Fruit Processing Industry- An Insight

What is Fruit and Fruit processing?

Fruits are a high-moisture, generally acidic food that is relatively easy to process and that offers a variety of flavor, aroma, color, and texture to the diet.

Food processing aims to make food more marketable and attractive to potential consumers, often giving the processed food a longer shelf-life. Fruit can go through numerous types of processing, including canning, drying, and juicing. Some types of processed fruit are fruit preserves, canned fruit, and fruit juices. Processed fruit is generally not as healthy as fresh, raw fruit.

Washing, drying, and packaging fruit is usually not considered processing. Processing begins when the fruit is turned into something other than raw fruit by cooking or preserving it. Even if this process is as simple as cutting an apple and drying it to preserve it, that apple is no longer raw fruit. Sometimes additives, preservatives, and sugar is added to processed fruit to make it look and taste better than it normally would when a customer finally opens the product to consume it.

After fruit is washed multiple times, the processing begins. As an example, if the fruit is to be turned into fruit preserves, it is first cooked until soft. A sugary syrup and sometimes additives and preservatives are added. The fruit is then sealed into a jar, or in some cases, placed in a squeeze bottle. As another example, the fruit is dried and packaged, sometimes with sugar added depending on how sweet the fruit is naturally. 

Methods of Processing:

Processing of fruits and vegetables is very important to produce products for direct consumption and as food ingredients.

There are three major processes,

1. Canning
2. Freezing
3. Drying

1. Canning

Canning is defined as preservation of foods in hermetically sealed containers and usually implies heat treatment as the principal factor in prevention of spoilage. Canning was invented by Nicholas Appert in 1910 so also termed as Appertization.

Foods that are canned

• Low acid foods: Meat, fish, poultry, dairy fall into a pH range of 5.0 to 6.8. This large group is commonly referred to as the low acid group.
• Acid foods: With pH values between 4.5 and 3.7. Fruits such as pear, oranges, apricots and tomatoes fall in this class.
• High acid foods: Such as pickled products and fermented foods. The pH values range from 3.7 down to 2.3, also Jams and Jellies are in this classification.

 

1.1. Principle of canning:

Destruction of spoilage microorganism within a container by means of heat. Preserving using a canning method involves placing food in specified canning jars that are sealed with two-piece lids. The jars are heated to a temperature that destroys harmful microorganisms and inactivates enzymes. This heating, and later cooling, forms a vacuum seal. This vacuum seal prevents further microorganisms from entering the jar and contaminating the foods during storage.

1.2 Canning Process flow chart:

 

2. Freezing

Freezing is a low temperature preservation process where the product is frozen at -38 0C and stored -18 0C. Freezing is cheaper than canning and frozen products are close to fresh products and of better quality the metabolic activity and spoilage due to post harvest chemical are retarded by freezing. Through the product preserved by freezing retains their quality appreciably, the major disadvantage of the process is that the low temperature has been maintained during handling, transportation and storage before the product is finally consumed. Suitable fruits and vegetables for freezing are mango slices, pulp, pineapple slices, guava slices, orange segments, peas, carrot, cauliflower, beans, etc.

IQF refers to Individual Quick Freezing of every particle/aggregate using fluidization in a stream of very cold air. Fluidization leads to high heat transfer co-efficient and therefore very rapid freezing and hence better quality. For example, freezing of green peas in an air blast freezer may take 3-4 h whereas it is only 10-12 min by IQF. This results in for better texture and there is no humb or block formation. Some of other important IQF products are frozen fruit dices and cut vegetables.

• Easy, convenient and the least time consuming
• Slows growth of microorganisms and chemical changes
• Preserves the greatest quantity of nutrients

 2.1 Equipments of freezing

1) Freezer/cold room

2) Quick freezing Equipments- fluidized bed freezer, automatic package freezer, continuous plate freezer, continuous can freezer

3) Direct Immersion equipments- Brine Freezer, Frog freezer, and Bartlett freezer

4) Rotating cold drum

5) Foot operated polythene bag sealer- sealing polyethylene bags of different gauges after filling of fruits and vegetables

2.2 Methods of freezing

 i) Quick (0 to -40 0C for 30 min.)

ii) Sharp (-15 to -29 0C for 3-72 h)

iii) Cryogenic (-196 0C)

iv) Dehydro-freeing (50 % moisture removed)

2.3 Freezing Process Flow chart

 

 

2.4 Freezing Overview

• Frozen in many forms – Whole, sliced, crushed, juiced etc.
• Best quality- choose fully ripe, but firm, fruit – Immature or overripe produce lower quality when frozen

2.5 Types of Packs; – Syrup pack, Sugar pack, Dry pack, Unsweetened and water packs.

2.6 Storage Times

Fruits – Most frozen fruits maintain high quality for 8 to 12 months – Unsweetened fruits lose quality faster than fruits packed in sugar or sugar syrups.

2.7 Summary

• Freezing fruits and vegetables is a safe, easy way to preserve foods
• Wash all fruits and vegetables thoroughly
• Follow blanching charts for vegetables
• Use proper procedures and equipment, including freezer-safe materials • Use the freezing process that works best for your family meal needs

3. Drying method:

One of the oldest methods of preserving food and its alternative to canning & freezing. It is Simple, safe and easy to learn , In this no refrigeration needed  and it takes little space . It removes moisture from food so bacteria, yeasts & molds can’t grow and spoil food. It Slows down action of enzymes but doesn’t inactivate them.

 3.1  Factors

• Surface area – The greater the faster the product dries
• Temperature – The greater the difference between the product and drying medium, the greater the rate of drying
• Humidity – The higher, the slower the drying
• Atmospheric pressure – The lower, the lower the temperature required to remove water.

3.2 Binding of Water

As a product dries, its free and water is removed .This water evaporates first,Water in colloidal gels, such as starch, pectin or other gums is more difficult to remove. Water that is most difficult to remove is that chemically bound in the form of hydrates.

3.3 Methods of Drying

• Sun drying: in Dry, warm climates
• Spray drying – Tray (air) drying
• Tunnel drying – The tunnel dryer is a machine where a container (tray) filled with the material is placed on a trolley or the material is loaded directly on the trolley, and the trolley is pushed in from the tunnel chamber entrance. The material is dried while being moved through the drying chamber.

4. Dehydration

 Dehydration is the removal of moisture from fruits and vegetables by artificially produced heat under controlled condition of temperature, relative humidity and air flow. In dehydration, sufficient moisture is removed so that the product is free from spoilage; but this must be done in such a way to preserve food value as far as possible. Rate of dehydration is so done in hygienic condition to have products of uniform colour than sun dried. Dehydration reduces the bulk, requires less storage space and usually cheaper that the other methods of preservation. The suitable fruits and vegetables for dehydration are grape, date, fig, raw mango, anola, ber, litchi, apricot, banana, apple, carrot, leafy vegetables, etc. FPO specification for dehydrated fruits and vegetables are;

1) Moisture content shall not exceed 20 per cent and 24 per cent (w/w) respectively.

2) Fruits and vegetables used for drying be clean, wholesome and shall be practically free from insect or fungal attack.

3) Dehydrated products may contain permitted preservations. 

4.1 Equipments used for Dehydration

 Blanching unit:  It can be used for pre-treatment (steam blanching) of fruits and vegetables before processing.

 Types of dryers used: Kiln drier- pieces; Cabinet/tray drier- pieces; purees, liquids; tunnel- pieces; continuous conveyer belt-purees, liquids; Belt trough-pieces; air lift- granules; spray- liquid; vacuum-purees, liquid, pieces; Fluidized bed-small pieces; Drum or roller-Liquid, purees.

 Vacuum drier- It is used for dehydration of fruits and vegetables without any change in sensory attributes.

4.2 Packaging requirements for dehydrated foods

• Protect against moisture absorption Dehydrated foods- hygroscopic Prevent transmission of water vapor
• Physical protection Prevents crushing Freeze dried foods- porous structures with spaces; easily crushed
• Protection from oxygen and light photo- oxidation

 

4.3 Dehydration Process Flow chart