Abstract
Flaxseed oil cake (FOC) was evaluated as a potential substrate for the production of a novel kefir-like fermented beverage. Three variants containing 5%, 10%, and 15% (w/w) of FOC were inoculated with kefir grains and incubated at 25 °C for 24 h. After processing, beverages were stored in refrigerated conditions (6 °C) for 21 days. Changes in microbial population, pH, acidity, levels of proteins, polyphenolics, flavonoids, ascorbic acid, and reducing sugars were estimated. Additionally, viscosity, firmness, color, and antioxidant properties were determined. Results showed that lactic acid bacteria as well as yeast were capable of growing well in the FOC without any supplementation. During refrigerated storage, the viability of the microorganisms was over the recommended minimum level for kefir products. As a result of fermentation, the beverages showed excellent antioxidant activity. Because of the functional characteristics conferred to the FOC beverages, the use of kefir grains showed adequate potential for the industrial application. Therefore, this beverage could be used as a new, non-dairy vehicle for beneficial microflora consumption, especially by vegans and lactose-intolerant consumers.
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Key Points
Oil cakes/oil meals are the by-products obtained after oil extraction from the seeds. There are two types of oil cakes: edible and non-edible. Edible oil cakes are characterized by high nutritional value, i.e., their protein content ranges from 15% to 50%. Flaxseed oil cake is a cheap by-product of flaxseed (Linum usitatissimum L.) oil pressing and is of a source of many bioactive substances such as proteins, fiber, and lignans. There have been no reports about utilization of flaxseed oil cake obtained via cold press technique to produce fermented kefir like-beverages. Thus, the aim of the presented study is to produce a beverage based on various concentrations of flaxseed oil cake fermented by kefir grains and an evaluation of its bioactivity, microbiological, and physiochemical properties during refrigerated storage for 21 days. As kefir grains possess healthy features, the study showed the way for their future employment in the fermentation industry, leading to products with high added value that are ready to be consumed. The microorganisms survivability and antioxidant activity over a 21-days storage period in refrigerated conditions made the beverages of high added value which can be characterized as functional foods. Another key point to be noted is that the bioprocess utilizing oil cakes is attractive because of relatively cheaper availability of the oil cakes throughout the year, making it even more favorable when economic issues are considered.