Abstract
Two multi-functional powders, in terms of anthocyanins from black rice (Oryza sativa L.) and lactic acid bacteria (Lactobacillus paracasei, L. casei 431®) were obtained through co-microencapsulation into a biopolymer matrix composed of milk proteins and inulin. Two extracts were obtained using black rice flour as a raw material and hot water and ethanol as solvents. Both powders (called P1 for aqueous extract and P2 for ethanolic extract) proved to be rich sources of valuable bioactives, with microencapsulation efficiency up to 80%, both for anthocyanins and lactic acid bacteria. A higher content of anthocyanins was found in P1, of 102.91 ± 1.83 mg cyanindin-3-O-glucoside (C3G)/g dry weight (DW) when compared with only 27.60 ± 17.36 mg C3G/g DW in P2. The morphological analysis revealed the presence of large, thin, and fragile structures, with different sizes. A different pattern of gastric digestion was observed, with a highly protective effect of the matrix in P1 and a maximum decrease in anthocyanins of approximatively 44% in P2. In intestinal juice, the anthocyanins decreased significantly in P2, reaching a maximum of 97% at the end of digestion; whereas in P1, more than 45% from the initial anthocyanins content remained in the microparticles. Overall, the short-term storage stability test revealed a release of bioactive from P2 and a decrease in P1. The viable cells of lactic acid bacteria after 21 days of storage reached 7 log colony forming units (CFU)/g DW.
Highlights
IntroductionVarious scientific studies have shown that black rice is a well-balanced food due to its remarkable nutritional properties [2], such as fibers, anthocyanins, vitamins B (thiamine, niacin) and E, iron, magnesium, and phosphorus [2]
A slow release of total anthocyanins content (TAC) and total polyphenolic content (TPC) from P2 may be observed starting with day 7, reaching a maximum of approximatively 5% for anthocyanins and 9% for polyphenols after 21 days of storage
Two microencapsulated powders containing biologically active compounds from black rice extracts and lactic acid bacteria were obtained in this study, from the perspective to develop products with applicability in different industries, which successfully meet the requests to be used as functional ingredients
Summary
Various scientific studies have shown that black rice is a well-balanced food due to its remarkable nutritional properties [2], such as fibers, anthocyanins, vitamins B (thiamine, niacin) and E, iron, magnesium, and phosphorus [2]. The black color is given by the high concentrations in anthocyanins, located in the pericarp and aleuronic layer of the rice [3]. The anthocyanin content of black rice is about 26.3%, with cyanidin-3-O-glucoside and peonidin-3-O-glucoside representing more than 90% of the total concentration [4]. The high content of biologically active compounds provides several beneficial properties. The pigmented rice contains compounds with antioxidant activity, such as flavones, proanthocyanidins and phenolic acids, contribute to black rice healthy biological profile [6,7]. It is known that anthocyanins are a class of flavonoids, highly reactive [7], and their stability depends largely on several environmental and chemical factors such as pH, metal ions, light exposure and UV, temperature, oxygen, and enzymatic
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