African Walnut (Plukenetia conophora)-Fortified Yoghurt: Fatty Acids, Oxidative Stability, Physicochemical Properties, and Sensory Attributes During Chill Storage

Abstract

This study investigated the impact of fortifying yoghurt with African walnut (Plukenetia conophora) on its fatty acid (FA) profile, physicochemical properties, microbial profile, oxidative stability, and sensory attributes. Yoghurts made from cow milk were fortified with 0%, 1%, or 2% African walnut (AW) paste and evaluated over 14 days of refrigerated storage. AW fortification increased crude fat, phytochemical constituents, and concentrations of C18:1n − 9 and C18:3n − 3 while reducing C14:0, C16:0, and C18:0 levels (p < 0.05). FA composition remained stable in AW-fortified yoghurts, but the control showed an increase in saturated FAs and a reduction in C18:1n − 9 and C18:3n − 3 over time. Although color, Lactobacillus count, and lipid oxidation were unaffected, carbonyl content and syneresis decreased with AW fortification. Sensory results showed that younger assessors (19–39 years) preferred the control yoghurt, whereas older assessors (40–52 years) favored the 2% AW-enriched yoghurt for its taste, texture, and overall quality. Principal component analysis revealed that AW fortification significantly influenced the quality attributes of yoghurt during chilled storage, with AW-2 samples showing improved compositional integrity and reduced quality deterioration over time. AW fortification improved yoghurt's nutritional value and oxidative stability, making it a promising functional food, especially for older consumers.

Practical Applications: Yoghurts are typically high in saturated fatty acids (SFAs) but low in n − 3 fatty acids. A high intake of SFAs can pose health risks, highlighting the need to increase the n − 3 fatty acid content in yoghurt. Fortification with African walnut boosts C18:3n − 3 levels and reduces SFAs, making the yoghurt a healthier choice. In addition, the reduced carbonyl content and syneresis indicate an extended shelf life and improved quality. The age-related sensory preferences observed in this study suggest that African walnut–enriched yoghurt may be more appealing to older consumers, who value overall quality. This fortification could lead to the development of functional foods tailored to different age groups, encouraging healthier eating habits. Processors can use this approach to create yoghurt products with enhanced health benefits, addressing consumer demand for nutritious and functional dairy options.