Influence of Fermentation Vessels and Olive (Olea africana) Ash on Proximate Composition, Phytochemicals and Consumer Acceptability of Spontaneously Fermented Milk

In addition to its cultural significance, naturally flavored spontaneously fermented milk is linked to health and nutritional benefits. Traditionally, the milk is fermented in gourds, but considering their current scarcity, it is necessary to explore use of other fermentation vessels that could guarantee the continuation of these practices. This study investigated the effect of incorporation of Olea africana ash (OAA) in spontaneously fermented milk using different fermentation vessels, such as gourds (G) and polyethylene terephthalate (PET) plastic (P) vessels. Different concentrations of OAA were used; control 0.00% (GC0 and PC0), 0.05% (G05 and P05), 0.10% (G10 and P10), and 0.20% (G20 and P20). The proximate composition, mineral content, total phenolic and total flavonoid contents, antioxidant activity, physicochemical properties, microbial quality, and consumer acceptability of the spontaneously fermented milk were determined. The crude ash content and mineral composition increased significantly with addition of OAA in a dose-dependent manner. Specifically, macro elements calcium (106.14 – 130.04 mg/100g), potassium (201.93 – 250.26 mg/100g), sodium (36.83 – 42.55 mg/100g), magnesium (6.75 – 9.51 mg/100g), and phosphorus (123.61 – 138.86 mg/100g), and micro elements zinc (0.04 – 0.16 mg/100g), iron (0.08 – 0.60 mg/100g), and manganese (0.08 – 0.30 mg/100g). The OAA reduced the acidity of spontaneously fermented milk, but the pH and TTA were within the recommended standard range. Both gourds and OAA enhanced the viscosity, total phenolic, total flavonoid contents, and antioxidant activity. A strong positive relationship of antioxidants with both phenolics and flavonoids was observed from the Pearson’s correlation. The addition of OAA significantly inhibited the growth of yeast and molds in a dose-dependent manner. The freshly fermented milk samples up to 0.10% OAA in both vessels were generally rated as acceptable by consumers. This study provides scientific knowledge, empowers small-scale producers, and promote the nutritional value of foods through home-based production of traditional fermented milk. In conclusion, based on the nutritional, functional, and consumer acceptability, spontaneously fermented milk in both gourds and PET vessels containing 0.10% OAA produced the best results. Therefore, PET vessels could be considered for milk fermentation after further validation. Key words: Olea africana, milk, spontaneous fermentation, proximate, phytochemicals, consumer acceptability, fermentation vessel