EFFECT OF POLYPHENOL OXIDASE INACTIVATION ON THE TECHNO-FUNCTIONAL PROPERTIES OF SWEET POTATO PROTEIN EXTRACTS

Sweet potato production exceeds 100 million tons per year, with half of it being destined for starch extraction, generating underutilized and environmentally impactful protein residues (~1.5% w/w). However, sweet potato contains polyphenol oxidase (PPO), which can affect its techno-functional properties and limit its industrial application. Thus, this study aimed to evaluate the effect of enzymatic inactivation on the functional properties of sweet potato proteins, seeking to optimize their utilization as a sustainable protein source. The sweet potatoes were peeled and subjected to enzymatic inactivation by treatment AB, consisting of ascorbic acid (0.8 mM / 3 min) combined with blanching (50 °C / 3 min), and by treatment SM, using sodium metabisulfite (0.05 mM / 3 min). The protein extracts were concentrated by isoelectric precipitation (pH 4.1), resuspended at pH 7.0, and freeze-dried. The techno-functional properties were evaluated. The results showed that both treatments improved water absorption capacity, sample SM showed the highest value (1.00 g/g), followed by sample AB (0.45 g/g), compared to the control (0.16 g/g). Improving water absorption capacity is relevant for the development of several products, such as bakery products, where protein hydration directly affects dough handling and texture. Sample AB has the highest value of emulsion stability with a creaming index of 79.00% after 1 hour, while sample SM (51.2%) showed similar values to the control (52.0%). Enhanced stability suggests a potential application in emulsified systems such as sauces and beverages. In contrast, oil absorption capacity, foaming capacity, foaming stability, gelling capacity and emulsifying capacity were not significantly influenced by the treatments. These results reveal that it is possible to modulate the water absorption capacity and emulsion stability of the extracts based on the choice of enzyme inactivation pretreatment targeting specific applications, enabling the potential use of the sweet potato protein extracts in the food industry.