Microbiology - Food Microbiology - Quick Guides | Microbiology

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Study GuideMicrobiology–Food Microbiology1.Food PreservationFood preservation includes methods used toprevent food spoilageandprotect food from harmfulmicroorganisms. These methods work in three main ways:1.Keeping microorganismsout of food2.Removingmicroorganisms already present3.Slowing or stoppingthe growth of microorganisms in foodUsing the right preservation method helps food stay safe, fresh, and nutritious for longer periods.1.1Preventing ContaminationThe first step in food preservation is preventing microorganisms from entering food in the first place.This is done by:•Sterilizing and sanitizingequipment•Maintaining cleanliness during food preparation•Sealing foodsin protective packagingMicroorganisms can also be removed by:•Filtering or sedimentingliquid foods•Washingfruits and vegetables•Trimmingcontaminated parts from meat and poultry1.2Heat PreservationHeat is one of the most effective ways to preserve food because itkills microorganisms.

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Study GuideKey Factors in Heat Treatment•Thenumber of microorganismspresent (microbial load)•Thetype of microorganismoBacterial spores are much more resistant than active (vegetative) cells•Acidityof the food (higher acidity increases effectiveness)Types of Heat TreatmentsThere are three main heat-based preservation methods:1.Pasteurizationo62°C for 30 minutesoro72°C for 15–17 secondsThis reduces harmful microbes without seriously affecting food quality.2.Hot FillingoLiquids and juices are boiledoThen poured into containers while hot3.Canning (Steam Under Pressure)oUses high heat and pressure to kill even resistant microorganismsThe effectiveness of heat is measured usingthermal death time, which is the time needed at aspecific temperature to kill a certain number of microorganisms.Steps in the Canning Process•Food is washed to remove dirt•Blanchingbriefly heats food to stop enzyme activity•Damaged sections are removed•Food is sealed in cans•Cans are heated in aretortat controlled temperature and time

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Study Guide1.3Low-Temperature PreservationCold temperatures slow microbial growth by reducingenzyme activity, but they do not kill allmicroorganisms.RefrigerationSome bacteria, calledpsychrophiles, can still grow in the cold. Common examples belong to:•Pseudomonas•Alcaligenes•Micrococcus•FlavobacteriumFungi can also grow at refrigerator temperatures.Freezing•Slow freezingandquick freezingare used for long-term storage•Freezing reduces microbial numbers but does not eliminate them•Ice crystals damage microbial cells•Increased solute concentration in unfrozen water causes protein damage1.4Chemical PreservationCertain chemicals slow or stop microbial growth and are safe for human consumption.Common preservatives include:•Propionic acid•Sorbic acid•Benzoic acid•Sulfur dioxideSomeantibiotics, such as tetracycline, are used to preserve meats where regulations allow. Theseresidues usually disappear during storage and cooking.

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Study GuideNatural PreservativesMany foods naturally preserve themselves:•Sauerkrautuses lactic and acetic acids•Fermented milk products(yogurt, sour cream) rely on acids produced by bacteriaThese traditional methods have been used for centuries.1.5DryingDrying preserves food byremoving water, which microorganisms need to survive.Methods include:•Sun drying•Belt, tunnel, and cabinet dryers (used in industry)•Freeze-drying (lyophilization), which removes moisture while keeping food lightweight andstable1.6Radiation PreservationRadiation can reduce microbial contamination without heating food.•Ultraviolet (UV) radiationis used to disinfect food surfaces•Ionizing radiation(such as gamma rays) is used for certain fruits, vegetables, and spices,following safety regulationsKey TakeawayFood preservation works by controlling microorganisms through heat, cold, chemicals, drying, andradiation. Understanding how these methods function helps ensure food safety, reduce waste, andprotect public health.

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