We’ve recently published a couple of guest posts covering the science of traditional kava preparation. So far we’ve focused on the questions of optimal number of washes (the effect of re-using the same roots in new water) and the optimal kava kneading time. Judging by the feedback we’ve received our readers find these posts quite helpful, so our friends at Root & Pestle have kept digging into more questions related to traditional kava preparation. In today’s guest blog post they explore another interesting question: what is the best temperature for preparing kava? As you may know, the Australia New Zealand Food Standards Code specifies that kava should be prepared using “cold water”, which is a fairly vague term that most people understand as anything between ice cold and cold enough to touch (i.e. not boiling!). In our view, it was intended to mean temp at which kava had been traditionally prepared on the islands of the South Pacific. This is warmer than New Zealand room temperature (which would be around 18-20C) as most islands enjoy hot tropical climates, so cold water in such climates can be closer to 25-30C. We have thus been recommending using water at “lukewarm”/body temperature. In our experience water temperature of around 30C produces the best results. But Forney/Root & Pestle research team has decided to dig deeper and study carefully how different temperatures affect the potency and quality of kava. As last time, while they confirmed our non-scientific assesment, they’ve discovered a few surprises!

Water Temperature: New Insights into Optimising the Squeeze revealed by Forney Enterprises and Root & Pestle R&D

The majority of the kavalactone content in traditionally prepared kava lies in the sediment that settles out of the drink. After scrutinising hundreds of kava preparations (and thousands of kavas) in our lab (with 36 unique samples prepared and analysed by UHPLC just for this investigation into the effect of water temperature on kavalactone extraction efficiency), we can say this with certainty. This is why stirring the natambea/tanoa is essential before dishing out each and every shell to distribute the kavalactones evenly from serving to serving.

Using hotter water during the squeeze objectively yields much higher sediment content than using colder water. This is abundantly evident when many samples prepared the same way (except for water temperatures) are lyophilised (controlled removal of the water by sublimation at low temperatures and pressures) - The volume of residual material in each vial noticeably rises from the one before, stepwise, in direct relation to the temperature used to prepare the sample.

When we centrifuge our samples at extreme g-forces for extended durations and subsequently separate and lyophilise the supernatant (examining the “water layer” instead of the sediment), we observe the same trend. Not only does hot water extract far more sediment, but it also extracts significantly more soluble material and nanometer-scale particles; Lyophilised supernatant from ice-cold extractions results in nearly empty vials, while lyophilised supernatant from very hot extractions results in vials that are still full to the brim, holding the shape of the material which was dissolved in the water even after the water is frozen and sublimated away.

Hot water extracts more material from traditional kava powder into the resulting beverage than using cold water does. There is no reasonable doubt or debate about it.

Given these observations, and especially when taken in conjunction with the plethora of comments online stating the importance of using warm (or even hot) water during the squeeze, one could be forgiven for assuming that more sediment (and more dissolved material) equates to more kavalactones, but interestingly, we found that the total kavalactone content remained more or less unchanged, regardless of the amount of sediment or whether the squeeze was done with ice water or at temperatures so hot that starch gelatinisation occurred, resulting in thick, gooey kava that most would find truly unpalatable (or at temperatures anywhere in between); The ratio of kavalactones to sediment decreased with rising extraction temperatures.

However, performing the squeeze with different water temperatures did result in making different kavas, for more reasons than just the sediment content:

The chemotype of the prepared beverages closely reflected the chemotype of the traditional powder used to make it, regardless of water temperature, but it was not an exact parallel; We noticed that the kavain to dihydromethysticin ratio (K:DHM) and the kavain to dihydrokavain ratio (K:DHK) showed a slight, but clear downward trend as water temperatures increased. The accompanying graph shows the smoothed trendlines.

Squeezing kava with ice water yielded a chemotype closer to one potentially associated with more euphoric effects, while hot water squeezes produced chemotype changes leaning towards the calming side of the spectrum, although the differences were not substantial.

Kavain is often characterised as being the compound most responsible for kava’s ability to induce “headiness”. Dihydromethysticin is often cited as being at the opposite end of the spectrum – it is metabolised more slowly and is generally regarded as being a major contributor to the “heavier” side of the subjective kava experience. In many respects, dihydrokavain is often thought of as being somewhere between kavain and dihydromethysticin in terms of its psychoactive effects. It is worth noting here, however, that the experience might best be viewed as a result of the synergy among the combined molecular orchestra at play, rather than attributing any specific effect to a single compound.

Nevertheless, these findings suggest that not only will kava squeezed in cold water be lighter in texture with substantially less sediment, but that it may also alter the resulting subjective psychoactive experience, perhaps nudging it slightly more in the direction of euphoric, whilst using hotter water may lean the imbiber slightly towards feelings which might be a bit closer to the soporific, although we did not follow this supposition up with pharmacological assays.

In any case, the overall chemotype of the beverage most closely approximated the parent powder when prepared in water somewhere in the temperature range of 25 to 45 °C (77 to 113 °F), although as we mentioned earlier, the observed variations to chemotype were subtle at all temperatures investigated.

Organoleptically, we found that not only did the texture change with rising squeeze temperatures (first becoming beautifully creamy as we rose through room temperature, but then thickening beyond desirability above 40 °C (104 °F)), but the taste changed too. The distinctive pepperiness of the kava coincided with the preparation temperature, becoming particularly pronounced above 30 °C (86 °F). At cold temperatures, there was no bitterness perceived at all, but it was abundantly evident by about the 35 °C (95 °F) mark, and by 42.5 °C (108.5 °F) we found the taste to be rather unpleasant. Our team described kava prepared at temperatures above this as, “nasty”, but only you can decide your own taste preferences.

We are accustomed to drinking kava at the local nakamals here in Vanuatu, where spring water, rainwater, or sometimes river water is used to prepare the kava. These all feel somewhat cool to the touch at first, but by the time they are collected and brought to the point where the squeeze takes place, they’ve usually warmed up to about the ambient temperature, which is typically around 28 °C (82.4 °F) towards the last half of the afternoon, when most kava sessions in this part of Northern Vanuatu begin to kick off.

Because of this, to us, the kava experience is most authentic when we can closely emulate what we’re used to, and this happens when we squeeze with water in the range of 25 to 30 °C (77 to 86 °F). If you want a lighter kava that some may find a little easier to drink, you can try using cooler water without worrying that you’re losing out on a significant amount of the available kavalactones, however, it needs to be said that there may be other compounds in the sediment which potentiate the experience, and we did not investigate the pharmacology of the finished products in this experiment, we just quantified the kavalactone content.

We also did not standardise the temperature of our prepared kavas before consumption, but we can tell you from experience that most people find kava easier to drink when chilled. At some nakamals in Vanuatu, or sometimes on special occasions, they will put a few bottles filled with frozen water into the serving bowl (after squeezing), thus chilling the kava without diluting it. Many people find they enjoy being served kava this way, although it is somewhat less common in Vanuatu than simply drinking the kava warm.

On a related note, despite kava’s documented antimicrobial properties, and despite the fact that pathogens do not tend to grow in kava powder if it was processed properly, appropriately pasteurised and with the moisture content reduced to a sufficiently low concentration, once prepared, certain bacterial species can colonise the mixture, turning it sour. This happens much more slowly when the kava is cold, so if you are creating a large batch which you intend to serve over the course of hours or longer, keeping it chilled may be worth considering.

By sharing our understanding of the nuances of kava, we hope to empower better tailoring of the experience to individual preferences whilst maintaining its authenticity. We hope this investigation enhances your appreciation of kava's complexity and provides some insight into your own preparation techniques. Thank you for joining us on our exploration of this incredible plant!