9 Questions
What is the main purpose of blanching fruits and vegetables?
To extend shelf life
Which factor does NOT influence blanching time?
Temperature of the surrounding environment
What is an advantage of using steam blanchers over hot-water blanchers?
Energy Efficiency
Which is a disadvantage of hot-water blanchers compared to steam blanchers?
Slower Heating
What effect does blanching have on the texture of fruits and vegetables?
It leads to longer texture due to longer exposure to heat
Which statement best describes the impact of blanching on color and flavor of foods?
It reduces color vibrancy and flavor intensity
Which factor is NOT a reason for using steam blanchers over hot-water blanchers?
Uniform Heating
How does the blanching process affect the enzymic activity in vegetables?
It decreases enzymic activity
What is a potential issue related to texture that can arise from using hot-water blanchers?
Prolonged Texture Loss
Study Notes
Pasteurization
- Used to extend the shelf life of acidic foods (pH < 4.5) by destruction of spoilage micro-organisms and enzyme inactivation
- Sensible heat required to raise the temperature of a liquid during pasteurization is calculated using Q= mc (θA-θB)
- Equipment used for pasteurization of packaged foods includes glass containers, metal and plastic containers, and steam-air mixtures or hot water
Pasteurization of Unpackaged Foods
- Swept Surface Heat Exchangers or Open Boiling Pans are used for small-scale batch pasteurization of liquid foods
- Plate Heat Exchangers are used for large-scale pasteurization of low viscosity liquids
- Concentric Tube Heat Exchangers are suitable for more viscous foods
Effect on Foods
- Minor changes to nutritional and sensory characteristics of most foods
- Shelf life of pasteurized foods is usually extended by a few days or weeks
- Heat treatment is less severe and changes in food quality are less
- Ensures adequate enzyme inactivation and prevents excessive softening and loss of flavor in food
Blanching
- Briefly immersing food products in boiling water or steam, followed by rapid cooling
- Improves quality and shelf life of fruits, vegetables, and other food items
- Destroys enzymic activity in vegetables and some fruits prior to further processing
- Not intended as a sole method of preservation but as a pre-treatment
Factors Affecting Blanching
- Type of fruit or vegetable
- Size of the pieces of food
- Blanching temperature
- Method of heating
Equipment Used in Blanching
- Steam Blanchers: provide precise temperature control, heat the product more quickly, and are more energy-efficient
- Hot-water Blanchers: use hot water to heat the product, temperature control can be slightly more challenging, and may take longer to heat the product
Effects of Blanching on Food
- Causes some changes to sensory and nutritional qualities
- Minerals, water-soluble vitamins, and other soluble components are lost during blanching
- Factors that influence vitamin loss include maturity of food, method of preparation, surface area-volume ratio, and method of blanching
- Blanching can brighten the color of some foods by removing air and dust on the surface
- Texture of vegetables is softened by blanching to facilitate filling into containers prior to canning
Test your knowledge on the process of pasteurization of packaged foods, focusing on the specific heat transfer and temperature changes involved. Explore how this process helps extend the shelf life of acidic foods by destroying microorganisms and enzymes.
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