# Hazelnut press cake becomes a candidate ingredient for water kefir

> A fermentation trial finds that added sugar changes stability, texture and volatile profiles; reduced ELISA reactivity does not establish safety for people with hazelnut allergy.

URL: https://foodradar.org/hazelnut-press-cake-water-kefir-fermentation
Language: en
Author: FoodRadar Editorial
Published: 2026-10-07T11:21:42.823Z
Updated: 2026-10-07T11:21:42.823Z
Source publication date: 2026-08-31
Category: Industry
Türkçe: https://foodradar.org/tr/hazelnut-press-cake-water-kefir-fermentation

## Giving an oil-processing residue another use

Hazelnut press cake can provide the base for a fermented beverage, according to an August study that combined high-pressure homogenisation with water-kefir fermentation. The researchers compared three added-sugar levels with a no-added-sugar control. A 5% addition gave the most balanced water-holding and physical-stability results, while higher sugar altered viscosity and microbial activity.

The material was the cake left after shell removal and cold-press oil extraction. It was ground, dispersed in water at 10% mass per volume and homogenised at 100 MPa. The resulting hazelnut beverage then served as the fermentation medium. The work demonstrates one laboratory route for using that residue; it does not establish the economics or environmental balance of a commercial upcycling operation.

## Sugar changed more than sweetness

Activated water-kefir grains were added to the plain beverage and to formulations containing 2.5%, 5% or 7.5% sucrose. Fermentation lasted 72 hours at 25 °C, followed by overnight refrigeration before analysis. Three independent fermentation batches were produced. The comparison consequently captures a defined production endpoint, rather than an extended refrigerated shelf-life study.

Sugar addition increased the measured populations of several fermentation organisms and affected the beverage’s flow properties. The samples behaved as pseudoplastic fluids, meaning viscosity decreased under greater shear. The 5% treatment led the combined physical-stability assessment, while additional sugar generally increased viscosity. Those results help define formulation choices, but they do not identify one universally preferred sugar content for all markets or nutritional objectives.

## Aroma percentages are not alcohol by volume

The researchers tentatively identified 47 volatile compounds using GC–MS library matching. Increasing sugar changed the relative contributions of ethanol, acetic acid and other compounds to the volatile profile. However, the reported percentages were normalised chromatographic peak areas, without an internal standard; they were not absolute concentrations.

In particular, the ethanol percentages in that analysis cannot be read as the drink’s alcohol by volume. Compound identities also remained tentative because authentic standards and retention-index confirmation were not used. A commercial beverage specification would need measurements suited to the final product, rather than converting relative aroma signals into an alcohol-content or labelling claim.

## The allergen result needs careful interpretation

The study measured hazelnut-protein immunoreactivity with a commercial ELISA assay. The starting beverage gave a value of 16.6 micrograms per millilitre, compared with 8.42–12.97 in the fermented samples. Lower assay reactivity is a laboratory observation; it does not show that the beverage is safe for a person with hazelnut allergy, and the experiment did not establish clinical tolerance.

Chemical antioxidant measurements likewise concern the beverage, not a demonstrated health effect in consumers. The authors call for further work on fermentation behaviour and storage stability. For ingredient and beverage companies, the useful outcome is a candidate process with measurable formulation trade-offs. Shelf life, product consistency, actual alcohol content and the implications of retaining hazelnut proteins all remain essential parts of subsequent product validation.

## Sources and rights

- [Potential Use of Hazelnut Beverage in Water Kefir Fermentation: Effects of Sugar Addition on Physicochemical, Microbiological, Rheological, Bioactive, Volatile, and Allergenic Properties.](https://europepmc.org/articles/PMC13527763?utm_source=foodradar.org&utm_medium=referral&utm_campaign=editorial&utm_content=hazelnut-press-cake-water-kefir-fermentation-en). Journal of food science. Gul LB, Akgun A, Gul O. Potential Use of Hazelnut Beverage in Water Kefir Fermentation: Effects of Sugar Addition on Physicochemical, Microbiological, Rheological, Bioactive, Volatile, and Allergenic Properties. Journal of food science. 2026. DOI: 10.1111/1750-3841.71432. © 2026 The Author(s). Journal of Food Science published by Wiley Periodicals LLC on behalf of Institute of Food Technologists. [CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/?utm_source=foodradar.org&utm_medium=referral&utm_campaign=editorial&utm_content=hazelnut-press-cake-water-kefir-fermentation-en-license).

Adapted by FoodRadar.

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