Paulina Pawłowska, M. Sc., Eng.
LOW ALCOHOL BEVERAGES FROM OATS WITH PRO-HEALTH PROPERTIES
Summary
The main objective of this research was to develop the basics of the production of oat fermented beverages, addressed mainly to people remaining on gluten-free diet, who are not allowed to consume beer.
The use of oats in brewing was an innovative solution, due to the nature of this raw material. Therefore, it was necessary to modify classical brewing technology at each stage of beverage production, in particular the malting and mashing processes, to obtain a product with acceptable organoleptic qualities.
The initial stage of the study was to choose the best oats variety on the base of its chemical composition and physiological condition, which were the most similar to the parameters of brewing barley. Based on the conducted experiments, the oats variety Sławko was selected as the most appropriate for brewing purposes. This variety was characterized by a high value of grain evenness and 1000 corn weight, and relatively low fat content.
The most favorable scheme for oats malting was developed based on the temperature, the degree of grain soaking and germination time impact on the process. The parameters which determined the quality of the malts were: extract content, protein content in malt and wort, enzymatic activity, and the viscosity of the wort. Optimal conditions for oat malt obtaining were chosen as: the temperature 14°C , 4-hour steeping in water, 2 hours draining, 3-hour steeping in water and 120 hours of germination. However, the resultant malts did not conform requirements for standard barley malt designed for beer production.
The attempts were made to improve the quality parameters of oat malt by obtaining so-called sour malts. The starter cultures of lactic acid bacteria were applied at the stage of grain steeping. After the initial selection, Lactobacillus delbrueckii ssp. delbrueckii 20074 was chosen as the best strain for the sour malt production. The application of starter culture to steeping water had a positive impact on the microbiological condition of the malt, wort extract content as well as the malt enzymatic activity.
For oat malts the most favorable conditions of mashing stage, which is the most important process for the beer production, were designed. Mashing process determines the extract and fermentable sugars content of the wort, which define the course of the fermentation. The specific rest temperatures were introduced. The rest temperature at 45°C was determined as the most advantageous for a high content of nitrogen compounds, low viscosity and the highest oat β-glucanase activity. Maltose rest temperature at 62°C resulted in the increase of the extract content, including fermentable extract, as well as in further reduction of the wort viscosity. Introduction of saccharification rest at 73° allowed to obtain a wort with the highest extract content and the shortest starch saccharification time, which resulted from the highest oat α -amylase activity under these conditions.
The use of enzyme preparations of β-glucanase (Filtrase NL) and α-amylase (Mycolase LV) during mashing allowed to increase the wort extract content, including the fermentable extract, as well as the nitrogen compounds, and also to raise the yield of the wort. Furthermore, the addition of enzymes allowed to reduce the concentration of β-glucans in wort, its viscosity and turbidity, to reduce the saccharification time and lighten the wortcolour.
The resultant oat beers were characterized by a low attenuation limit and low alcohol content. The character of the received beverages, including their flavour profile, was dependent mainly on the fermentation type. The type of the used raw material affected the parameters of beer to a lesser extent.
The received beverages contained health promoting components. It was found that the oat beers were the source of polyphenolic compounds and β-glucans. In addition, the blending of beers with fruit juices had a positive impact on the sensory quality of beverages and their antioxidant activity. The blend of bottom-fermented oat beer with apple juice, compiled in a volume ratio of 1:1, was indicated as the most attractive one.
Beverages obtained in this work were checked in respect to the safety for people with celiac disease. The much lower immunoreactivity for oats in comparison to barley and wheat flour was determined. The immune response was effectively reduced in the course of beer production process, during which most of the protein fractions were removed. The mixing of beers with fruit juices allowed further immunoreactivity reduction. The residual immune reaction in the final products might be caused by the protein fraction with a molecular weight of 38-40 kDa .
The result of the research is the design of technological process of low-alcohol oat beverages production, that can be new safe products in the diet of people suffering from celiac disease.