Abstract
SUMMARYThe aim of this work is to obtain new food products enriched with bioactive compounds from concentrated grape juice microencapsulated by freeze drying using a whey protein isolate-chitosan system. The obtained powder showed an encapsulation efficiency of (86.1±4.0) %, with an anthocyanin mass fraction (expressed as cyanidin-3-O-glucoside equivalent) of (1.4±0.2) mg/g, while the total polyphenolic (expressed as gallic acid equivalents) and flavonoid (expressed as catechin equivalents) mass fractions were (3.3±0.6) and (1.6±0.5) mg/g, respectively. The confocal laser microscopy revealed the presence of the flavonoid pigments wrapped inside the matrix, whereas the anthocyanins were grouped into large and compact clusters. The microencapsulated powder was used for jelly formulation. The new food formulations have a satisfactory anthocyanin mass fraction ranging from (0.03±0.01) to (0.12±0.02) mg/g, while no significant differences were observed in flavonoid content. All the value-added jelly showed appreciable antioxidant activity. The in vitro digestibility results confirm a slow release of anthocyanins from the food matrices during simulated gastric digestion and a significant release of the bioactive compounds into the gut. The addition of microencapsulated powder caused a significant decrease in firmness, cohesiveness and springiness, leading to the destabilization of the gel structure, while reducing the attraction forces between the matrix components. The sensorial analysis indicated that the panellists preferred the sample with grape juice the most.
Highlights
New alternatives to synthetic colourants in food applications are increasing due to the consumer demands for natural pigments
Encapsulation efficiency and phytochemical parameters of microencapsulated powder After microencapsulation of concentrated juice, the resulting powder was analyzed with respect to EE, total anthocyanin (TAC), TPC, total flavonoid content (TFC) and antioxidant activity
The phytochemicals from concentrated red grape juice were successfully microencapsulated in a whey protein isolate-chitosan system, with encapsulation efficiency of anthocyanins of 86 %
Summary
New alternatives to synthetic colourants in food applications are increasing due to the consumer demands for natural pigments. The grapes are suitable source of bioactive compounds and pigments. Grapes are consumed in different states, such as fresh, processed in the winemaking, jam, jelly, juice, vinegar, extract and oil production. The use of grape pomace for agricultural purposes is limited due to its high content of polyphenols including flavonoids, phenolic acids, stilbenes and tannins that are potentially toxic to the soil microbiota [3]. Meini et al [4] suggest that, nowadays, the main potential uses of grape pomace include the extraction of tartaric acid, ethanol production, distillation processes, as fertilizer and as an additive in animal feed. The applicability of grape pomace is limited due to the fact that at high mass fractions of phenolics the germination is inhibited, whereas the presence of polymeric polyphenols reduces the digestibility
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