Abstract: In order to control the softening of canned solid pack apples, the decompression pre-pumping-assisted alkaline calcium treatment process was optimized. The one-factor-at-a-time method was used to investigate the effects of Ca2+ concentration, vacuum degree and pre-pumping pH on the contents of different calcium forms (water-soluble Ca, sodium chloride-soluble Ca, hydrochloric acid-soluble Ca, and acetic acid-soluble Ca) and the contents of cell wall components (water-soluble pectin (WSP), chelator-soluble pectin (CSP), sodium carbonate-soluble pectin (NSP), and hemicellulose fraction (HF)) in Qinguan apples. Subsequently, the optimization with the contents of sodium chloride-soluble Ca and CSP as the response variables was carried out using a Box-Behnken design and Design-Expert 8.0 software. The results indicated that sodium chloride-soluble Ca and CSF were the most abundant of their respective kinds and were significantly affected by all the factors tested. Under optimized conditions as follows: Ca2+ concentration 2.0 g/L, vacuum degree 0.08 MPa and pre-pumping pH 2.8, the experimental contents of sodium chloride-soluble Ca and CSP were 55.26 and 17.45 mg/kg, respectively, in good agreement with the predicted values. This study can provide some theoretical information for regulating the softening of canned solid pack apples.

Key words: decompression pre-pumping, alkaline calcium, calcium forms, cell wall componets, canned solid pack apples