Biomodification of a plant base from cereal flour to produce an alternative fermented drink

摘要

Background: Cereals are the most promising raw material for producing functional fermented drinks. Buckwheat possesses a unique chemical composition, high nutritional value, and significant physiological activity. However, cereals lack easily digestible sugars and nitrogen compounds for lactic acid bacteria. 

Objective: The study focused on determining whether enzymatic hydrolysis of buckwheat flour can provide a cereal base with soluble sugars and free amino nitrogen to support the rapid growth of lactic acid bacteria and improve the sensory characteristics of fermented products.

Methods: The grain base was obtained from buckwheat groats. The groats were ground into flour. The granulometric analysis of the flour was conducted using a laser analyzer. Flour samples with different particle sizes were hydrolyzed with α-amylase, protease, and glucoamylase. The hydrolysis temperature was selected based on the temperature at which the viscosity of the flour-water mixture reached its maximum. The hydrolysates' solids, sugars, and free amino nitrogen were analyzed using refractometry, HPLC, and spectrophotometry. The buckwheat bases were fermented with L. acidophilus and L. plantarum. The number of lactic acid microorganisms in the fermented bases was determined by the plate count method on MRS agar. Sensory properties (taste, aroma, and texture) were evaluated using a developed 5-point scale.

Results: The study found that hydrolysis of buckwheat flour using α-amylase, protease, and glucoamylase produced a cereal base with 19.15±0.05 g/L glucose, 29.54±0.06 g/L maltose, and 104.72±0.15 mg/100 g of free amino nitrogen. The biomodification resulted in changes to the cereal base composition, favorable for developing lactic acid bacteria cultures. During fermentation of the biomodified base with L. acidophilus, a pH level of 4.5 ± 0.1, a cell count of 10⁸ CFU/g, and high taste and aroma scores were achieved within 5 hours. For L. plantarum, the changes ensured a pH of 4.5 ± 0.1 and a cell count of 10⁷ CFU/g after 7 hours, but lactic fermentation's characteristic taste and aroma were not pronounced. 

Conclusion: The buckwheat flour was processed by grinding groats and using enzymatic hydrolysis with α-amylase, protease, and glucoamylase, resulting in a cereal base with a promising composition for the following fermentation. Additionally, the approach offers a model for processing other cereals, contributing to developing alternative plant-based fermented beverages with enhanced functional and sensory properties. 

Keywords: buckwheat flour, cereal-based fermented beverage, dairy alternatives, enzymatic hydrolysis, lactic acid bacteria, fermentation.