2009 Low Temp Preservation of Foods

2009 Low Temp Preservation of Foods - The origin of...

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The origin of refrigeration? (and who said research was easy !?)
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Low Temperature Preservation of Foods Refrigeration Freezing Objectives of refrigeration / freezing: 1. Slow microbial growth     Microorganisms can cause:    Flavor, odor changes Appearance changes (secrete pigments or enzymes which degrade color) Texture changes (secretion of enzymes which break down proteins, fibers) Pathogenic conditions   2. Slow or stop enzymatic / chemical reactions
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Refrigeration Preservation of Foods A. Refrigeration of Meats, Poultry, Fish Optimum temp = -1 to + 2° C (just above freezing pt) Major objective: prevention of microbial growth     B. Refrigeration of Plant Foods More problematic than meats Challenge : Plant foods are alive (unlike meats) Quality depends on management of certain biochemical processes of living tissues
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After harvest, many physiological processes continue : 1. Respiration O 2 organic molecules energy (ATP) + CO 2 + heat (starch) 2. Synthesis of hormones, pigments, enzymes 3. Changes in cell wall structure Enzymatic degradation of pectins, cellulose may lead to softening
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  Important quality attributes:   Crispness                  Succulence                Crunchiness  Texture of fresh plant foods due to two factors : 1. Structure and condition of cell walls Thickness and strength Adhesion to adjacent cells 2. Cell "turgor pressure" Water pressure inside cell >> outside Because solute conc. inside > outside, water moves from outside to inside ( osmotic pressure ) Maintenance of turgor pressure requires: * intact cell membranes, cell walls * energy (ATP)
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* Slow rate of respiration, other biochemical processes, prolong shelf life , yet * Allow sufficient energy production to maintain essential cellular processes Decr. temp. Decr. respiration rate Increase storage life
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This note was uploaded on 02/16/2010 for the course NS 3450 at Cornell University (Engineering School).

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2009 Low Temp Preservation of Foods - The origin of...

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