Food Processing Chap.4

Processed Foods Chapter 4 Overview Scenarios Benefits of processing Types of processing Consequences of processing Scenarios Martin and Laura Interviews of ?older? person Recollections of parent and grandparent Features the 60?s and 70?s What are Processed Foods? Processed foods are products that have been preserved so they will not spoil as quickly as fresh, whole foods Most raw materials are perishable and require processing to prevent loss shelf stable products are foods that may be kept at room temperature Why are Foods Processed? The primary reason is to reduce or eliminate harmful microbes Another reason is to stop the loss of nutrients due to enzyme action Common methods Sterilizing Pasteurizing Fermenting Blanching Benefits of Processing Processed food is more likely to be eaten Shelf stable foods are ready when we are Loss of nutrients and quality is slower Processed foods have less waste Processed foods take more energy to produce, but use less energy to store Processing Steps Unit operations are distinct steps for converting raw materials into processed foods Examples of unit operations Material handling Cleaning Pumping Mixing Heat exchanging Packaging Types of Processed Foods Processed whole foods Canned peas, corn oil, orange juice Formulated foods Bread, jam, chocolates, Chilled foods Ice cream, deli meats, margarine Prepared foods Pizza, potato salad, food service Major Types of Processes Heating Freezing Drying Concentrating Curing Milling Extracting Fermenting Irradiating (it wont keep microbes away pemently). Heating Cooking kills spoilage and pathogenic microbes but does not sterilize food Blanching is a unit operation to inactivate enzymes Pasteurization kills pathogens but not all spoilage microbes Canning sterilizes product in a container Aseptic processing sterilizes product prior to packaging Canning Considerations Types of microbes Clostridium botulinum, Bacillus stearothermophilus Headspace vacuum Heat treatment Cold point Acidity of product (USDA says a 4.6 pH level is the magic number when it comes to the acidity of the product.) Heat Treatment Conduction (spam) involves heat transfer through a material due to molecular movement Convections (can peas)(foods in fluid)i.e. cooking macoroni involves heat transfer through movement of heated fluid from hot regions to cold Conducted in a retort or pressure cooker Acidity Factors The acidity or pH of a product affects the amount of heat treatment needed Low acid foods are those with a pH greater than 4.6 and aw of 0.85 or more Acid foods are those that have a natural pH of 4.6 or less Acidified foods low acid foods to which acids are added so the pH is 4.6 or less and aw of 0.85 or more Freezing Freezing is a mild treatment that results in less loss of nutrients and quality than heat treatment Freezing slows the growth of microbes but does not kill them so there may be safety and spoilage problems when thawed Freezing Methods Still air Forced (blast) air Indirect contact Scraped surface Individual Quick Freeze (IQF) Cryogenic Drying Removing moisture reduces the ability for microbes to grow Even dry foods (flour) contain moisture (10-15%) Water activity (Aw) refers to water that is available for microbial growth Moisture content is not the same as water activity! Drying Methods Sun or air Oven Vacuum Spray Freeze Drum Concentrating Removal of water from a liquid food without changing it into a solid is concentration Common examples are juice concentrates and syrups Curing Curing is another way to decrease availability of water by adding preservatives Salt and sugar are the most common choices Sodium nitrite and sodium nitrate are additional curing agents applied to cured meat products Milling Cereal grains are milled into flour to improve digestibility Dry milling separates the seed into fractions based on anatomical structure (bran, germ, endosperm) Wet milling separates components on anatomical and solubility differences (protein, oil and starch) Dry milling Choice of method depends on desired product Abrasive mill Hammer mill Wheat Rice Polished Rice Corn Flaking Grits Brewers Grits Flour Roller mill Corn grain Steeping 30-50 hr, 50 C Coarse grinding Separator Sieving Centrifugal separator Drying Germ Bran Corn oil Gluten Starch Wet Milling Extracting Extracting involves the removal of a portion from the raw material Coffee and tea are common examples Other examples include juices, oils and flavors Oil Extraction and Processing Steps Pressing Refining Degumming Bleaching Deodorization Hydrogenation, Interesterification Terms Pressing is the mechanical squeezing of oil from oilseeds Deodorization is the application of steam in a vacuum to strip odor-causing low molecular weight compounds from oils Bleaching is the removal of colored substances from the oil using diatomaceous earth clays at 194°F Degumming is the removal of phospholipids by water at 122-140°F More Terms Hydrogenation is the process of saturating double bonds to increase the melting temperature of the oil Interesterification is the rearrangement of fatty acids on the oil to affect its melting temperature Oils and Fats Fats are usually solid at room temperature Oils are usually liquid at room temperature All food lipids are mixtures of triglycerides Mixtures result in melting temperatures that are a range (120-130° F) rather than specific (128° F) Fermenting This is one process that depends on the growth of microorganisms A starter culture is added to a perishable raw material to change it into a more stable food product Lactic acid and ethanol are the main preservatives Fermented Products Yogurt Bread Olives Pickles Salami Sauerkraut Beer and wine Irradiating Irradiation is a potent killer of microbes and can be used for foods as it induces little or no heat Radiation can be applied at high doses to sterilize a product or may be used at low doses (radurization) to be the equivalent of pasteurization Irradiating Sources Gamma radiation from cobalt has great penetration capability but requires elaborate safety measures Electron-beam radiation has less penetration capability but fewer health risks Other Processes High-pressure treatment Extrusion Roasting Microwave heating Ohmic heating Extrusion A forming technique whereby a material is forced, by compression, through a shaped opening in a die to produce a continuous profile A versatile, energy efficient and economical means to produce a wide variety of products Cereals are mostly extruded to produce snacks, or pellets for feed Raw material Product Some extruded products Soy ?meat? ?Cheerios? Potato chips ?Cheetos? Pasta Spaghetti Consequences of Processing Shelf life Nutrition Quality Safety Packaging Shelf Life Shelf life is the length of time that a product may be kept before it should be discarded It is related to safety but it is most closely related to spoilage Many processes are intended to increase shelf life by reducing or eliminating microbes Nutrition Extension of shelf life may accompany a decrease in nutritional value of foods Washing, drying, heating, exposure to light or oxygen are contributors to the loss of vitamins and minerals in foods Processed foods do provide nutritional value Quality Color, flavor and texture of processed foods are not the same as for fresh whole foods Compared to the prospect of spoiled food, the quality of processed food is quite good Safety Safety is the most important consideration in the design of a food process Processing is not a substitute for poor sanitary practices Sterilized foods (canned, irradiated) may be the safest but are a poor substitute for enjoying a variety of foods (with inherent risk) Packaging Preservation techniques may slow or stop spoilage, but packaging prevents recontamination by microbes or chemicals Packaging a0k-llso functions to keep water, odors and gases in the product while excluding water, oxygen, odors and light Remember This! The main function of a package is to prevent microbial of chemical contamination of a processed food Food is preserved to make it safer by eliminating harmful microbes The greater the destruction of microbes, the greater the shelf life Unit operations are distinct steps