Kefir fermentation as a bioprocess to improve lentils antioxidant properties: is it worthwhile?

Iuri Magalhães De Alencar Oliveira,Ruann Janser Soares De Castro

doi:10.1590/1981-6723.12019

Iuri Magalhães De Alencar Oliveira, Ruann Janser Soares De Castro

Open Access

https://doi.org/10.1590/1981-6723.12019

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Abstract

Abstract Kefir, a consortium of acetic and lactic bacteria and yeasts, is versatile for biotransformation of vegetable substrates and may improve their bioactive properties. Lentil is a legume rich in vitamins, minerals, complex carbohydrates and proteins, making it an excellent substrate for fermentation and obtaining bioactive molecules. We report the effect of different process variables on antioxidant properties of lentil extracts obtained using kefir as a biotransformation agent and experimental design. The results showed that the factors agitation (rpm) and incubation temperature exerted significant effects. Incubation temperature of 28 °C and agitation of 75 rpm were the most suitable conditions for kefir fermentation and maximizing the antioxidant properties of the fermented lentils. The highest antioxidant activities for fermented products were 4128.39, 35.87 and 23.20 μmol of Trolox equivalents per gram of sample (μmoL TE g-1) measured by Total Antioxidant Capacity, FRAP and DPPH-radical scavenging methods, respectively. Additionally, we detected that the initial fermentation times (in the first six hours) were enough to positively affect the antioxidant properties of the lentil extracts, reaching a percentage increase of up to 270% in the antioxidant activity of the fermented products in relation to those non-fermented samples.

Highlights

Kefir grains comprise the association of different groups of microorganisms including yeasts, acidic lactic and acetic bacteria in a matrix composed of polysaccharides and proteins (Gulitz et al, 2011; Amorim et al, 2019)
2.5 Effects of the cultivation parameters on antioxidant properties of lentil extracts We evaluated the effects of kefir grains culture parameters, including agitation and incubation temperature using a Central Composite Rotatable Design (CCRD) at different levels (Table 1)
The results obtained from CCRD for the different runs showed that the independent variables had interesting effects on the fermentation process, with great variation of the antioxidant activities according to each culture condition (Table 1)

Summary

Introduction

Kefir grains comprise the association of different groups of microorganisms including yeasts, acidic lactic and acetic bacteria in a matrix composed of polysaccharides and proteins (Gulitz et al, 2011; Amorim et al, 2019). Most scientific studies aim at obtaining fermented products of milk origin, kefir grains have shown great potential for application in the production of different functional beverages based on fruits and vegetables. This alternative route presents a very interesting appeal to offer new products to a growing market that includes vegan consumers, lactose intolerant and those allergic to dairy products (Fiorda et al, 2017). The presence of phytochemicals, such as phenolic acids, flavonoids and other related phenolic compounds can be pointed out as a notable characteristic of these grains, since these substances are strongly associated with some biological properties, such as antioxidant activity (Zhang et al, 2015; Fiorda et al, 2017)

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