Ice-crystal formation in gelatin gel during pressure shift versus conventional freezing
Ice-crystal formation in gelatin gel during pressure shift versus conventional freezing
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DOI：
10.1016/j.jfoodeng.2004.02.035
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发表时间：
2005-01-01
影响因子：
5.5
通讯作者：
Le Bail, A
中科院分区：
文献类型：
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作者：
Zhu, SM;Ramaswamy, HS;Le Bail, A
采用100 MPa（-8.4℃）、150 MPa（-14℃）和200 MPa（-20℃）压力变换冷冻（PSF）以及常规空气冷冻（CAF）和-20℃液体浸泡冷冻（LIF）对明胶凝胶（2%明胶，w/w）圆柱形样品（7.8 mm直径，35 mm长）进行冷冻。收集凝胶样品在冷冻过程中的压力和温度曲线。对冷冻明胶冷冻干燥后的卵形冰晶的面积、等效直径、圆度和伸长率进行了评价。在100、150和200 MPa的CAF、LIF和PSF作用下，样品的冰晶等效直径（平均+/- s.d）分别为145 +/- 66、84 +/- 26、91 +/- 30、73 +/- 29和44 +/- 16 μ m。圆度和伸长率有一定的变化，在不同的冷冻技术下没有明显的变化趋势。用模型食品（明胶凝胶）进行的研究结果证实，PSF过程促进了冷冻样品中大量小冰晶的产生，有助于保持产品更好的质地。(C) 2004 Elsevier Ltd.版权所有。
Cylindrical specimens (7.8 mm diameter, 35 mm length) of gelatin gel (2% gelatin, w/w) were frozen by pressure shift freezing (PSF) at 100 MPa (-8.4 degreesC), 150 MPa (-14 degreesC) and 200 MPa (-20 degreesC) as well as conventional air freezing (CAF) and liquid immersion freezing (LIF) at -20 degreesC. Pressure and temperature profiles of gel samples were gathered during the freezing process. The ovoid microstructure of ice crystals in frozen gelatin gels after freeze-drying was evaluated for area, equivalent diameter, roundness and elongation. Equivalent diameter (mean +/- s.d.) of the ice crystals was 145 +/- 66, 84 +/- 26, 91 +/- 30, 73 +/- 29, and 44 +/- 16 mum for test samples subjected to CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. Roundness and elongation were somewhat variable and did not show a clear trend with the different freezing techniques. Results from this study with a model food (gelatin gel) confirm that the PSF process promotes the production of larger number of smaller ice crystal in the frozen sample that help to retain a better texture in the product. (C) 2004 Elsevier Ltd. All rights reserved.