Effects of Vacuum Impregnation with Calcium Ascorbate and Disodium

30 This study aimed to improve the shelf life of Chinese red bayberries using vacuum impregnation. 31 Vacuum pressure of 5 kPa for 15 min, atmospheric pressure for 10 min, an impregnation temperature of 32 20 °C, alone or in combination with isotonic sucrose solution, 1% food-grade disodium stannous citrate 33 (DSC), and 2% food-grade calcium ascorbate were used for vacuum impregnation. Quality parameters, 34 including firmness, weight loss, decay rate, microbial counts, and polyphenol oxidase (PPO) and 35 peroxidase (POD) activities, of red bayberries were studied at 2 °C for 10 days. The monosaccharide 36 components, chemical structures, and nanostructure properties of chelate-soluble pectin (CSP) were 37 further studied using high performance liquid chromatography, Fourier transform infrared 38 spectroscopy, and atomic force microscopy (AFM). The results indicated that vacuum impregnation 39 with calcium ascorbate alone or calcium ascorbate combined with DSC, showed significant effects on 40 inhibiting the decrease of firmness (4-10 d), the increase of weight loss (2-10 d), decay rate (4-10 d) 41 and microbial growth (2-10 d). In addition, vacuum impregnation with single calcium ascorbate or 42 DSC or their combination significantly inhibited the increase of colour difference from day 6 to day 10 43 during storage, which was better than atmospheric impregnation. Furthermore, vacuum impregnation 44 with DSC and calcium ascorbate had the best effect on sensory attributes. The nanostructure analysis 45 by AFM showed CSP of large width and length when calcium ascorbate was impregnated, suggesting 46 that vacuum impregnated with 2% calcium ascorbate inhibited the degradation and dissociation of CSP, 47 although these fruits showed more branching of rhamnogalacturonan and a small change in chemical 48 structure. 49 50