Polysaccharides from pineapple core as a canning by-product: Extraction optimization, chemical structure, antioxidant and functional properties.

Ultrasonic-assisted extraction (UAE) technique has been investigated to extract polysaccharides from pineapple core as a by-product using response surface methodology. A Box-Behnken design was employed to optimize the conditions for the maximum extraction yield of polysaccharides. The results demonstrated that the optimum extraction conditions were as follows: water/solid material ratio of 29.5 mL/g, extraction temperature of 66.3 °C and extraction time of 46.7 min. Under these conditions, the extraction yield of pineapple core polysaccharides (PCPs) was 16.7%. The structure of PCPs was analyzed by Fourier transform-infrared spectroscopy (FT-IR) analysis, X-ray diffractometry (XRD), SEM (scanning electron microscope) and gas chromatography-mass spectrometry (GC-MS). The results of thermogravimetric analysis indicated that the PCPs had a good thermal stability at temperatures below 250 °C. The extracted polysaccharides had a porous structure with rough surface. The extracted polysaccharides had strong scavenging activities on DPPH and hydroxyl radicals. Furthermore, they demonstrated interesting water-holding and fat-binding capacities (3.11 and 4.25 g/g, respectively). The results revealed that polysaccharides displayed good emulsifying and foaming properties. Overall, the findings suggest that PCPs are a promising source of antioxidants and may have potential applications in functional food industries.

Application of Ultrasound-Ultrafiltration-Assisted alkaline isoelectric precipitation (UUAAIP) technique for producing alfalfa protein isolate for human consumption: Optimization, comparison, physicochemical, and functional properties.

A new Ultrasound-Ultrafiltration-Assisted Alkaline Isoelectric Precipitation (UUAAIP) technique was employed for producing alfalfa protein isolate from alfalfa leaves. A five-factor-three-level Box-Behnken Design (BBD) was used to optimize the UUAAIP process for maximizing both extraction yield and protein content simultaneously. The optimum conditions were as follows: solvent/solid material ratio of 43.3 mL/g, pH of 10.1, extraction temperature of 42.5 °C, extraction time of 102 min, and flow rate of 9.7 L/h. Under these conditions, the maximum predicted extraction yield and protein content were 14.5 g/100 g and 91.1 g/100 g, respectively. UUAAIP technique improved the average molecular weight and color of the isolate. Moreover, it was efficient in removing the saponins and phenolic compounds as anti-nutritional factors compared to heat-coagulation extraction (HCE) and alkaline isoelectric precipitation extraction (AIPE). The protein isolate extracted by UUAAIP had greater solubility, water-holding and oil-binding capacities but lower emulsifying and foaming properties than those extracted by HCE and AIPE.