Food Processing & Preservation Exam PDF

Food Preservation Extending shelf life, ensuring food safety, maintaining nutritional quality.  Food processing makes low- quality foods better Food processing helps to preserve foods quality Methods of preservation Inactivation of microorganisms and/or enzymes Inhibition of...

Food Preservation Extending shelf life, ensuring food safety, maintaining nutritional quality.  Food processing makes low- quality foods better Food processing helps to preserve foods quality Methods of preservation Inactivation of microorganisms and/or enzymes Inhibition of microbial growth or deterioration of quality Avoidance of recontamination of foods at all steps  Thermal processing Thermal processing is defined as the combination of temperature and time (critical parameters) required to eliminate a desired number of microorganisms and enzymes from a food product. to modify texture and flavour of a food product. to extend shelf life of a food product  To target both spoilage and pathogenic organisms and seeks to destroy their spores. Damage the cells is insufficient, the cells must be killed! Damaged cells may resuscitate!! Examples: Clostridium botulinum, E.coli, Listeria monocytogenes….. List of harmful enzymes in food: 1. Polyphenol oxidase 5. Peroxidase - oxidize phenolic compounds - oxidize pigments, flavours, 2. Lipoxygenase vitamins - oxidize unsaturated 6. Proteases fatty acids - degrade proteins, weaken gel 3. Pectin Methylesterase 7. Lipase - de-esterifies pectin - breakdown fats into free fatty 4. Amylase acids - degrade starch molecules 8. Cellulase - degrade cellulose leading to softening. Blanching (a simple thermal processing) – as a pre-treatment A type of heat treatment applied to fruits and vegetables. Commonly carried out by exposing the commodity at a pre-set temperature (85-95oC), and holding it for a pre-set time (2-10 min), before cooling it rapidly. The heating medium can be steam or hot-water. Serves various function: a. To deactivate enzymes (eg. Lipoxygenase, polyphenoloxidase, polygalacturonase, etc.) b. To reduce number of contaminants microorganisms. c. To soften tissue to facilitate subsequent processing.  Home blanching  Industrial steam blanching https://www.youtube.com/watch?v=2sb5OxfYyaI Where hot steam will be flushed down onto the commodity, and the speed of travelling through the tunnel will determine the adequacy of the blanching treatment. http://foodtechinfo.com/foodpro/index_gas_technologies/blancher_-_tubular/ https://drivemehungry.com/chinese-style- dry-fried-garlic-green-beans/  Pasteurization vs sterilization Pasteurization:Low-temperature short-time (LTLT) and high-temperature short-time (HTST). - Applications: Milk, fruit juices. SterilizationComplete destruction of all microorganisms. -Examples: Canned foods, UHT milk. 3 months self life under chilling storage Sterilized products 2 years self life under ambient temperature Pasteurization A heat treatment (80-90 oC) meant to kill potential harmful microorganisms, without seriously reducing the quality of the product. Still contain many living organisms. Must be stored under refrigeration to inhibit growth of surviving organisms. Two objectives: (a) For milk and liquid eggs: to specifically destroy organisms known to occur in these foods that could affect public health. (b) To extend shelf life from a microbial and enzymatic point of view The higher the temperature, the shorter the time required to kill the microorganisms. Methods for pasteurized MILK: (a) Holding method – heat to 63 oC, hold for 30 min, quick cooling to 7 oC. (b) HTST method (high-temperature short time, known as flash pasteurization) - heat to 72 oC, hold for 15 seconds, quick cooling to 10 oC. Pasteurized milk processing line http://www.drinkproductionline.com/sale-10365888-automatic-pasteurized-milk-processing-line- yogurt-production-line-equipment-6000-10000lph.html Sterilization Refers to complete destruction of microorganisms. # The time to achieve true sterility could be several hours. However, this length of exposure to high heat would cause undesirable quality changes in the food components. # So, many foods need not be completely sterile to be safe and have a reasonable shelf life. These foods are treated to achieve commercial sterility rather than to achieve total sterility. Normally requires 121 oC (250 oF) of wet heat for 15 minutes or its equivalent. For milk product UHT method (Ultrahigh-temperature) - heat to 138 oC, hold for 2 seconds, quick cooling to 10 oC. Canning to achieve commercial sterility a. Commercial sterile means the degree of sterilization at which all pathogenic or toxin-producing organisms are destroyed, as well as any spoilage organisms. b. It may contain small number of heat-resistant bacterial spores, but these will not multiply under usual conditions within the food. c. Canned food have a shelf life of 2 years or more. d. To achieve commercial sterility, specific heating time and temperature, known as thermal death time (TDT) during a canning process is essential for a specific product. Note: Spores refers to an inactive, dormant, or seed-like “resting”phase.  What is TDT ? The identified processing time and temperature required to destroy the spores of Clostridium botulinum at the cold point of a product. Pathogenic, releasing a deadly toxin into canned food. Why is TDT important? Why is TDT important? # This is because in a can, there may be a relatively slow transfer of heat depending on several factors The pH of the food The thickness or viscosity of the product The size of the food particles The dimension of the container The temperature of the cooking medium Retort sterilization https://datatrace.mesalabs.com/2014/09/22/retort-sterilization-in-food-processing/ Aspect Pasteurization Sterilization A heat treatment process designed to destroy pathogenic microorganisms and reduce A process that completely destroys all microorganisms (pathogens, spoilage Definition spoilage microbes to extend shelf life while preserving quality. microbes, and spores) to achieve commercial sterility of food. To make food safe for consumption and extend shelf life without significantly affecting To ensure food safety by eliminating all microbial activity, including spores, for a Objective its sensory and nutritional properties. long-term, shelf-stable product. High temperatures, typically above 100°C (e.g., 121°C for canned foods under Temperature Range Lower temperatures, usually between 60–85°C for liquids like milk and juices. pressure). Shorter time, typically a few seconds to minutes (e.g., 15 seconds for high-temperature Longer time, depending on the food product (e.g., 15–20 minutes at 121°C for Processing Time short-time pasteurization (HTST)). sterilization in pressure canning). Destroys only vegetative pathogens and reduces spoilage organisms. Does not eliminate Kills all microorganisms, including spores of heat-resistant bacteria (e.g., Clostridium Microbial Target heat-resistant spores. botulinum). Shelf Life Moderately extended shelf life (e.g., milk: 7–20 days under refrigeration). Long shelf life without refrigeration (e.g., canned food: months to years). Used for canned foods, UHT (Ultra High Temperature) milk, and medical products Applications Commonly used for milk, fruit juices, beer, and liquid eggs. like surgical instruments. Effect on Nutrients Minimal nutrient loss, retains most vitamins and flavor due to mild heat. Greater nutrient loss and sensory changes due to high temperatures. Packaging Typically requires refrigerated storage after pasteurization. Allows room temperature storage as the product is commercially sterile.  Low-temperature processing Low-temperature processing involves storing or treating food at temperatures below ambient to slow down microbial growth, enzymatic activity, and chemical reactions. The two main methods are chilling and freezing. Commercial refrigerator temperature = < 10 oC Commercial freezer temperature = -18 or -25 oC Slowing down reaction by chilling Slowing reaction by chilling Temperatures typically between 8 – 0 oC. It is used to reduce the rate of biochemical and microbiological changes, and thus help to extend the shelf life of fresh and processed foods. There are four broad categories of microorganisms based on the temperature range for growth: Chilling (a) thermophilic (minimum 30-40 oC, optimum 55 – 65 oC) Freezing (b) mesophilic ( minimum 5-10 oC, optimum 30-40 oC) (c) psychrotrophic (minimum