Polyphenols are the most important phytochemicals in our diets and have received great attention due to their broad benefits for human health by suppressing oxidative stress and playing a protective role in preventing different pathologies such as cardiovascular disease, cancer, diabetes, and obesity. The stability of polyphenols depends on their environments of processing and storage, such as pH and temperature. A wide range of technologies has been developed to stabilize polyphenols during processing. This review will provide an overview of the stability of polyphenols in relation to their structure, the factors impacting the stability of polyphenols, the new products deriving from unstable polyphenols, and the effect of a series of technologies for the stabilization of polyphenols, such as chemical modification, nanotechnology, lyophilization, encapsulation, cold plasma treatment, polyphenol–protein interaction, and emulsion as a means of improving stability. Finally, the effects of cooking and storage on the stability of polyphenols were discussed.

The protein extraction from the blue-green microalgae Spirulina platensis was carried out using ultrasound-assisted extraction and response surface methodology (RSM) was used to optimise extraction conditions. Extraction yield, total phenolic content, antioxidant activity and in vitro protein digestibility of protein extracts were determined. A three factors Box-Behnken design (BBD) of experiments was employed at pH values of 7, 8 and 9; temperatures of 25, 35, and 45°C; and for durations of 60, 90 and 120 minutes. Based on the RSM analysis, optimum extraction conditions (temperature 45°C, pH 7.46 and time 120 min) were obtained for extraction yield (29.05%), total phenolic content (3.52 mg caffeic acid equivalent/g dw), antioxidant activity (11.32 mg Trolox equivalent/g dw) and in vitro protein digestibility (99.36%). We report the first evaluation of the in vitro protein digestibility of Spirulina platensis and find it to be over 90%. This value is higher than the in vitro protein digestibility values of proteins obtained from other algae and plant species, and, in particular, is greater than that of commercial soybean protein isolate.

In the present study, optimum extraction conditions of proteins from Spirulina platensis were determined by using response surface methodology. Box-Behnken design of experiments was performed to investigate the effects of temperature (25, 35, 45°C), pH (7, 8, 9) and time (60, 90, 120 min) on water absorption capacity (WAC), oil absorption capacity (OAC), emulsifying activity (EA), emulsifying stability (ES), foaming capacity (FC) and foaming stability (FS) of the protein concentrates (PC). WAC of the PC varied with time while OAC changed with temperature and pH. The PC had high values of OAC (10.22 g of oil/g of protein) and WAC (5.12 g of water/g of protein) under extraction conditions of pH of 8 temperature of 45°C and time of 60 min. On the contrary, there were no significant changes in emulsifying properties of PC under different extraction conditions (p [ 0.05), while foaming stability of the PC varied with the interactive effect of temperature and time. The optimum extraction conditions were 43.87°C for temperature, 7.16 for pH and 60 min for time. Under these conditions, WAC, OAC, FC, FS, EA and ES values were obtained as 4.41 g of water/g, 10.13 g of oil/g, 300%, 83.94%, 42.99% and 92.50%, respectively. The results obtained through this investigation indicated that protein concentrates from Spirulina platensis have higher functional properties than other algae. Therefore, Spirulina platensis proteins can be thought as an inexpensive source of protein for food industry due to its extraordinary functionality.

This study aimed to investigate the effect of different drying methods on the drying kinetic, total bioactive content, in-vitro bioaccessibility of bioactive compounds, and color and microstructural properties of pomegranate arils. Drying methods significantly affected all selected parameters of dried pomegranate arils (P<0.05). Freeze-drying (FD) showed higher bioactive compounds, lower shrinkage, and better color quality than those of other samples. Ultrasound-assisted vacuum drying (UAVD) showed lower drying times, lower shrinkage, and higher bioactive compounds than vacuum drying (VD) and hot air drying (HAD). The ABTS, CUPRAC, and DPPH results were 34.53-63.71 μmol TE/g, 29.70-61.60 μmol TE/g and 64.82-93.69% DPPH radical scavenging activity, respectively. Also, the highest values of antioxidant capacity for all methods were obtained from the samples dried with FD followed by UAVD, VD, and HAD. The recovery of TPC in dried and fresh samples changed from 2.58% (fresh pomegranate) to 10.32% (vacuum-dried pomegranate). The recovery of TPC for freeze-dried samples (2.62%) was closest to the fresh ones and VD showed the highest TPC recovery. This study suggested that UAVD and VD should be used as alternative methods to HAD due to higher bioactive compounds retention, better color and surface quality, and higher recovery of bioactive compounds.

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Olive-mill wastewater (OMW), a by-product with high biological value and rich in phenolic compounds, is converted into spray-dried powders by using baker’s yeast cells (YCs) as carrier material. The encapsulation...

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