Optimization of Shear Homogenization of Cactus Pear (Opuntia ficus-indica) Peel and Physicochemical Characterization for Vinegar Production

Abstract

Cactus pear (Opuntia ficus-indica) is widely cultivated in arid and semi-arid areas of Tigray, Ethiopia, where it plays an important role in food security and rural livelihoods. However, a large proportion of cactus pear fruit by-products, particularly peels, are discarded, resulting in environmental pollution and loss of potential value. This study aimed to optimize peel shear homogenization conditions for improved extraction of fermentable substrates and to evaluate the physicochemical characteristics of vinegar produced from cactus pear fruit peel. A non-thermal shear homogenization process was optimized using Response Surface Methodology (RSM) with a Central Composite Design, considering homogenization temperature, time, and frequency as independent variables. The effects of these variables on total soluble solids, titratable acidity, and vitamin C content of the peel juice were evaluated. The optimized peel juice was subjected to a two-stage fermentation process involving alcoholic fermentation using Saccharomyces cerevisiae followed by acetic fermentation using Acetobacter aceti to produce vinegar. The resulting vinegar was analyzed for yield and key physicochemical properties. The results demonstrated that shear homogenization significantly enhanced the extraction of sugars and organic acids, producing a suitable fermentation substrate for vinegar production. The optimized process conditions yielded vinegar with desirable acidity and quality attributes, meeting standard vinegar requirements. This study confirms that cactus pear fruit peel can be effectively valorized into value-added vinegar using optimized non-thermal homogenization and fermentation techniques. The findings contribute to sustainable food value chain development by reducing post-harvest waste, enhancing resource utilization, and providing an alternative income-generating opportunity for cactus pear producers in Tigray.