Fruit And Vegetable Processing

Question 1

Fruits are grouped into seven divisions

Answer 1

1. Berries - generally small and fragile, eg. blueberry
2. Melons - large with tough rind eg. Cantaloupe
3. Drupes - contain single pit eg. Cherries and peaches
4. Pomes - contain many seeds eg. Apple and pears
5. Citrus
6. Tropical - require warm temps eg. Pineapple

Question 2

Respiration of fruits and veg

Answer 2

Fruits and Veg continue to respire after being picked, giving off carbon dioxide, water and heat while uptaking Oxygen.
Aerobic respiration - we want to slow it down but not stop it completely.
Respiration : sugar and oxygen are converted into carbon dioxide and water and energy in the form of heat.
Fruit retains 90% of its energy as heat which can lead to spoilage

Question 3

What is Transpiration

Answer 3

Involves loss of water vapour.

Water, sugars, mineral reserves with fruiting bodies are depleted over time

Question 4

What are the three major life stages of fruit and veg?

Answer 4

1. Growth
2. Maturation
3. Senescence - involves a change from anabolism to catabolism
   1& 2 =s the development stage
   Ripening happens at the end of the maturation and first stage of senescence (happens on or off plant)

Question 5

Physiology of fruit respiration

Answer 5

Respiration means an increased evolution of carbon dioxide or a decrease in internal oxygen.
It is the metabolic opposite of photosynthesis
Aerobic respiration = sugar+oxygen taken in and carbon dioxide, water, and energy out.

Question 6

What are Climatric and Non-Climatric fruits?

Answer 6

Climatric Fruits- respire at a peak near the end of the maturation phase. Eg. Banana, pear, Apple, avocado. They also produce more Ethylene (ripening hormone) than non

Non- Climatric Fruits - have no respiratory peak eg. Pineapple, cherry, strawberry, blueberry and citrus.

Question 7

Effect of Ethylene

Answer 7

Is a hormone used to regulate ripening.
Can be applied to climacterics to stimulate the onset of ripening. Eg. Bananas
Can also be used to hasten the ripening like changes of non- climacterics

Question 8

Responses to Temperature

Answer 8

Lower temps reduce the rate of ethylene production, retard microbial growth, and reduce transportation.
But some crops are susceptible to ‘chill injury’
For starchy veg like potatoes there is a ‘critical temp’ below which sugar accumulates
The increase of temp also increases respiration
Which is why the refrigeration system must lower temp and remove heat of respiration
In starchy foods - like corn and potatoes, the conversion of sugar to starch increases with temp and time of storage.

Question 9

Chilling applications and procedures

Answer 9

Pre-cooling - administered prior to storage or shipping, quickly removes heat at time of harvest.
Chill injury - result of Low temp. Manifests as a breakdown of flesh, growing, mould growth, rotting. Failure to ripen normally after storage.
Depends on storage temp, time, state of tissue ( maturity and composition), storage atmosphere, and rate of water loss.

Question 10

Controlled Atmosphere Storage

Answer 10

Extends the preservation effect of ordinary cold storage. Decreased oxygen and increased carbon dioxide which down ripening and related physiological disorders. May also control ethylene levels.
Too little oxygen results in fermentation wile too much carbon dioxide can have same effect
Controlled atmosphere storage can result on firmer texture with lower pectic enzyme activity.

Question 11

Controlled atmosphere vs modified atmosphere

Answer 11

Controlled atmosphere - precise control of oxygen and carbon dioxide levels in a facility designed for this purpose. which down ripening and related physiological disorders

Modified atmosphere (packaging) - usually refers to packaged products which have been flushed with a gas mixture which will chAnge with time, unlike CA storage. Usually involves mixtures of CO2, O2, and Nitrogen.

Question 12

Modified Atmosphere Packaging - what are the gases used and what do they do?

Answer 12

CO2 - inhibits bacterial and mould growth and is absorbed into the water in food, thus lowering ph.
N2 - is chemically inert and thus retard oxidation reactions as well as mould growth
O2 - is used to inhibit growth of anaerobes but can accelerate oxidative rancid its
Gas impermeable packaging can promote bacteria growth

Question 13

What are the general unit operations of Fruit Juice Production?

Answer 13

1. Extraction of juice
2. Clarification
3. Deaeration -minimizes oxidative changes (eg. Destruction of vit C)
4. Pasteurization - inactivates enzymes , destroys vegetative microbes
5. Concentration
6. Freezing

Question 14

Apple Juice Production

Answer 14

Step 1 - fruit handling and juice extraction 
Washing
Milling
Placed in holding tank and Adding enzymes (pectinase which removes solvable and insoluble pectin)
Incubation for 15 mins to 2 hrs
Pressing - to produce cloudy juice 
Step 2 - aroma recovery
Evaporation
Distillation
Step 3 - clarification 
Depectinization /enzyme treatment
Cooling
Floculation
Filtration = clarified juice
Step 4 - concentration
Evaporation

Question 15

Clarification of Apple Juice

Answer 15

Haze is due to suspended particles which can be proteins or cell fragments.
Another haze problem is sometimes developed over storage time of clarified juice.
Haze may be due to soluble pectins
Protein (+) with a pectin coating (-) will repulse each other and and therefore will continue to float around in haze, but partially remove the pectin coating to expose the positively charged protein and you get attraction and aggregation so the particles will be large enough to float to the bottom and can the be filtered out