Effect of soaking with Lactiplantibacillus plantarum LB-1 and heat treatment on the nutritional composition and microstructure of wholegrain oat (Avena sativa L.)

The impact of soaking and thermal processing (boiling) on the chemical composition and microstructure of kilned wholegrain oats with their hull remains poorly characterised, despite its relevance for nutritional enhancement. This study examined the effects of soaking, both with and without Lactiplantibacillus plantarum LB-1 (LAB), followed by heat treatment on oat kernel composition, dietary fibre fractions, molecular weight, phytic acid, and total phenolics. Soaking and boiling induced a decline in resistant starch and an increase in nonresistant starch, suggesting partial gelatinisation and enzymatic breakdown. Phytic acid, an antinutrient that limits mineral absorption, decreased by 32-37% after soaking and cooking compared to its initial value in the raw material. The phenolic content decreased after pre-treatment, likely due to solubilisation and heat-related degradation. Microstructural analysis showed cell wall loosening, starch granule swelling, and nutrient dispersion, particularly in LAB-treated samples. During the soaking step the pH dropped to 4-5 over 12 h with LAB compared to pH 6 in water-soaked oats. These structural and chemical modifications indicate that soaking, notably when combined with LAB, could improve starch accessibility and reduce antinutritional factors. The findings offer mechanistic insight into how pre-treatment can improve the nutritional quality and functionality of oats.