• แบ่งอุณหภูมิในการเก็บรักษาอาหารออกเป็นช่วงๆ ดังนี้ - ช่วง T 15-45 ˚C เป็น danger zone bact. เจริญอย่างรวดเร็ว ไม่ควรเก็บวัตถุดิบไว้ในช่วง T นี้ - ช่วง T 7-15 ˚C และช่วง T 45-63 ˚C bact. เจริญอย่างช้าๆ เก็บอาหารได้ไม่เกิน 2-4 ชั่วโมง - ช่วง T < 7 ˚C และ T > 63 ˚C แนะนำให้เก็บ รักษาอาหาร การใช้อุณหภูมิต่ำในการเก็บรักษาอาหาร• ป้องกัน หรือ ลดการเจริญของจุลินทรีย์ - ลดกิจกรรมของเอนไซม์ - ลดการงอกของสปอร์• ยืดอายุการเก็บรักษาวิธีการเก็บรักษาที่อุณหภูมิต่ำ• แช่น้ำแข็ง - อาหารทะเลสด เนื้อสัตว์ ผักผลไม้สดหั่น น้ำสลัด - อุณหภูมิผิวอาหาร 0-1 ˚C - ปัญหา : อุณหภูมิขึ้นๆ ลงๆ cross contamination • Refrigerator (Refrigeration) -Fresh food Processed foods ready to eat food. -4-5 ˚ C temperature. -Easy food spoilage (meat, fish) maintained that T < 4.4 ˚ C (~ 1 ˚ C). -Control of temperature, relative humidity between the food.• Frozen -Fresh fruit, vegetables, meat Fish, food processing -Use temperature: 10 ˚ C <- Home freezer -20 ˚C Dry ice-78 ˚ C Liquid nitrogen-196 ˚ C -Microbial growth that no-20 ˚ C, but may grow during defrost.The effect of low temperatures here microorganisms1. the function of the enzyme decreases, especially the heat-stable proteinase and lipase. -Enzyme were destroyed. -Proteins denature and coagulate Cell wall-elements of injury. -DNA. 2. the quantity of water applied microbial reduction -Aw of reduced food deficits may be dead M.O. -Ice crystals break cell. Cell wall tear Various substances flowing out of cells, cell death, M.O.• 0 to -1 ˚C -Exponential phase lag phase, Psychrophile:, germination time of spore. Mesophile Thermophile:-injuries and death, and• -2 ˚C -Free water in ice crystals occur curing foods. -T ice crystals aw The result of the frozen rate.• slow freezing -T < 5 ˚ C, 3 – 72 hours. -Crystal ice large -Solution effect occurs. -The water in the cells spread outside the cell lacks water. The intensity of the salon. Increased cell (aw) ion in the cell increases (pH) of the various structures in the cell waste products and does not retain the. -Cell injury.• quick freezing -T – 17.8-˚ C, 45.6 No more than 30 minutes. -Ice crystals small. -Effect does not occur, the cell solution. -Cell injury and death is less than.The result of the Freeze-Thaw• The Cell wall and cell membrane tear• DNA wire fracture• Ribosomal RNA damage conditions.• Some of the Enzyme was vetoed.• Sublethal (repairable) injury - Structural and functional injuries are reversible• Lethal injury - The damage are irreversible The use of high temperature (High Temperature).• Use heat or high temperatures to destroy the cell. Microbial • A break. - Pasteurization - SterilizationPasteurization• Thermal 100 ˚ C < T • Destroy the microorganisms that cause disease.• Reduce the number of microorganisms that cause food to spoil.• Temperature and duration. - 63 ˚C , 30 min (low temp, long time ; LTLT) - 72 ˚C, 15 sec (high temp, short time ; HTST) - 82.3 ˚C , 25 sec - 76.7-93.3 ˚C , 1-3 sec - 74 ˚C , 15 min• Heat sufficient to destroy. Mycobacterium tuberculosis and Coxiella burnetii- -Yeast, mold, and G + G-bact some varieties.Sterilization• Thermal 100 ˚ C T. • Destruction of all microorganisms, including sports• The quantity of heat that is used in this class are called commercial sterilization.• A food that has a commercial sterilized food. -Canned foods -UHT milk (135-150 ˚ C, 1-4 sec). Effect of microbial cell heat• Climate change-microbial cells with proteins (denature) or settling of a protein (coagulation) makes cells die.• Make the broken DNA.• Destruction of cytoplasm Factors that affect the thermal resistance of the microorganisms• The relationship between the temperature and the length of time to kill. Microbial • Default cell volume and spore• The composition of the food.• The type of microorganisms D-value• Minutes at level one, which destroys microorganisms, reduce down to 90% or one log cycle.Z-value• The temperature is changed because of changing D to 1 log cycle. F-value• Heat and the time required to destroy. Microorganisms in food products, access to the aseptic conditions commercial.
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