Protein quality of oat-pea-based yoghurt alternatives produced using pulsed electric field treatment and probiotic starter cultures

Abstract

Protein quality remains a key nutritional challenge in plant-based yoghurt alternatives (PBYA), often limited by suboptimal amino acid profiles, antinutritional factors, and low protein digestibility. Therefore, this study aimed to evaluate protein quality, assessed via the in vitro protein digestibility corrected amino acid score (ivPDCAAS), of an oat-pea blended PBYA alongside textural properties and acidification behaviour. Following pasteurisation using pulsed electric fields technology, samples were subjected to a yoghurt fermentation (8 h at 35 °C) with selected probiotic organisms, Lactiplantibacillus plantarum 299v (Lp299v) and Lacticaseibacillus paracasei 431, alongside a conventional yoghurt culture, YF-L812 (Yo-flex), and a bioprotective starter culture, Bioprox RP80. Results revealed that a nutritionally complete amino acid profile, meeting FAO requirements, could be achieved by combining oat and pea materials. PEF treatments at 10 kV cm⁻¹ and 213 kJ L⁻¹ with preheating (45 °C, 22 s) followed by lactic acid fermentation achieved an overall mild improvement in protein digestibility by up to 17%, linked to a partial degradation of antinutritional factors (phytic acid by 18% and trypsin inhibitor by 17%). This increased the nutritonal protein quality of the PBYA by up to 14%, dependant on the amino acid metabolism of the selected probiotic starter cultures, which included a slight (11–17%) reduction in sulphur amino acids (cysteine, methyonine). Additionly, the probiotic Lp299v achieved a faster acidification and firmer yoghurt texture compared to a conventional yoghurt culture (Yo-flex), while the co-culture Bioprox RP80, containing Lp. plantarum and Lc. rhamnosus, proved equally suitable. These findings underscore the potential of alternative starter cultures, utilising probiotic species such as Lp. plantarum with a versatile metabolic profile to achieve an efficient acidification and suitable textural properties of PBYA without adversely affecting protein quality indices. Moreover, the integration of PEF as an alternative pasteurisation method benefits the preparation of PBYA by minimising the degradation of amino acids while partially reducing antinutritients. The applied technologies are scalable for industrial use. As such, this research supports future innovations in commercial PBYA applications by providing key insights into the influence of PEF and fermentation on protein nutritional quality.