Cellulase-Xylanase-Treated Guava Purée by-Products as Prebiotics Ingredients in Yogurt

Fruit processing by-products may be re-utilized as prebiotic ingredients to minimize the environmental impact of solid wastes generated from food industries. This study investigated the effects of enzymatic-induced hydrolysis on two types of guava purée by-products, particularly the prebiotic activity after its inclusion in yogurt-making. Commercial cellulase and xylanase were applied together or separately on refiner (the seed-rich fraction), and decanter (the pulp-rich fraction); labelled as 150 XY (xylanase); 150 CE (cellulase), 150 CX (combined cellulase-xylanase), and CT (control, untreated). The hydrolysis extents followed the order of 150 XY < 150 CE < 150CX. The ethanolic extracts (EEC) of the treated samples were analyzed on selected sugar content and the prebiotic activity score. Rhamnose and xylose were the main sugar constituents in both refiner and decanter. A two to four-fold increments of prebiotic activity score were observed on EEC of combined cellulase and xylanase treated decanter and refiner. Incorporating the combined enzymatically treated whole guava by-products into UHT fresh milk containing a yogurt starter culture significantly increased the log CFU/mL up to 77.6%, enhanced hardness, stickiness, and adhesiveness ranging from 22.2 to 86.4%, and decreased pH values. Combined cellulase-xylanase treatment can convert guava purée by-products into potential prebiotic sources for food applications.