Abstract
Protein digestibility, secondary protein structure components, sugars, and phenolic compounds were analysed to investigate the effect of fermentation on the quality, structure, digestibility, and nonnutritive contents of lentil (Lens culinaris) proteins (LPs). Fermentation was carried out using water kefir seed. The initial pH of the unfermented LPs (6.8) decreased to pH 3.4 at the end of the fermentation on day 5. Protein digestibility increased from 76.4 to 84.1% over the 5 days of fermentation. Total phenolic content increased from 443.4 to 792.6 mg of GAE/100 g after 2 days of fermentation, with the sums of the detected phenolic compounds from HPLC analysis reaching almost 500 mg/100 g. The predominant phenolic compounds detected in fermented LPs include chlorogenic and epicatechin, while traces of rutin, ferulic acid, and sinapic acid were observed. Fermentation played a major role in the changes of the components in the secondary protein structure, especially the percentage of α -helices and random coils. In addition, the reduction in α -helix: β -sheet ratio with the increase in protein digestibility was related to the prolongation of the fermentation time. The model used in this research could be a robust tool for improving protein quality, protein degradation, and nonnutritive nutrients using water kefir seed fermentation.
Highlights
Research interest in establishing a clear alternative to the use of plant proteins has increased in recent years
Lentil seeds (Lens culinaris) and kefir seeds were purchased from iHerb (California, USA). e samples were transported to the laboratory inside an insulated box and kept at 4°C until use
After 1 h, a UV-Vis spectrophotometer (Shimadzu, UV-3600, Kyoto, Japan) was used to Fermentation was performed for 5 days at 25 °C 5% Water kefir seed (WKS) (v/v) solution was prepared with 1 g of lentil proteins (LPs) (w/v) in a 250 mL conical flask containing 95% (v/v) distilled water
Summary
Research interest in establishing a clear alternative to the use of plant proteins has increased in recent years. Lentil seeds are high in fibre content and low in fat, making them an attractive alternative source of protein [2]. Fermentation can be used to increase the digestibility of plant protein by decreasing the contents of nonnutritive compounds, e.g., phenolics, by promoting cross-linking between proteins, and the synthesis of microbial proteases, which could lead to minute breakdown and release of some of the proteins from the matrix [6,7,8]. E main purpose of this research is to investigate the effect of WKS on the digestibility, protein quality, and certain nonnutritive components of LPs. LPs are considered to be a strong alternative to soy protein because they are not genetically engineered and do not cause allergic problems. Is study is the first to investigate the effect of WKS on the quality, structure, digestion, and nonnutritive contents of LPs Information on the quality, structure, and nonnutritive contents of LPs is very limited. is study is the first to investigate the effect of WKS on the quality, structure, digestion, and nonnutritive contents of LPs
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