Food Biotechnology Dr. Kamal E. M. Elkahlout Fruits and Vegetables

1. Food BiotechnologyDr. Kamal E. M. ElkahloutFruits and Vegetables

2. Classification: Botanically – parts of the plants Fruits: various combinations of tissues that may include an expanded ovary, the seed, and other parts such as the receptacle (apple, strawberry), bract and peduncle (pineapple) Vegetables: Do not specifically represent any specific botanical groupings, thus exhibit a wide variety of plant structures

3. Compositions: Fruits • Water-varies from 75-90% has soluble substances like salts, sugars organic acids water soluble pigments and vitamins. • Carbohydrates-include sugars & starches as well as cellulose, hemicellulose and pectic substances • Proteins-low in protein • Fat-low in fruits except avocados and olives • Minerals-low in Ca,P &Fe • Vitamins-most fruits are low in B vitamins. Most fruits are excellent sources of vit. C Yellow/orange fruits eg pawpaw, mango are good sources of vit. A. Orange is good source of folate. • Organic acids-contribute to the taste of fruits eg citric acid-in citrus fruits, tomatoes, pineapple, malic acid in grapes, apples, pineapple

4. Ripening: A chemical process that changes the physical and chemical compositions and characteristics of fruits: Texture – from hard to soft Colour- green to pink, yellow, red, violet, etc (more appealing) Flavour-sour to sweet Less edible to more edible Aroma- no aroma to sweet smell, etc Stages of a plant’s life that are influence by hormone ethelene (gas created by plants from methionine AA. Fruits- differ depending on variety and ripeness

5. Ripening

6. Composition :vegetables • Most veg are good sources of CHO. • Fibre-veg are better source of fibre than fruits • Minerals- thin, dark green leafy veg are high in Fe,Green leaves of goosefoot family are good sources of Ca.However oxalic acid present in spinach binds Ca in an insoluble form. • Vitamins-Dark green veg are good sources of riboflavin, vitamin C and carotene (vitamin A) • Veg are also good sources of thiamine. • Organic acids-veg contain a number of organic acids however the content is lower in veg than fruits. tomatoes has highest con. of acids

7. Managing vegetables after harvest • Fresh fruits and vegetables: • living tissues • continue to breathe • composition and physiology continue to change after harvest • continue to ripen and, finally, they begin to die • cellular breakdown and death (senescence) are inevitable, slowed with optimal storage conditions • need low temperatures (32 to 55°F or 0 to 13 0C) and high relative humidity's (80 to 95 percent) to lower respiration and to slow metabolic and transpiration rates By slowing these processes, water loss is reduced and food value, quality and energy reserves are maintained.

8. Storage of fruits and vegetables • Once a crop is harvested, almost impossible to improve its quality. • Loss from improper storage and handling can range from 10 to 40 percent. • Bruises in fruits rich in phenolics cause undesirable discolouration called enzymatic browning (undesirable browning): • Enzyme responsible for enzymatic browning, ortho-diphenol: • oxygen oxidoreductase, is also known as • catecholase, tyrosinase, phenolase, and polyphenoloxidase.

9. Storage temperature • Proper storage conditions—temperature and humidity needed to lengthen storage life and maintain quality once the crop has been cooled to the optimum storage temperature. • Each fruit or vegetable has its own ideal set of conditions at which it will store most successfully for a max length of time.

10. Storage temperature • Some fruits and vegetables should be stored only at room temperature due to damage by low tempt (3.3-5.6 0C) e.g. banana. • While other fruits need to be stored in the refrigerator to maintain in quality and to prevent the loss of vitamins eg vit C

11. Cooking or Heating • destroys enzymes and micro-organisms • reduces bonds on the pectin molecules, making more sites available for cross-bonding thus • increase firmness in some fruits e.g. potato pectin methyl esterase (PME) is active at 50-700C • PME -catalyses removal of methyl grps from pectin molecules which increase the no. free COOH. • intracellular ions e.g. ca & mg come in contact and react with cell wall components e.g. free COOH forming bridges that strengthens the tissue: • this helps resist degradation during heating

12. Blanching • is heating in water or steam for a short time and then cooled on trays • destroys enzymes and prevents changes in colour, flavour and texture during storage but does not preserve the food and vegetables • to be further processed by drying to achieve a longer shelf life • steam blanching retains more nutrients (water soluble nutrients not lost into the water) compared to water blanching.

13. Treatments NaHCO3(baking soda) • Added to blancher water retains colour or brighten green colour of leafy vegetables, peas etc. CaCl2 • Firming agent in fruits and vegetables which acts on pectin, which exists as a firm gel around fibrous tissues and prevents their collapse. • During food processing, CaCl2 (ions) forms a calcium pectate gel that strengthens the pectin complex, increasing firmness and crispness. • Thus there is greater support for tissues helps protect against softening during processing.

14. Sulphuring • For most fruits, 350-400g sulphur are used per 100 kg fruit, burning for 1-3 hours. • Sulphur dioxide prevents browning in foods such as apple, banana and coconut (should not be used with red fruits as it bleaches the colour). • Sulphuring (gas) is achieved by exposing pieces of cut or shredded fruits to burning sulphur in a sulphuring cabinet. • Amount of sulphur used and the time of exposure depend on the type of fruit, its moisture content and limits placed by law in some countries on the residual amounts of sulphur dioxide in the final product or by commercial limits set by importers

15. Sulphiting • In sulphiting, the sulphur dioxide is dissolved in water • Sodium sulphite, sodium metabisulphite or potassium metabisulphite are made into solutions, either by adding one of them to the blanching water or more often, by soaking the food for 5-10 minutes in a sulphite dip.

16. Canning or bottling Vegetables and fruits can be canned/bottled in syrup, brine or acid. Acidic fruits require mild heat treatment for pastuerisation while less acidic fruits require severe heat sterilazation to destroy food poisoning bacteria, yeasts and molds Time and temperature of canning are critically important and must be carefully controlled. under-processed cans pose a risk of serious food poisoning and even death from a type of micro-organism named Clostridium botulinum. over-processed cans of vegetables lose much of their texture, colour, vitamins and flavour and are not saleable.

17. Frying • Starchy fruits, including jackfruit, breadfruit and banana are fried and eaten as snack foods. • Heat during frying removes moisture from the food, destroys microorganisms and increases shelf of the product. E.g potato chips • However : • very hot oil can splash onto operators when wet fruit is immersed

18. Frying • When oil is heated too much, it exceeds its smoke point and a blue haze appears above the oil. • a sign of oil breaking down chemically and it will then begin to get more viscous and develop an unpleasant flavour. • flavour is transferred to the product, making it unacceptable. • When the oil thickens, more is retained on the product and there is a higher cost in buying more oil than is needed. Too much oil on the product also reduces its shelf life.

19. Dry heat Drying removes most of the water from fruits and vegetables to extend their shelf life and to increase their convenience and value. Air dry Air dried products are the most common type of dried fruit and vegetables. Freeze drying (expensive method) may be used. Before preserving products may be blanched/sulfited to preserve the natural color of fruits and veg.

20. Salt and drying • The high salt concentration preserves the food by both drawing out water by osmosis and by the anti-microbial properties of the salt. High salt con. • Also prevent the action of enzymes thus preventing loss of quality of fruits/veg. Veg are usually washed to remove the salt before they are eaten.