Chapter 4: Processed Foods Flashcards
Processed Foods
Products that have been preserved so they will not spoil as quickly as fresh, whole foods
Perishable
Most raw materials are this and require processing to prevent loss
Shelf Stable Products
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
Methods of Processing Foods
o Sterilizing
o Pasteurizing
o Fermenting
o 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
Unit Operations
Distinct steps for converting raw materials into processed foods
Examples of Unit Operations
o Material handling o Cleaning o Pumping o Mixing o Heat exchanging o Packaging
Processed Whole Foods
oCanned peas, corn oil, orange juice
Formulated Foods
o Bread, jam, chocolates
Chilled Foods
Bread, jam, chocolates
Prepared Foods
o Pizza, potato salad, food service
Types of Processing
- Heating
- Freezing
- Drying
- Concentrating
- Curing
- Milling
- Extracting
- Fermenting
- Irradiating
Cooking
Kills spoilage and pathogenic microbes but does not sterilize food
Blanching
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
o Clostridium botulinum, Bacillus stearothermophilus
• Headspace vacuum
• Heat treatment
o Cold point
• Acidity of productConduction
Involves heat transfer through a material due to molecular movement
Convection
Involves heat transfer through movement of heated fluid from hot regions to cold
Acidity Factors
The acidity or pH of a product affects the amount of heat treatment needed
Low Acid Foods
Those with a pH greater than 4.6 and aw of 0.85 or more
Acid Food
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
Drying Methods
- Sun or air
- Oven
- Vacuum
- Spray
- Freeze
- Drum
Concentrating
- Removal of water from a liquid food without changing it into a solid
- Common examples are juice concentrates and syrups
Curing
Another way to decrease availability of water by adding preservatives
• Salt and sugar are the most common choices
Sodium Nitrite and Nitrate
Additional curing agents applied to cured meat products
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)
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
Pressing
The mechanical squeezing of oil from oil seeds
Deodorization
The application of steam in a vacuum to strip odor-causing low molecular weight compounds from oils
Bleaching
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
Hydrogenation
The process of saturating double bonds to increase the melting temperature of the oil
Fats
Usually solid at room temperature
Oils
usually liquid at room temperature
Triglycerides
Food lipids are mixtures of this. 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
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
Cobalt has great penetration capability but requires elaborate safety measures
Irradiating Sources: Electron-beam radiation
Less penetration capability but fewer health risks
Irradiating Sources
- 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
Consequences of Processing
- Shelf life
- Nutrition
- Quality
- Safety
- Packaging
Shelf Life
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
Safety
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 also functions to keep water, odors and gases in the product while excluding water, oxygen, odors and light
Interesterification
is the rearrangement of fatty acids on the oil to affect its melting temperature
