preservative

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preservative

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VAN LANG UNIVERSITY ENGLISH FOR BIOTECHNOLOGY Teacher: BA. Dương Thị Như Hiền Students: Trương Thị Thanh Diễm Lâm Thị Tú Mi Bùi Thị Hồng Phúc Hồ Thị Hương Thảo Nguyễn Thị Khánh Tuyên Lê Tấn Hưng FORMS OF VEGETABLE PRESERVATION 1)Freezing 2)Drying 3)Canning 4)Salt & sour vegetable 5)Other # • Discover food preservation techniques to store vegetables many months. Dry and store vegetables. Preserving garlic, onion, shallot, beans .How to for storing vegetables. • Food preservation and vegetable storage techniques including canning vegetables, freezing, pickling and drying or curing. • Storing vegetables properly can extend your food supply for many months. # # 1) Freezing & blanch # • Storage at low temperature slows many of the enzyme reactions involved in spoilage and reduces the growth rate of microorganisms (though it does not kill them). To minimize microbial growth, refrigerators should be kept at 0 0 C to 4 0 C and freezers at or below 0 0 C. Refrigeration is advantageous because it does not cause chemical or physical changes to food. # 0 0 C-4 0 C low temperature inhibits enzyme activity & microbial growth below 0 0 C Freezing it does not cause chemical or physical changes to food. the water in vegetables expands and forms ice crystals The structure of plant and animal cells are disrupted # The greatest disadvantage of freezing is that the water in food expands and forms ice crystals. The ice crystals formation disrupts the structure of plant and animal cells, giving frozen food a softer texture after thawing. Newer technologies in which freezing occurs more rapidly help minimize this problem: faster freezing means that smaller ice crystal form, resulting in less damage to cells. # • Preserving vegetables by freezing retains more of the vegetable's nutrient value than canning. While canning may be more economical, freezing preserves more of the vegetable’s nutrient value. • Tips for Vegetable Freezing Success:  Use young, tender vegetables at their peak.  Freeze as soon after harvesting as possible.  Use the best quality freezer bags or containers to prevent freezer burn

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