The addition of Andean lupin (Lupinus mutabilis) protein concentrate enhances the nutritive value and the antioxidant activity of yoghurt

Abstract

Introduction: Andean lupin seeds are under-exploited sources of nutrients and bioactive compounds. Materials and methods: seeds were debittered to remove toxic alkaloids, partially defatted with 70% ethanol, dried at 60°C and milled. The defatted flour was suspended in water adjusted at pH 7 with 1N NaOH. The protein extract was filtered and spray-dried. Enriched yoghurts were obtained with the addition of lupin protein concentrate at 0.5, 1 and 1.5%. The chemical and fatty acid composition, the contents of polyphenols and flavonoids as well as the antioxidant activity were determined. The microbial quality and physicochemical properties (pH values, lactic acid content and percentage of syneresis) were evaluated in yoghurts during 28 days of storage. Results: Andean lupin concentrate showed high protein and carbohydrate contents (69% and 20%), unsaturated fatty acids (77%) mainly oleic, linoleic and α-linolenic acids as well as low atherogenic and thrombogenic indexes (0.07 and 0.44). The addition of the lupin protein concentrate at 1.5% into yoghurts increased the protein content. Enriched yoghurts showed higher unsaturated fatty acids, total polyphenol and flavonoid contents as well as lower atherogenic and thrombogenic indexes compared to the control. The lupin protein concentrate increased the ABTS radical scavenging activity, the ferric reducing power and the total antioxidant activity in yoghurts. Enriched and control yoghurts showed similar lactic acid bacterial counts. The counts for total and thermotolerant coliforms were under three MPN/mL and yeast and molds under 10 CFU/ mL. The pH values in enriched products were higher at days 1 and 7 of storage (4.82 and 4.95) compared to the control sample (4.72 and 4.85). The lactic acid content increased in all formulations at day 21. Enriched yoghurts showed lower syneresis than the control. Conclusions: Yoghurts enriched with lupin protein concentrate could represent nutritive and functional alternatives to prevent chronic diseases when consuming in a healthy diet.