Abstract
The aqueous anthocyanin-rich extract derived from black rice (Oryza sativa L.) was encapsulated by freeze drying using milk proteins and peptides as coating materials. The molecular modelling approach indicated that all major casein fractions and whey proteins were able to bind at least one anthocyanin molecule. The hydrophobic interactions and hydrogen bonding across the interfaces appeared to be mainly responsible for the stabilizations of the complexes formed between the coating material and bioactive compounds. Two dark purple colored powders, differentiated by the ratio of the encapsulation materials used, rich in phytochemicals were obtained, with an encapsulation efficiency of up to 99%. The powders were tested for antioxidant activity, cytocompatibility, and thermal stability. The morphological structure of the powders highlighted the presence of encapsulated anthocyanins. Both powders showed a remarkable antioxidant activity of about 46 mM Trolox/g D.W., and cytocompatibility on the L929 fibroblast culture. At certain concentrations, both powders stimulated cell proliferation. The powders showed a good thermal stability between 75 and 100 °C for 15 min. The powders were tested in a food model system and checked for stability of phytochemicals during storage. The added value of the powders was demonstrated throughout the antioxidant activity, which remained unchanged during storage.
Highlights
Rice (Oryza sativa L.), as one of the most important staple crops, provides energy for almost half of the world’s population [1]
Whey protein isolate, whey protein hydrolysates, and casein were used for encapsulation of the anthocyanin-rich extract from black rice by freeze-drying, yielding high encapsulation efficiencies of almost 99%
Single molecule level investigations indicated that the complexes formed between the main milk proteins and anthocyanins from black rice are stable from a thermodynamic point of view
Summary
Rice (Oryza sativa L.), as one of the most important staple crops, provides energy for almost half of the world’s population [1]. Most of the phytochemicals are present in the bran layer and embryo fraction [2]. Whole rice grains are hypothesized to contribute positively to human health due to their polyphenols, minerals, fiber, vitamins, and other phytochemicals [3,4], which may influence biological functions individually or synergistically [1]. The pigmentation of black rice samples is due to the accumulation of anthocyanins and proanthocyanidins in rice bran. Two major anthocyanins found in black rice are cyanidin-3-O-glucoside (C3G) and peonidin-3-O-glucoside (P3G) [5]. There are several reports suggesting that the consumption of pigmented rice can promote a decrease of oxidative stress, prevent inflammation, and reduce the risk of developing chronic diseases, like cardiovascular
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