The choice of probiotics affects the rheological, structural, and sensory attributes of lupin-oat-based yoghurt

Abstract

Plant-based yoghurt (PBY) presents an alternative for vegetarians, flexitarians, and individuals with dairy allergies. However, how the bacterial (culture) variations can impact the properties are not yet well investigated. This study aims to investigate the physicochemical attributes, encompassing texture, rheological properties, microstructure, and sensory characteristics, of yoghurt formulated with a lupin-oat base as affected by the addition of commercial probiotics including Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus rhamnosus, L. casei 431 (Lactobacillus paracasei), Lactobacillus plantarum, BB12 (Bifidobacterium sps) during storage at 4 °C for 28-day. Significantly, lupin-oat yoghurt fermented with a combination of Lactobacillus plantarum, and Bifidobacterium species exhibited rapid metabolic activity, leading to a notable reduction in fermentation time compared to other probiotic strains. Furthermore, this combination conferred similar water-holding capacity, firmness, and consistency with dairy yoghurt (control). Different probiotic strains induced variations in particle size and led to shear-thinning behaviour across all yoghurt samples. Over the refrigerated storage, a decline in apparent viscosity was observed and lupin-oat yoghurt exhibited greater rigidity compared to dairy yoghurt. Changes in the yoghurt microstructure during storage, notably the presence of increased serum pores were associated with its functional attributes. Confocal and scanning electron microscopy revealed distinctive microstructural features in yoghurt fermented with Lactobacillus plantarum and Bifidobacterium species compared to other probiotic combinations. Notably, this combination garnered higher sensory ratings for appearance, taste, flavour, texture, and overall acceptability, positioning it as a suitable dairy yoghurt alternative. These findings provide insights into enhancing the structural and sensory attributes of lupin-oat-based yoghurt.