L5 Processing of Fruits & Vegetables
Recommended freezing temperature for perishable goods
-30-0
Why are fruit juices harder to dry than proteins or starch based foods?
-At low moisture levels, very hygroscopic, picks up moisture easily. Needs to rapidly packed into hermetically sealed moisture barrier material.
Problems w. refrigeration & freezing F & V
-Chilling injury -dehydration/transpiration
Benefits of continual air circulation in storage room
-Consistent temperature -Minimizes growth of modl
Procedures of harvest to ensure high quality
-Harvest previous to maturity > ripen at maximum rate just before full ripening -cooling fresh produce in the field, canned close to field
Primary precooling methods for fruits and vegetables
-Hydrocooling -Forced-air cooling -Package icing -Vacuum cooling
Pros and Cons of Frozen juices
-Maintains fresh character -costly -deterioration of nutrients, changes in flavor, color, viscosity,
Growing trends in beverages
-Organic ingredients -Without high fructose corn syrup (HFCS)
What do fruits and veggies continue to do during storage
-Respire -Generate heat
Misconceptions about preservatives
-Some are naturally existing -"no preservatives added does not equate to better product"
Processing methods used to preserve fruits and vegetables
-freezing -canning -dehydrating -pickling
Optimum storage temperature of most fruits and vegetables
0.5-1 degrees celsius above freezing point
Temperature swings of __________ from desired temperature must be avoided to maintain high quality and product consistency?
1 degrees celsius above or below
Two major types of operations
1. Canning 2. Freezing
2 processes for juices
1. Good sanitation 2. Low temperature holding
Two methods to manufacture jelly
1. Open kettle 2. Low calorie
Moisture loss can be minimized by
1. keeping storage temperature of food as lwo as possible 2. relative humidity as high as possible 3. avoiding high air velocities
Freezing
3 stages 1. Cooling to the freezing point - removing the sensible heat 2. Freezing - removing the latent heat 3. Further cooling to subfreezing - removes sensible heat of frozen food
Recommended refrigeration temperature for perishable foods
33.8 - 39.2
Standard jelly/jam manufacture requires a minimum of what percentage of weight fruit juice, pump or pieces
45%
Which fruits are commonly cut into smaller cubes/slice prior to freezing
Banana, tomato, mango, kiwi
Which preservatives are added to extend shelf life of minimally processed juice drinks
Benzoates + sorbates
When does enzymatic activity happen?
Between maturity and ripening
Solanine
Bitter, toxic at high levels; seen in onions, potatoesD
Dry pack method for freezing veggies
Blanched & drained vegs > meal-size freezer bags -packed tightly to reduce air -head space (2cm)
CO2 and O2 manipulation are used in what form of control?
CAP - Controlled Atmosphere Packaging MAP - Modified Atmosphere Packaging
What accounts for about 45% of industry revenue?
Canned and frozen foods
What are used to inactivate deteriorate enzymes in fruit
Chemical treatments/additives
Tray Packed Frozen Veggies
Chilled, well-drained veggies in single layer on shallow trays/pans -freezer until firm > removed -filled into containers; remain loose
Precooling
Cooling at the field before the product is shipped to the market or storage warehouse -most important for highly perishable products
Referigeration
Cooling w/o any phase change
Package icing
Crushed ice in containers (fruits)
Low calorie jelly
Difficult to manufacture and store. Susceptible to process contamination and refrigeration after opening
2 Types of packaging for frozen veggies
Dry pack Tray packed
Why does the green color of solanine changes?
Due to chlorophyll degradation > allow carotenoid pigment to be visible (green > yellow > orange >red)
Most common quality defects of fruit wines are
Excessive sweetness Oxidized flavor and color
Blanching
Expose veg. to boiling water/steam for brief period of time to inactivate enzymes -mild heat treatment -mainly for veg.
T or F, most foods freeze at a single temperature
False, range of temperature
T or F, blanching produces a sterile product
False, some microbes are still present; need further treatment to extend shelf life
Astronaut foods are usually
Freeze driedPa
Most expensive dehydration method
Freeze-drying; especially nitrogen gas
Beverages in trend right now
Fruit juices & 100% fruit-puree
What is the simplest fruit dry product?
Fruit leather/fruit rolls; low dextrose added to reduce hygroscopic nature > chewiness ~12% moisture content
Why would freezing fruits be different from freezing veggies?
Fruits are not fibrous -Delicate flavors easily damaged/altered by ehat -best eaten raw -attractive color
What level of maturity are fruits to be frozen at?
Fully ripe & soft in texture
Evidence of ripening
Green chlorophyll pigment - Solanine
Grapes
Harvested after completely ripened; over ripening cause stem detachment and decay; susceptible to moisture loss because of large surface area to volume ratio
Latent heat
Heat required to change form solid to liquid or liquid to gas, at constant temperature
Sensible heat
Heat when added or removed from foods, changes the temperature of foods
Which exceptions don't go through blanching
Herbs Green peppers
Chilling injury
Internal discoloration, soft scald, skin blemishes, soggy breakdown, failure to ripen -severity = temperature + time
Major US based fruits and veggies processing companies
Kraft Heinz JR Simplot Pinnacle Foods ConAgra General Mills
Which type of vegetables are extremely susceptible to presence of ethylene gas?
Lettuce, leafy vegetables
Pears
Loses moisture faster; stored under humid conditions
Transpiration
Loss of moisture from fresh fruits and veggies specifically -causes shrivel/wrinkle/lose quality (sold at lower price) -Varies based on environmental conditions and individual fruits
Does temperature play a role in dry products
Low temperature serves to extend shelf life
Dehydration
Moisture loss
Vinegar fermentation vs. wine making
More difficult to initiate and control
Ethylene Gas & Ripening
Naturally occurring colorless, odorless hydrocarbon in some fruits and vegetables (apples, bananas, citrus fruit, melon, tomatoes) -Generates softening of plant cell wall
T or F, refrigeration, pasteurization, and hermetic packaging increases storage w. minimum quality and changes is still considered fresh
No longer considered fresh
How are freeze-dried juice packaged?
Packaged in pouch of oxygen and moisture impermeable for rehydration. Rehydrated w. water generated from fuel cell reaction of hydrogen adn water
What level of maturity vegetables do manufacturers use for frozen veggies
Peak flavor and texture
Open kettle jelly manufacture
Professional HIgh quality: fruit, sugar, pectin -Immediate hot filling into sanitized jars -Rapid cooling -Low temperature storage
Factors to consider in packaging frozen veg.
Protection from O2 Moisture loss retention of flavor rate of heat transfer
Quality of frozen foods is greatly affected by...
Rate of freezing
Velocity of refrigerated air affects
Rate of moisture loss from products
Effect of evaporation on drying fruit juices
Reduce drying temperature and enhance quality
Climacteric Fruits
Ripen after harvest -Apples -Apricots -Avocado -Banana -Peach -Pear -Plum -Tomato -Papaya -Mango
Non-Climacteric Fruits
Ripen prior to harvest -Cherry -Citrus Fruit -Grapes -Melon -Pineapple -Strawberry
Frozen juices are produced via which processes?
Single strength juice freezing & low oxygen storage
The effects of refrigeration
Slows down chemical and biological processes in food (deterioration & loss of quality & nutrients) -extends shelf life
Benefits of blanching
Slows or stops enzyme action Easier to pack Some bacteria destroyed Surface dirt removed
Ripening can be done through
Sunlight, artificial, or fluorescent light
What process is capable of doing away the need of refrigeration and inactivate enzyme
Thermal processing
Why do fresh fruits and vegetables continue to give off heat even after they are picked?
They are live products
Major processed crops
Tomatoes Potatoes Oranges Corn Cucumbers Beans Grapefruit Apples Grapes Pineapples Peaches
Freshness, crispiness, and water retention in fruits and vegetables are attributed to
Turgor pressor
Turgor Pressure
Vacuoles in cells filled w. water; pressure is exerted on the cytoplasm and partially elastic cell wall
vacuum cooling
Vaporizing water content of products under low pressure conditions
When would headspace be unnecessary when packing freezing vegetables?
Vegetables that don't pack tight to begin with. Ex. broccoli, asparagus, brussel sprouts
Why do fruits and vegetables lose turgor pressure after picked?
Water lost to air w. evaporation or low humidity storage
Are fruits that require peeling peeled previous to freezing?
Yes, by scalding fruit in hot water/steam/hot lye solutions
Most produce can be stored satisfactorily at what temperatures and relative humidity
Zero degrees Celsius and 90-95% relative humidity
Gibberellic acid
control to external storage environment applied preharvest to delay ripening and retain firmness
Forced-air cooling
forcing refrigerated air (flowers)
Hydro-cooling
immersed in to chilled water (w or w/o chlorine)
100% fruit juice-puree mixtures
smoothies w. 100% fruit content