Preparation of pH-indicator films based on soy protein isolate/bromothymol blue and methyl red for monitoring fresh-cut apple freshness.

Intelligent pH-indicator films based on soy protein isolate (SPI) were prepared using pH-sensitive dyes (bromothymol blue and methyl red). The addition of mixed indicators imparts pH-indicator films with an appreciable microstructure, acceptable water resistance, and favorable optical properties. The incorporation of the mixed indicators did not lead to significant improvement in the mechanical properties of films due to weak ionic cross-linking by hydrogen bonding between the SPI macromolecules and low-molecular-weight indicators. Fourier-transform infrared spectroscopy indicated hydrogen bond-mediated intermolecular interactions, and scanning electron microscopy showed that BB/MR were well dispersed in the SPI film. The indicator addition hindered the sorption and passage of water molecules. The water vapor permeability, moisture sorption, moisture content, and total soluble matter were 4.32 to 6.12 ×10-12  g·cm/cm2 ·s·Pa, 36.70% to 73.33%, 25.28% to 44.11%, and 8.21% to 25.56%, respectively. Also, the addition of indicators reduced UV light transmittance with minimal effect on the transparency of the film. The presence of indicators enhanced the pH sensitivity, seen as a visible color reaction at different pHs (total color difference, ΔE > 5). When the pH-indicator film containing 8 ml/100 ml final film emulsions was used to monitor the fresh-cut apple freshness, a green color for fresh status was observed, which turned blue after 60 h. Collectively, our findings suggested that indicator-containing SPI films have the potential for monitoring the freshness of fruits. PRACTICAL APPLICATION: pH-indicator films can help consumers to identify the freshness of packaged food by a change in the color of the packaging material, which is easily visible to the unaided eye without the need for opening the packaging. This protects consumers' interests.

Physicochemical properties, antioxidant activities and protective effect against acute ethanol-induced hepatic injury in mice of foxtail millet (Setaria italica) bran oil.

This study was designed to investigate physicochemical characterization of the oil extracted from foxtail millet bran (FMBO), and the antioxidant and hepatoprotective effects against acute ethanol-induced hepatic injury in mice. GC-MS analysis revealed that unsaturated fatty acids (UFAs) account for 83.76% of the total fatty acids; in particular, the linoleic acid (C18:2) is the predominant polyunsaturated fatty acid (PUFA), and the compounds of squalene and six phytosterols (or phytostanols) were identified in unsaponifiable matter of FMBO. The antioxidant activity examination of FMBO in vitro showed highly ferric-reducing antioxidant power and scavenging effects against DPPH· and HO· radicals. Furthermore, the protective effect of FMBO against acute hepatic injuries induced by ethanol was verified in mice. In this, intragastric administration with different dosages of FMBO in mice ahead of acute ethanol administration could observably antagonize the ethanol-induced increases in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), and the hepatic malondialdehyde (MDA) levels, respectively, along with enhanced hepatic superoxide dismutase (SOD) levels relative to the control. Hepatic histological changes were also observed and confirmed that FMBO is capable of attenuating ethanol-induced hepatic injury.