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

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.

摘要：开菲尔（Kefir）是由醋酸菌、乳酸菌与酵母菌构成的复合菌群，可广泛应用于植物基质的生物转化，并可改善其生物活性特性。小扁豆是一类富含维生素、矿物质、复合碳水化合物及蛋白质的豆科作物，是发酵制备生物活性分子的优质基质。本研究以开菲尔为生物转化剂，结合实验设计方法，探讨了不同工艺变量对小扁豆提取物抗氧化性能的影响。研究结果表明，搅拌转速（rpm）与培养温度对产物抗氧化性能具有显著影响。其中，28℃的培养温度与75 rpm的搅拌转速为开菲尔发酵小扁豆、最大化其发酵产物抗氧化性能的最优条件。通过总抗氧化能力、FRAP法与DPPH自由基清除法测得的发酵产物最高抗氧化活性分别为每克样品4128.39、35.87与23.20 μmol Trolox当量（μmol TE g⁻¹）。此外，本研究发现发酵初始阶段（前6小时）即可对小扁豆提取物的抗氧化性能产生积极影响，与未发酵样品相比，发酵产物的抗氧化活性最高可提升270%。