Fruits and Vegetables Tech. lecture notes Page 9 of 12

FRUITS AND VEGETABLES TECHNOLOGY

Introduction

Fruits and vegetables, which are among the perishable commodities, are important ingredients in the human dietaries. They offer the most rapid and lowest cost method of providing adequate supplies of vitamins, minerals, and fibre to people.

Fruits and vegetables are available as seasonal surpluses during certain parts of the year in different regions and are wasted in large quantities due to absence of facilities and know-how for proper handling, distribution, marketing and storage. Neither can they all be consumed in fresh condition nor sold at economically viable prices. If they can be supplied in fresh or preserved form throughout the year for human consumption, the national picture will improve greatly. It is therefore important to explore technological ways of alleviating losses in fruits and vegetables.

Classification of fruits and vegetables

Tropical fruits and vegetables

In the tropics, vegetables are understood to mean the leafy outgrowth of plants used as food, while in the temperate developed world, vegetables are served as accompaniment to the entrée, and fruits are served as appetisers and desserts.

Fruits Vegetables

Avocado Beans, peas (legumes) Squash

Banana Carrots Bread fruit

Date Cucumber

Pineapple Egg plant

Mango Lettuce

Guava Garlic

Pawpaw Onion

Orange Pepper

Grape fruit Okras

Lemon Tomatoes

Tangerine Spinach & other green leafy vegetables

Cashew apple Sweet corn

Passion Yams, potatoes, sweet potatoes

Soursop Coco yam

Pomarac Plantains

VEGETABLES

Vegetables can be divided into two major groups:

a)  Those whose edible parts are picked above the soil, e.g. mushroom, cauliflower, peas, celery, rhubarb, blackjack, okra, and pumpkin.

b)  Those whose edible parts are pulled or dug from the soil e.g. carrots, onions, beetroots, sweet potatoes, potatoes and yam.

A second way of classifying vegetables is according to what is eaten: leaves, roots, flowers or fruits. Complete notes from pp 161-165 (Malaba, 1988)

a)  Leafy vegetables – cabbage, rape

b)  Fruit vegetables – green pepper, marrow

c)  Tubers and roots – Tsenza/ umuhlaza, radishes

d)  Bulbs – shallots, onions, and garlic

e)  Flower vegetables – cauliflower, broccoli, pumpkin flower.

STORAGE AND PRESERVATION

A cool atmosphere, near but not below freezing point, and sufficiently high freezing point, and sufficiently high relative humidity to prevent drying out. Adequate ventilation is also necessary.

The table below gives the general techniques for storage and preservation of vegetables

Controlled environment / Heat treatment / Dehydration and related methods / Other methods
Controlled atmosphere storage / Blanching / Sun drying / Sugar
Reduced temperature
·  Chilling
·  Freezing
·  Newer cryogenic techniques / Pasteurisation / Dehydration by various methods including new advanced techniques, e.g. freeze drying / Salt
Packaging / Bottling, Glass,
Canning / Concentration / Chemical
Fermentation
Irradiation

Ihekoronye & Ngoddy (1985 p. 295)

The controlled environment, heat treatment, dehydration, and related methods are used in vegetable preservation. For longer-term storage, refrigeration is the best method for maintaining quality. Green leafy vegetables can be kept successfully for a week at about 5 – 100 C. at a relative humidity of more than 800 C. However, sun drying better preserves some vegetables such as pepper, onions, bitter leaf, and okra. This method helps to concentrate the proteins, though some nutrients are destroyed. Fermentation on the other hand improves the levels of protein, minerals and vitamins in vegetables.

Classification of fruits

Fruits are similar in composition to vegetables. To some extent, they have laxative effect. Fruits can be classified as discussed in the following pages.

There are:

·  Deciduous fruit trees – lose leaves in winter: peaches, apples, plums, apricots, grapes, and pears.

·  Subtropical fruits – grow in a climate, which is neither too hot nor too cold e.g. bananas, pineapples, mangoes, pawpaw, and avocado pears.

·  Citrus fruits – covered by rind, inside consists of segments, e.g. oranges, lemons, lime, grape fruit and naartjies (mandarins).

·  Other fruits – inside is embedded with many tiny seeds. E.g. strawberries, blackberries, gooseberries, and guavas.

In Zimbabwe, according to Malaba (1988), there are indigenous fruits that grow in the veld, and can be classified as follows:

1. Deciduous fruits

a)  Chocolate berry – chikumai/ umbalebale from coffee bean tree

b)  Quarters/ monkey bread – matohwe/ uxakuxaku

c)  Monkey apple – mazhumwi/ umhlali, yellow in colour than the orange

d)  Wild orange – matamba/ amakhemeswane has many seeds in the pulp. Pulp can be used to make a drink or sour porridge.

e)  Wild plum – munhunguru, very common in plumtree area

f)  Mazhanje – amahobohobo – has several seeds & has a pleasant taste.

g)  Marula – mapfura/ amaganu, seeds have high percentage protein and fat content.

2. Other fruits

a)  Baobab – mauyu/ umkhomo

b)  Live long – mashamba/ isigangatsha, when ripe, it is purple black in colour

c)  Prickly pear – dhorofiya/ idolofiya, succulent plant which, can withstand any hard conditions

3. Fruits from trees with evergreen leaves

a)  Sand apple – mahacha/ umkhuna, flesh can be made into porridge. Delicious syrup can be prepared from the pulp, mixed with water and then boiled down to the syrup. Kernels can be chopped and added to a vegetable relish.

b)  Sour plum nhengeni/ umthunduluka, is sour

c)  Wild gig – green, but changes to reddish colour when ripe. The fruit is used to make jam.

TOPIC 2. FOOD ADDITIVES

Definition

A food additive is a substance or mixture of substances, other than a basic foodstuff, which is present in a food as a result of any aspect of production, processing, storage, or packaging.

Can also be defined, as non-nutritive substance added intentionally to food, generally is small quantities, to improve its appearance, flavour, texture, or storage properties. This definition left out minerals and vitamins – quality purposes.

Functions & uses

They are many and include:

Drying, emulsifying, enhancing flavour, enriching, flavouring, foam producing, glazing, leavening, lining food containers, maturing (flavour), anticaking, antidrying, antifoaming, antihardening, antispattering, antisticking, bleaching, buffering, chillproofing, clarifying, colour retaining, colouring, conditioning (dough), creaming, curing, dispersing, dissolving, sweetening, texturising, thickening, water-proofing, water-retaining, whipping, acidying, making alkaline, neutralising, peeling, plasticising, preserving (including acting as antioxidant), pressure dispensing, refining, replacing air in food packages, sequestering unwanted metal ions, stabilizing, sterilizing and supplementing nutrients.

Major uses

1.  Enhancement of the attractiveness of foods by means of colouring and flavouring agents, emulsifiers, stabilisers, thickeners clarifiers and bleaching agents,

2.  Maintenance of nutritional quality, such as by the use of antioxidants

3.  Facilitating food processing by means of acids, alkalies, buffers, sequestrants, and various other chemicals, and

4.  Enhancement of keeping quality or stability by the use of antioxidants, antimicrobial agents, inert gases, meat curers, etc.

Classification

  1. Antioxidants – when added to fats and fat-containing foods, they prevents their oxidation and thus prolongs their shelf-life, wholesomeness and palatability. E.g. Butylated hydroxyanisole (BHA); butylated hydroxytoluene (BHT); tertiary – butylhdroquinone (TBHQ); propylgallate (PG); sulphurdioxide; ascorbic acid (prevents browning by oxidation of phenolic compounds.)
  2. Preservatives – substances capable of inhibiting, retarding or arresting the growth of microorganisms. May be chemical or natural (sugar, salt, acid). E.g. sulphur dioxide & sodium benzoate, sodium and calcium propionate (as mould inhibitor in bread & cake), sorbic acid as mould and yeast inhibitor in cheese and baked products, fruits juices, wines and pickles) and chlorine compounds (germicidal wash for fruits and vegetables) are also used as preservatives.
  3. Sequestrants = chelating agents or metal scavengers. They combine with metals such as iron and remove them from the solution. Traces of metals catalyse oxidation and also cause discolouration, rancidity, turbidity and flavour changes in foods and must be removed by chelating agents such as polyphosphates or citric acid. Calcium and sodium salts of organic acids, calcium chloride, calcium phosphate, tartaric acid, and citric acid, are other examples. For example, in soft drink manufacture, iron in the water reacts with the one of the flavouring substances to form an insoluble compound that makes product cloudy. Citrates form a soluble complex with iron, whereas others render citric acid insoluble.
  4. Surface active agents – known as emulsifiers and are used to stabilise oil –in- water, water -in -oil, gas- in -liquid, and gas- in- solid emulsions. E.g. Natural – lecithin; synthetic – mono and diglycerides, and derivatives.
  5. Colouring agents make attractive & appetizing. Natural – e.g. extract of annatto, caramel, carotene and saffron, or synthetic which are superior in colour power, uniformity and stability of colour and are cheaper. Carbon black imparts blackness; titanium dioxide intensifies whiteness.
  6. Buffers, acids and alkalies – control or adjust the pH of foods and affect properties such as flavour, texture and cooking qualities. E.g. acetic acid, ammonium carbonate, ammonium hydroxide, calcium carbonate, calcium chloride, calcium citrate, citric acid, lactic acid, malic acide, sodium acetate, sodium bicarbonate, succinic acid, tartaric acid, sulphuric acid, sodium hydroxide, etc.
  7. Stabilizers and thickeners – improve texture of foods, inhibit crystallization of sugar and formation of ice, stabilise emulsions and foams and reduce stickiness of icings on baked products. E.g. agar-agar, alginic acid, gelatine, pectin, amylose, gravies, pie fillings, jellies, puddings and salad dressings.
  8. Nutrient supplements – mainly vitamins and minerals: vitamin A, C, D, B, Iron, Calcium, Iodine.
  9. Non-nutritive and special dietary sweeteners – used in manufacture of low-calorie soft drinks. Sweeteners are 10 to 3000 times as sweet as sucrose. The 1st was saccharin, which is now prohibited. Aspartame is used in chewing gum and as dry base for beverages; neohespiridine, a dihydrochalcone isolated from citrus peel, is also a sweetener.
  10. Flavouring agents and flavour enhancers – it is the largest group of food additives and includes about 2100 different substances. E.g. amyl acetate (banana), methyl anthranilate (grapes) and ethyl butyrate (pineapple).
  11. Anticaking agents and humectants – absorb excess moisture, by coating the food particles to make them water repellent, and/ or by diluting the mixture with insoluble particles. E.g. calcium silicate in baking powder; calcium stearate in dehydrated vegetables, salt and other food ingredients in powdered form. Other anticaking agents are sodium silicoaluminate, tricalcium phosphate, magnesium silicate, magnesium carbonate, etc.
  12. Bleaching and maturing agents (flavour improvers) and starch modifiers – benzoyl peroxide is such an agent which bleaches the yellow colour. Oxidizing agents e.g. hydrogen peroxide are used to whiten the colour of milk for manufacture of certain kinds of cheese; bromate and iodate are used in bread dough for improving baking quality.
  13. Other additives

a)  Firming agents – keep tissues of fruits and vegetables crisp (firm), e.g. calcium chloride and aluminium sulfate

b)  Clarifying agents – remove haziness or sediment produced by oxidative deterioration in fruit juice, wines, beers, etc. e.g. bentonite, gelatin, synthetic resins (polyamides and polyvinylpyrrolidone).

c)  Solvents – suspended flavouring agents, dyes and other ingredients can be dissolved by adding solvents such as alcohol, acetone, hexane, propylene glycol, glycerine, etc.

d)  Antisticking agents –e.g. hydrogenated sperm oil

e)  Machinery lubricants e.g. mineral oil

f)  Meat curing agents e.g. sodium nitrite and sodium nitrate

g)  Crystallisation inhibitors .e.g oxystearin

h)  Growth stimulants – gibberellic acid used for malting barley.

i)  Leavening agents .e.g ammonium sulfphate – used in yeast foods to promote the growth of baker’s yeast.

j)  Freezing agents – e.g. liquid nitrogen for chilling foods

k)  Packaging gases – e.g. inert gases for preventing oxidative and other changes in foods

l)  Enzymes – e.g. rennin for producing cheese and curd, papain for tenderising meat, and pectinase for clarifying beverages.

SUBSTANCES PROHIBITED AS ADDITIVES – Code US Federal Regulations (1979)

·  Brominated vegetable oild (BVO)

·  Calamus and its derivatives

·  Chlorofluorocarbon propellants

·  Cobalt salts and derivatives

·  Coumarin and dihydrocoumarin

·  Cyclamate and its derivatives

·  Diethylpyrocarbonate (DEPC)

·  Dulcin

·  Monochloroacetic acid

·  Nordihydroguiaretic acid

·  Sofrole

·  Thiourea

·  Some colourants – e.g. acid magenta II; brilliant black; red FB; red 6B.

FOOD ADDITIVES TO BE USED WITH CAUTION

Additive / Use / Possible adverse effects
Coal tar dyes / Colourant in vegetable and fruit products, soft drinks, candy, desserts, pastry, sausage, baked food, ice-cream, hot dogs, hamburgers, sweetmeats, snacks, confectionary, alcohol and other beverages. / Allergic reactions, cancer and pathological lesions in vital organs.
Butylated hydroxytoluene (BHT) / Antioxidant in cereals, chewing gum, potato chips, edible oils, etc. / Cancer; allergic reactions; stored in body fat.
Butylated hydroxyanisole (BHA) / Antioxidant in cereals, chewing gum, potato chips, edible oils, etc. / Appears to be safer than BHT, but needs more testing.
Caffeine / Stimulant in soft drinks / Insomnia and other adverse effects at high levels of intake. Not recommended for children and pregnant mothers.
Saccharin / Non-calorie sweetener in food products, also as adulterant. / Bladder cancer reported in animals. Not recommended for normal people (not suffering from diabetes, obesity)
Sodium nitrite and nitrate / Preservative to prevent growth of bacillus, Clostridium botulinum and colourant for bacon, ham, meat, smoked fish, and corned beef. / Formation of small amounts of cancer-producing nitrosamines.
Artificial flavourings / In soft drinks, breakfast cereals, baked goods, vegetable and fruit products, ice creams, custards, desserts, alcoholic beverages. / Hyperactivity in some children; not adequately tested for safety.
Monosodium glutamate / Flavour enhancer for soup, poultry, meat preparations, sauces, stews and cheese. / Damages brain cells in infant mice, so not recommended for children; headache, tightness of head, neck and arms in sensitive adults (Chinese Restaurant Syndrome).
Sulphur dioxide and bisulphites / Preservative and bleach for sliced fruit, wine, grape juice, dried potatoes, dried fruit, vegetable and fruit products, etc. / Destroys vitamin B1, but otherwise safe at prescribed levels.
Phosphoric acid and phosphates / Acidifier, chelating agent, buffer, emulsifier, and nutrient, discolouration inhibitor used in baked goods, cheese, cured meat, soft drinks, and dried potatoes. / Dietary imbalance that may cause bone thinning (osteoporosis) on prolonged use.
Talc and Kaolin / Making dry powdery foods free-flowing and dusting agent for rice, confectionery, chewing gum. / Absorbed and stored in vital organs; cancer if asbestos is present.

PRESERVATION AND STORAGE OF FRUITS