Ultrasound technology for the modification of red raspberry by-products: effects on techno-functional and nutraceutical characteristics.

Abstract

Raspberries are one of the fruits with the most economical relevance for the state of Jalisco in Mexico. However, it has been estimated that around 37% of the total production does not comply with the minimum quality standards to be eligible for commercialization or exportation. These by-products may enhance the generation of novel ingredients with unique techno-functional properties and nutraceutical characteristics. Furthermore, consumer’s demand for healthier foods have increased in the last years. It represents an opportunity to incorporate ingredients, such as fruit and vegetables’ powders (FVP) and phenolic compounds into food formulations. Ultrasound (US) processing is increasingly used for the modification of dietary fiber (DF) characteristics and phenolic composition of fruit and vegetable matrixes. The aim of this investigation was to evaluate the effect of different ultrasonic treatments on the dietary fiber content, proximate, and phenolic composition, techno-functional properties and antioxidant capacity of red raspberry by-products’ powder (RP). A three factorial Box-Behnken design including as variables the liquid and solid ratio (LS; 10:1, 20:1, 30:1 mL:g), processing time (20, 30, 40 min), and US-amplitude (50, 75, 100%) was conducted to study changes in total (TDF), high molecular soluble (SDFP) and insoluble (IDF) dietary fiber contents, water-/oil holding capacity (WHC/OHC), solubility (SOL), swelling capacity (SC), tap density (TP), hygroscopic properties, total phenolic (TPC) and anthocyanin (TAC) content and scavenging capacity in terms of DPPH and ABTS. Finally, this study evaluated the effect of RP as fat replacer on the textural and sensory characteristics on ice cream mixes. Results showed that all studied US conditions solubilized IDF and increased the SDF:IDF ratio. WHC and OHC increased, whereas TP decreased at almost all the US conditions employed. SOL and SC values did not show a unique behavior when compared to that of the non-US treated (N-UST) RP. Adsorption and desorption isotherms of RP showed a type III classification of BET and N-UST RP displayed higher equilibrium moisture content over all the aw values studied. The maximum recovery of phenolic compounds (4632.7 μg GAE/g db) was achieved using 100% US-amplitude, for 30 min with a LS ratio of 10:1 mL:g and the highest TAC (1883.9 μg CGE/g db) value was achieved by applying 75% US-amplitude, for 20 min at 20:1 mL:g LS ratio. No correlations were found between TPC, TAC and RP’s antioxidant activity. Ice cream supplemented with RP showed lower overrun values and greater melting resistance compared with control ice cream (without RP). Finally, addition of RP improved sensory characteristics of ice creams with the rating resembling to one of high-fat product.