Food Preservation Techniques and Principles

Food preservation aims to extend shelf life, ensure food safety, and maintain nutritional quality.

Food preservation methods can be broadly categorized as inactivation of microorganisms and enzymes, inhibition of microbial growth, and avoidance of recontamination.

Thermal processing involves applying heat at specific temperatures and durations to eliminate microorganisms and enzymes in food. These temperature and time combinations are crucial for effective preservation.

<p>Simply damaging microorganisms may not be sufficient as they can potentially resuscitate and continue to spoil the food. Complete destruction of the microorganisms is essential for long-term preservation.</p> Signup and view all the answers

<p>Polyphenol oxidase leads to oxidative browning, Lipoxygenase causes oxidation of unsaturated fatty acids, and Proteases degrade proteins, weakening the gel structure of the food.</p> Signup and view all the answers

<p>Blanching is a heat treatment applied to fruits and vegetables, typically by exposing them to hot water or steam for a set period. It deactivates enzymes, reduces harmful microorganisms, and softens the tissue for further processing.</p> Signup and view all the answers

<p>Blanching deactivates enzymes like polyphenoloxidase and lipoxygenase, preventing browning and detrimental oxidation. It also reduces microbial contamination, maximizing the shelf life of the treated produce.</p> Signup and view all the answers

<p>Blanching deactivates enzymes, reduces microbial contamination, and softens the tissue for easier further processing and improves the overall effectiveness of the preservation process.</p> Signup and view all the answers

<p>Pasteurization aims to destroy pathogenic microorganisms and reduce spoilage microbes to extend shelf life while preserving quality. Sterilization aims to completely destroy all microorganisms, including spores, to achieve commercial sterility for a long-term, shelf-stable product.</p> Signup and view all the answers

<p>Commercial sterility means the food is free from harmful microorganisms that can cause illness or spoilage. While some heat-resistant spores may remain, they won't multiply under typical storage conditions.</p> Signup and view all the answers

<p>UHT treatment involves heating milk to 138°C for 2 seconds, followed by rapid cooling to 10°C. This high temperature ensures the destruction of microorganisms, achieving commercial sterility.</p> Signup and view all the answers

<p>TDT refers to the specific combination of time and temperature needed to destroy the spores of Clostridium botulinum, a potentially deadly pathogen, at the coldest point of a food product.</p> Signup and view all the answers

<p>TDT ensures that the processing conditions eliminate the spores of Clostridium botulinum, which can produce a deadly toxin in canned food. This reduces the risk of botulism poisoning.</p> Signup and view all the answers

<p>Factors such as the pH of the food, its thickness or viscosity, the size of food particles, the container's dimensions, and the temperature of the cooking medium can all affect how heat transfers through the can.</p> Signup and view all the answers

<p>Pasteurization typically employs lower temperatures, ranging from 60 to 85°C, while sterilization requires higher temperatures, often exceeding 100°C, reaching 121°C for canned foods under pressure.</p> Signup and view all the answers

<p>Retort sterilization is frequently used for processing canned foods like fruits, vegetables, and meats. It involves heating the sealed cans in a retort, a pressure vessel, at temperatures above 100°C to achieve commercial sterility.</p> Signup and view all the answers

<p>Blanching is a heat treatment used to inactivate enzymes that could cause undesired changes in the food product during processing or storage. One example is blanching vegetables before freezing to stop enzymatic browning and maintain color and texture.</p> Signup and view all the answers

<p>Pasteurization aims to destroy harmful microorganisms while preserving the product's quality, extending its shelf life, and requiring refrigeration. It's common for milk and fruit juices. Sterilization, on the other hand, aims to eliminate all microorganisms, resulting in a longer shelf life without refrigeration. It's used for canned goods and UHT milk.</p> Signup and view all the answers

<p>The effectiveness of pasteurization relies on the principle that heat kills microorganisms. The different pasteurization methods, like holding and HTST, vary in the temperature and time required to achieve the desired level of microbial inactivation. Higher temperatures require shorter treatment times.</p> Signup and view all the answers

<p>Pasteurization primarily destroys vegetative pathogens and reduces spoilage organisms, while sterilization kills all microorganisms, including heat-resistant spores.</p> Signup and view all the answers

<p>The two main methods are chilling and freezing. Chilling slows down microbial growth, enzymatic activity, and chemical reactions by reducing temperatures to between 8 – 0 oC. Freezing further reduces these processes by lowering temperatures to -18 or -25 oC.</p> Signup and view all the answers

<p>Commercial sterility refers to a level of microbial reduction that ensures the food product is safe for consumption and has a reasonable shelf life, even though it may contain a few surviving microorganisms. This is often preferred to complete sterilization because it can minimize the negative effects of high heat on the food's quality.</p> Signup and view all the answers

<p>Chilling typically occurs between 8 – 0 oC. This temperature range helps to slow down the rate of biochemical and microbiological changes in food, extending its shelf life.</p> Signup and view all the answers

<p>The holding method pasteurizes milk by heating it to 63°C for 30 minutes, while the HTST (high-temperature short-time) method heats it to 72°C for 15 seconds. Both methods effectively kill harmful microorganisms.</p> Signup and view all the answers

<p>Pasteurization results in a moderately extended shelf life, typically requiring refrigeration, while sterilization allows for long shelf life without refrigeration.</p> Signup and view all the answers

<p>Industrial steam provides efficient and consistent heat transfer, allowing for rapid blanching of large batches of food. It also helps to reduce the risk of contamination and ensures uniform heat distribution.</p> Signup and view all the answers

<p>Pasteurized products include milk and fruit juices. Sterilized products include canned foods and UHT milk.</p> Signup and view all the answers

<p>The steam temperature and the duration of exposure to steam are crucial factors. Higher temperatures and longer exposure times generally lead to more effective blanching.</p> Signup and view all the answers

<p>Pasteurization results in minimal nutrient loss, retaining most vitamins and flavor due to mild heat. Sterilization, on the other hand, leads to greater nutrient loss and sensory changes due to high temperatures.</p> Signup and view all the answers

<p>The key considerations are the desired shelf life, susceptibility of the food to heat damage, and storage conditions. Sterilization provides longer shelf life but can potentially affect food quality. Pasteurization is suitable for products requiring shorter shelf life and refrigeration storage.</p> Signup and view all the answers

<p>Pasteurized foods typically require refrigerated storage after processing. Sterilized foods, being commercially sterile, allow for room temperature storage.</p> Signup and view all the answers

<p>Thermophilic microorganisms, with an optimal temperature range of 55 – 65 oC, thrive in high temperatures. Psychrotrophic microorganisms, on the other hand, can grow at low temperatures, with a minimum growth temperature below 0 oC.</p> Signup and view all the answers