A Comparative Study of Three Types of Vegetables During the Vacuum Precooling Process
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Abstract:
Cabbage (Brassica oleracea L. var. capitata L), Chinese cabbage (B. rapa pekinensis), and flowering cabbage (B. campestris L. ssp.chinensis var.utilis Tsen et Lee) were treated with vacuum precooling under different precooling final pressures and processing loads. The effects of leaf wrapping shape, compactness, non-vein leaf ratio, and leaf thickness on the precooling time, weight loss rate, and temperature difference were investigated. The results showed that three types of leafy vegetables (2400 g) were quickly cooled by vacuum precooling to 4℃ in less than 25 min with a precooling final pressure of 500 Pa. Significant differences (p < 0.05) in cooling time, weight loss, and temperature differences among cabbage, Chinese cabbage, and flowering cabbage were observed during the vacuum cooling process at various pressures and processing loads. The wrapping shape and compactness of cabbages affected the precooling time and temperature, and the other tissue characteristics of leaves, including the non-vein ratio and thickness, had major effects on weight loss during vacuum precooling. The morphological structure of the leaf was an important factor affecting the vacuum precooling process, and the final pressure and processing load during vacuum cooling could be determined based on the morphological characteristics of the specific vegetable.
