertainty and would bias the reported dissolved fractions upward, since only negative deviations would be clipped. None of these differences affects a total kavalactone balance, and the totals in Tables 3 to 5 are unaffected at the precision reported.

4. Discussion

The present study demonstrates that potency in traditional aqueous kava preparations derives predominantly from suspended particulate matter rather than from aqueous solubilization of kavalactones. Across all varieties and both protocols, 84–91% of the kavalactones present in the beverage were particle-associated, with dissolution accounting for 9–16%. This is consistent with the low aqueous solubility of the individual kavalactones [22–24] and highlights the decisive influence of filtration pore size on beverage potency and chemistry. The 70 µm straining vessel produced a consistent particle suspension, reproducing the defining characteristics of traditionally prepared beverages while minimizing operator-dependent variability.

The dissolved fractions measured here can be checked directly against those solubility figures. In the single extraction, 10 g of powder was extracted into 900 mL of water, so the dissolved kavalactone masses behind Table 5 correspond to aqueous concentrations of 11.4 mg per 100 mL for Kali-ISA, 8.4 for Kali-Rogu, 6.6 for PNG Koniak and 6.4 for Kali-Hiwa. The compiled 21 °C solubilities sum to 13.8 mg per 100 mL [24,25], equivalent to a saturation ceiling of roughly 124 mg of dissolved kavalactone in 900 mL. Every variety falls below that ceiling, at 46–83% of it, and none exceeds it. Because the kavalactone available in the starting material exceeded the ceiling several-fold in every case — 707 to 1,424 mg against 124 mg — the aqueous phase was not supply-limited, and the dissolved fraction is bounded at the level of the total by solubility rather than by the efficiency of the preparation. That bound applies to total kavalactone and not to every compound taken individually: measured against the same compiled figures, dissolved yangonin exceeds its tabulated 0.3 mg per 100 mL ceiling in all four varieties, and four of the six kavalactones exceed theirs in Kali-ISA, which is consistent either with very fine particulate being counted as dissolved or with the compiled single-compound values being too low. Two consequences follow. First, the inverse relationship between starting content and dissolved percentage is expected rather than anomalous: Kali-ISA carried nearly twice the kavalactone of Kali-Rogu yet returned a lower dissolved percentage of its starting material (7.2% against 10.7%, Table 5), because the numerator is capped while the denominator is not. Second, no adjustment to shaking time, agitation intensity or water temperature within the range used in practice can raise the dissolved fraction more than marginally, because there is little headroom left to exploit. One caveat applies: the solubility values are reported at 21 °C whereas extraction here was carried out at 38 °C, so the true ceiling during extraction was higher than 124 mg and the measured fractions sit correspondingly further below it.

This also bears on a long-standing interpretation in the pharmaceutical literature. Cold aqueous macerates were observed to carry up to approximately 70 mg of total kava pyrones per 100 mL against a measured kavain solubility of 2.2 mg per 100 mL at 21 °C, and the discrepancy was attributed to inert matrix constituents acting as solubilizers [39]. The present mass balance offers a simpler explanation for the bulk of that gap: in these beverages total kavalactone concentration reached 118 mg per 100 mL for Kali-ISA while the dissolved concentration was 11.4 mg per 100 mL, so the excess over the solubility limit was not dissolved at all but suspended. Matrix-mediated solubilization may still contribute at the margin, since the dissolved concentrations measured here sit at or slightly below the summed solubility figures rather than above them; but no solubilization mechanism is required to account for a beverage carrying ten times more kavalactone than water alone can hold.

Sequential extraction clarified the relationship between efficiency and dilution. The second extraction consistently recovered further kavalactones from the marc (mean 7.7%), raising cumulative yield to 85.5%. That gain was offset by the additional water, reducing beverage strength from a mean of 100 mg to 55 mg of kavalactones per 125 mL serving. The trade-off is a practical constraint on any attempt to maximize recovery: sequential extraction improves total yield while diminishing per-serving intensity. For both consumer and research contexts the distinction between absolute yield and per-serving potency is therefore essential in determining preparation practice.

From a production standpoint the distinction has direct economic implications. Where cost efficiency and maximal raw-material utilization are the priority, a two-stage extraction is advantageous, since the additional recovery materially increases total kavalactone yield per unit of starting material. Where per-serving potency, immediate sensory impact and dose consistency are the priority, a single extraction is preferable. Controlled consumer-preference studies comparing single- and sequential-extraction beverages would quantify the perceived difference and provide empirical support for this trade-off.

Individual kavalactone profiles in the beverages closely mirrored those of the starting materials (Table 6, Section 3.5), with such rank changes as occurred confined to adjacent and narrowly separated compounds. This contrasts with concurrent work by the present authors using a commercial blender to perform three sequential warm-water extractions of fresh-frozen material, in which chemotype shifts were observed in some varieties [27]. While the present study was not designed to explain such differences mechanistically, the divergence suggests that extraction mechanics — shear force, particle disruption and filtration behavior — may exert a stronger influence on selective kavalactone partitioning than water temperature or extraction duration alone.

The kavalactone content of the residual marcs illustrates the inherent limits of aqueous extraction. On a mass-balance basis, 25.8% of the starting kavalactone mass remained in the Kali-ISA marc after a single extraction and 22.3% after two, with corresponding figures of 28.7% and 19.3% for PNG Koniak; Kali-Hiwa retained 19.9% and 10.9% and Kali-Rogu only 14.3% and 5.6%. The marcs were also depleted in concentration terms, though never exhausted: the first-run Kali-ISA marc assayed 11.14% w/w against 14.24% w/w in the raw material (78% of the starting concentration) and the second-run PNG Koniak marc 4.89% w/w against 7.97% w/w (61%). Solid retention in the straining vessel fell within a narrow band across the four varieties, from 25.0% of the charged dry mass for Kali-Rogu to 36.2% for PNG Koniak, with Kali-Hiwa at 27.0% and Kali-ISA at 33.0%. Retention of solids and retention of kavalactone track each other closely across this range: Kali-Rogu, which passed the most solid material through the mesh, also gave up the most kavalactone, while PNG Koniak retained the most of both.

Two mechanisms may plausibly contribute to this retention, though neither was measured here. Concurrent leaching of starch and other water-soluble solids into the beverage would raise the relative kavalactone concentration in the remaining matrix, and the comparatively fibrous tissue structure of Kali-ISA and Koniak may present binding sites that impede kavalactone release into water. Both remain hypotheses: testing them would require quantification of the non-kavalactone dissolved solids load and of tissue composition, which the present design does not provide. The constraints imposed by solubility and tissue structure nonetheless point to controlled pH adjustment, enzymatic treatment and modified particle-size reduction as avenues for improving recovery.

Kali-ISA exhibited a distinct profile of high kavalactone content with comparatively low flavokavain content. It delivered the highest kavalactone concentration per 125 mL serving under single extraction (147 mg) while total flavokavains remained at 2.6 mg. Under sequential extraction it continued to compare favorably, delivering approximately 77 mg of kavalactones per serving with flavokavains declining to 1.3 mg. Normalized to 100 mg of kavalactones, Kali-ISA carried well under half the flavokavain load of Kali-Rogu (1.7 mg versus 4.1 mg). Subject to the caveat on flavokavain C in Section 3.3, to the eighteen-month age of the Kali-ISA plant against three years for Kali-Rogu and Kali-Hiwa, which confounds variety with maturity throughout any comparison involving this variety (Sections 2.2 and 5), and to the reporting of Kali-ISA as beverage-grade Isa-type material for which no noble claim is made (Sections 2.3 and 5), this profile may have organoleptic relevance, since higher kavalactone concentrations contribute to perceived strength and mouthfeel while lower flavokavain levels may reduce the bitterness and astringency reported by consumers. It underscores the importance of varietal selection alongside standardized preparation in shaping both chemical outcomes and sensory experience.

Acidification to pH 5 did not consistently increase total kavalactone extraction efficiency relative to pH 8 under this method (Table 2). Mean cumulative efficiency at pH 5 (85.1%) was lower than that at pH 8 (87.0%), with only Kali-ISA showing a modest enhancement of 3.4 points. This was unexpected given concurrent findings by the present authors that lowered pH may improve kavalactone solubilization under a commercial blender method applied to fresh-frozen material [27]. The absence of a broad pH effect here suggests that within this preparation framework extraction efficiency is governed more strongly by mechanical particle transfer and filtration dynamics than by modest changes in aqueous chemistry — reinforcing the central conclusion that particulate suspension rather than true solubilization drives kavalactone delivery. The largest single deviation, a 9.1-point decrease for Kali-Rogu, rests on separately measured marc weights at both pH values but is unreplicated, and should be treated as provisional on that ground alone.

5. Limitations and Future Work

The principal limitation is the absence of preparation-level replication. Each variety was prepared once per condition, so no estimate of between-preparation variability is available and the reproducibility that this method is intended to deliver is asserted from its mechanical design rather than demonstrated from the data. Quantifying that variability across independent preparations is the first priority for follow-on work and is a prerequisite to any claim of superiority over manual preparation. This is distinct from analytical repeatability, which the published validation of the analytical method does constrain (Section 3.5); the missing quantity is the variability contributed by the preparation itself, and it is the larger of the two unknowns.

The study was further constrained to a single extraction temperature and two pH levels, limiting resolution of temperature–pH interaction effects on partitioning and solubilization, and PNG Koniak was evaluated at pH 8 only. Future work will evaluate a broader temperature range and finer pH gradients, and will extend the dataset to a wider set of commercial Pacific and field-grown American kava samples to strengthen external validity and assess how cultivar handling and supply-chain variability influence beverage chemistry under standardized preparation.

Direct comparisons between the Alu Bottle Shaker® method and other approaches reported in the literature — traditional manual kneading, blender-based aqueous extraction and sonication-assisted extraction — are needed to contextualize extraction efficiency, chemotype stability and compound selectivity. The starch-leaching and tissue-binding mechanisms proposed in Section 4 remain untested and require quantification of dissolved non-kavalactone solids.

A further limitation concerns the marc dry weight, which is a primary gravimetric measurement and therefore an independent source of uncertainty in the mass balance. Because the dissolved kavalactone mass is the product of the marc dry weight and the difference between the raw and marc kavalactone concentrations, it scales linearly with that weight, and extraction efficiency, particulate share and per-serving potency all depend on it directly. No quantity measured by HPLC-UV can constrain it independently, so the accuracy of the reported efficiencies rests on the gravimetry alone. Each weight here derives from a single determination; replicate weighing of the marcs, together with a sieve analysis relating retained mass to the 70 µm pore size, would place formal bounds on this term and is recommended for follow-on work.

The acidified condition carries one further constraint. The extraction water was titrated to pH 5.0 rather than dosed with a fixed quantity of citric acid, so the acid concentration of the water differed between varieties according to the buffering capacity of each material and was not recorded; the pH 5 condition is therefore reproducible as a pH endpoint but not as a defined acid concentration. The marc dry weights for the acidified condition were determined separately, by the same gravimetric procedure applied to the pH 8 marcs (Section 2.4), so the pH 5 columns of Table 2 rest on measured rather than inferred masses. What the pH 5 comparison lacks is not gravimetry but replication, in common with every other condition reported here.

Plant age at harvest was not uniform. The Kali-Rogu and Kali-Hiwa plants were three years old while the Kali-ISA plant was eighteen months old (Section 2.2), so differences involving Kali-ISA confound variety with maturity. Since Kali-ISA carried both the highest kavalactone concentration and the highest solid retention, the possibility that maturity rather than cultivar identity drives part of its behavior cannot be excluded from this dataset, and matched-age material is needed to separate the two. Growing site and plant age are established determinants of total kavalactone content in kava [7], so this is a substantive confound rather than a formal caveat.

The partition calculation additionally assumes that solids passing the 70 µm mesh carry the same kavalactone concentration as the bulk starting material. If the fine fraction is enriched in resinous, kavalactone-bearing tissue, the particle-associated share reported here is an underestimate and the dissolved share a corresponding overestimate. Direct assay of the recovered fine particulate fraction would test this assumption.

The identity determination carries its own limits. HPTLC against authenticated reference material combined with the HPLC-UV chemotype (Section 2.3) establishes that the three American cultivars produce the expected Piper methysticum banding pattern and a kavalactone rank order consistent with cultivated varieties rather than wild forms, and the flavokavain results place all four materials inside the beverage-grade specification. What that combination does not do is assign a formal nobility classification. Noble status under the Codex regional standard rests on cultivar identity confirmed by morphological characteristics [29], and its analytical confirmation calls for marker-based or chemometric methods — SSR genotyping, FTIR chemometrics, or the acetonic absorbance test of the Codex standard, which passes at or below 0.9 absorbance units — none of which was applied here [14,29]. The American accessions are therefore reported as identified P. methysticum of cultivated type and of beverage grade, not as certified noble cultivars, and Kali-ISA and PNG Koniak are reported as Isa-type material for which no noble claim is made. The Papua New Guinea material was a commercial dried batch and was not HPTLC identity-tested, so results attributed to “Koniak” describe the batch as received rather than a verified cultivar. SSR genotyping of the American accessions, acetonic absorbance testing, and identity screening of any comparative commercial material are planned for the follow-on work.

Finally, this study did not assess sensory perception or consumer response. Given that particle load, dilution, pH and extraction intensity may all influence mouthfeel, flavor and perceived potency, future work should integrate structured sensory evaluation and consumer preference testing to link measured kavalactone profiles with experiential outcomes.

6. What These Findings Mean in Practice

The results have direct consequences for anyone who grows, prepares, sells or regulates traditional aqueous kava. They are set out here separately from the scientific discussion because they do not depend on accepting any particular interpretation of the chemistry — they follow from the mass balance itself.

6.1. For Preparers and Kava Bars

Strainer pore size and grind fineness are the primary determinants of beverage strength, ahead of water temperature, shaking time or pH. Because roughly nine parts in ten of the delivered kavalactone travels as suspended particulate, any change that alters how much fine solid passes the mesh changes potency proportionally, while changes intended to improve dissolution have little to work with. A bar that standardizes its strainer and its grind has standardized most of the variability in its product; one that standardizes water temperature alone has not.

Sequential re-extraction is a yield decision, not a strength decision. Running a second charge of water through the same spent root recovers a further 7.7% of the available kavalactone on average, but because that yield is diluted across twice the water, per-serving strength falls by roughly half. Whether that trade is worth making depends on whether the operation is optimizing cost per gram of root or consistency of dose per cup. It cannot optimize both at once.

Suspension behavior also means that settling matters. If most of the active material is particulate, a beverage that has been standing will not be uniform, and a serving drawn from the top of an unstirred vessel will not carry the same dose as one drawn from the bottom. Consistent agitation before pouring is a dose-control measure, not a matter of presentation.

6.2. For Producers and Product Developers

Label claims about kavalactone content in a traditional aqueous product are claims about particle transfer. A stated milligram figure per serving is only reproducible if pore size, grind, water volume, temperature, agitation and the number of extraction passes are all fixed and disclosed, because each of those variables moves the figure. Stating the kavalactone content of the root without stating the preparation parameters says little about what reaches the consumer.

Chemotype survives preparation substantially intact. Rank order in the beverage tracked the starting material closely across all four varieties, with changes confined to adjacent positions. Selecting a variety for a particular kavalactone profile is therefore a meaningful decision, and the profile a grower selects for is broadly the profile a drinker receives — which is not something that could be assumed before it was measured.

Flavokavain content, normalized to kavalactone delivered, differed markedly between varieties, ranging from about 1.0 to 4.1 mg per 100 mg of kavalactone in a single extraction. For producers who wish to minimize flavokavain exposure on the precautionary grounds discussed in Section 4, variety selection is a more effective lever than preparation method.

6.3. For Regulators and Standards Bodies

Any specification for traditional aqueous kava that regulates only the composition of the raw material is incomplete, because the same root prepared two ways delivers materially different doses. A workable specification must fix the preparation parameters or state the dose as a range conditional on them. The parameters that need fixing are identified above; the mechanical system used here fixes all of them and is offered as one way of doing so, not as the only one.

Analytical methods applied to finished aqueous kava must account for the particulate fraction. A method that assays only the filtered liquid will report between 8.8% and 16.3% of the kavalactone a consumer actually receives — roughly one tenth under a single extraction and nearer one seventh under the combined protocol. This is a substantial and systematic underestimate, and it applies to any compliance testing, potency verification or exposure assessment carried out on traditional aqueous preparations.

6.4. What This Paper Does Not Establish

The findings rest on one preparation per variety per condition, with the mass balance anchored to marc dry weights that were each determined once. The paper therefore establishes the magnitude and direction of the particulate effect, which is large enough to be robust to plausible weighing error, but it does not establish the precision of any individual figure, and does not demonstrate reproducibility across independent preparations. Section 5 states each limitation in full. Readers should treat the particulate finding as established and the specific percentages as best current estimates awaiting replication.

7. Conclusions

Standardized mechanical preparation using the Alu Bottle Shaker® produces traditional aqueous kava beverages whose potency and chemotype are governed primarily by suspended particulate matter rather than by true aqueous solubilization of kavalactones. Under the conditions tested, a single extraction recovered a mean of 77.8% of the total kavalactones in the starting material and sequential re-extraction raised cumulative recovery to a mean of 85.5%, confirming that the majority of kavalactone transfer occurs during the initial preparation cycle. Aqueous dissolution alone accounted for only 8.1% of the starting kavalactones in a single extraction.

The increase in total recovery came at a predictable cost in per-serving potency. Single-extraction beverages delivered a mean of 100 mg of total kavalactones per 125 mL serving, whereas combined first and second extractions reduced this to a mean of 55 mg per 125 mL, illustrating the trade-off between cumulative yield and per-serving intensity. The distinction is directly relevant to consumer experience and to product safety, and extraction efficiency metrics must therefore be interpreted alongside serving-level potency rather than in isolation.

By fixing pore size, shaking time, water volume and water temperature, the method removes the principal sources of operator-dependent variability inherent in manual preparation with cloth strainers, and so offers a defined and transparently documented basis for comparative kava research, commercial production and regulatory evaluation. Demonstrating the reproducibility that this design implies, across independent replicate preparations, is the necessary next step.

Supporting Data and Materials

The following are available from the corresponding author: the fifteen HPLC-UV analytical reports; the mass-balance workbook containing the per-variety extraction sheets, the master table of recorded dry weights, an internal mass-closure check and a log of all corrections applied during preparation of this paper.

Funding and Authorship

This work received no external grant funding. Analytical costs were borne by the authors. Equipment and materials were donated as described under Disclosures and Conflicts of Interest. T.B. designed the study, performed the extractions, carried out the mass-balance analysis and prepared this paper; T.B. and J.B. contributed to the method design and to review and editing. Both authors have read and approved this paper. The study involved no human or animal subjects.

Data Availability

The complete set of fifteen HPLC-UV analytical reports issued by Flora Research Laboratories (job identifiers J25-0930-H and J25-0930-I), together with the recorded sample and marc dry weights and the mass-balance worksheets underlying Tables 1–6, are released as supporting material with this paper and are available from the corresponding author or from the American Kava Association on request.

Supplementary Materials

Supplementary files are available from the corresponding author on reasonable request.

Institutional Review Board Statement

Not applicable. This study did not involve humans or animals.

Informed Consent Statement

Not applicable.

Acknowledgments

The authors thank Flora Research Laboratories, LLC (Grants Pass, OR, USA) for analytical services, and Kavafied, the American Kava Association and Root of Happiness for the donations described below.

Use of Generative Artificial Intelligence

Generative artificial intelligence was used in the preparation of this manuscript. Claude Opus 4.6 (Anthropic) was used to compile study data into tabular form, to construct the manuscript tables, and to perform arithmetic checks of the reported calculations. All compiled values and derived calculations were independently verified by the authors against the source records. ChatGPT 5.2 (OpenAI) was used for grammar and language editing only. No data were generated, imputed, or interpreted by generative artificial intelligence.

Disclosures and Conflicts of Interest

The authors declare the following interests, and readers should weigh the findings in light of them. Both authors are commercially engaged in the kava trade. Kavafied is the manufacturer of the equipment under evaluation, which manufactures and sells the Alu Bottle Shaker® machine, the 70 µm Alu Ball® straining vessel and the Alu Shaker® Pro bottle evaluated here, and which donated that equipment for this study; Kavafied therefore stands to benefit commercially from favourable findings about the system. T.B. is affiliated with Root of Happiness, which donated the Papua New Guinea “Superior Koniak” material, was the named client on the analytical reports commissioned for this study and provided financial support, and in which T.B. holds an ownership interest. T.B. is also affiliated with Kali-Kava who donated the Kali-Hiwa, Kali-ISA, and Kali-Rogu material. J.B. is affiliated with Nakamal at Home, a kava retailer. The American kava materials were donated by the American Kava Association, and were grown by T.B. The corresponding author is additionally a contributing author of AOAC SMPR 2018.005 [38], cited in Section 2.5. This paper is published by the American Kava Association, which also donated the American kava materials and maintains the research greenhouse in which they were grown, and the authors are members of that organization; readers should weigh the findings accordingly. None of these parties participated in the analysis or in the generation of the data, which were produced by an independent accredited laboratory from samples submitted blind to the interpretations offered here. The paper reports what the system delivered under one set of conditions and does not compare it against any competing preparation method; no claim of superiority over manual preparation or over any other device is made or supported here (Section 5).

Alu Bottle Shaker®, Alu Ball® and Alu Shaker® are registered trademarks of Kavafied. Trademarks are acknowledged at each use in this paper and their use does not imply endorsement of this paper by the trademark owner beyond the disclosures given above.

Abbreviations

DHK dihydrokavain

DHM dihydromethysticin

DMY desmethoxyyangonin

FK flavokavains (total)

HPLC-UV high-performance liquid chromatography with ultraviolet detection

K kavain

KL kavalactones (total)

LOD limit of detection

LOQ limit of quantitation

M methysticin

PT KL particle-associated kavalactones

RSDr repeatability relative standard deviation

WS KL water-dissolved (solubilized) kavalactones

Y yangonin

Editorial process

Tyler Blythe is the founder of the American Kava Association, which publishes this journal, and is the journal's Editor-in-Chief; he handled this manuscript. Before acceptance the manuscript underwent Computational Manuscript Review (CMR; see editorial policies) and was then accepted on the editor's decision. No editorial review independent of the authors took place. Corrections, if any, are issued as dated notices linked from this page; the version of record is not amended silently.

References

About the American Kava Association

The American Kava Association supports the cultivation, study and responsible commerce of kava in the United States. It maintains research stations in Sacramento, California, and Boca Raton, Florida where the American varieties described in this paper were grown, and it publishes technical white papers to place primary data before growers, producers, regulators and the drinking public.

This paper is American Kava Association Technical White Paper No. 5, version 1.0, released August 2026. Correspondence and requests for the underlying data should be directed to admin@americankavaassociation.org. The paper may be reproduced and distributed in full only with proper attribution; excerpts should cite the suggested citation given on the cover.

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How to cite

Blythe, T.; Bowman, J. Standardized Preparation and Extraction Efficiency of Traditional Aqueous Kava Beverages. J. Am. Kava 2026, 1, 005. https://journalofamericankava.org/articles/alu-shaker-extraction

Please cite this version of record. The earlier preprint (10.5281/zenodo.22839212) is superseded by it.