摘要
In this study, a processing technology to preserve green color and firmness was developed to solve the quality problem of blanched green leafy vegetables during thermal storing (≥60℃. Firstly, the effects of sodium bicarbonate concentration, calcium ascorbate concentration, blanching time, calcium chloride concentration and immersing time on color and hardness of blanched green leafy vegetables were studied by single factor experiment. Secondly, factorial design was applied to select significant factors, including sodium bicarbonate concentration, blanching time and calcium chloride concentration. Finally, the processing conditions were optimized by response surface based on central composite design. The results showed that the optimal processing conditions were as follows: sodium bicarbonate concentration of 0.4% (m/m), calcium ascorbate concentration of 0.01% (m/m), blanching time of 50 s, calcium chloride concentration of 0.1% (m/m) and immersing time of 35 min. The optimal conditions were validated by four kinds of common green leafy vegetables. After thermal storage for 4 h, all color difference Δa* decreased and the lowest one was -5.59±0.33, the highest retention rate of chlorophyll was 170%, this effect was most significant 2 hours before preservation. The firmness increased in two kinds of common green leafy vegetables, the highest firmness reached 47.49±1.67 N. All green leafy vegetables showed good sensory quality under the optimal conditions. This processing technology can preserve the color and firmness of blanched green leafy vegetables effectively. The optimal processing conditions can provide important technical support for the processing of green leafy vegetables in bento.
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