Food & Technology

FRUITS

Origin

A fruit is the edible part of a plant that contains a seed or the matured ovary of a flower.

Fruits are defined botanically as “the matured ovaries of flowers”

Structure

Fruits have 3 sections – the skin, the flesh and the seeds.

Fruit comes in a wide variety of colours, textures and flavours and are generally sweet in taste.

Colour – due to various pigments. Green is due to chlorophyll

Orange & Yellow are due to carotenoids

Red & Blue due to anthocyanins

The Process of photosynthesis

The green pigment in plants (called chlorophyll) uses carbon dioxide in the atmosphere, energy from sunlight and water to produce carbohydrates for energy for growth. The carbohydrate is stored in the fruits we eat.

Pectin

This is a complex polysaccharide found in the cell walls of many fruits.

It forms a gel with sugar in acid conditions and is responsible for the setting of jams. It can be purchased commercially as Jamsetta or in Jam setting sugar.

Find images of jam, Jamsetta & jam setting sugar

Flavour

Different flavours in fruits are due to complex mixtures of naturally occurring chemicals.

They range from the subtle, slightly ‘perfumed’ flavour of a mango to the strong citrus flavour of a lemon.

The acids each fruit contains determines the flavour. Citric acid – oranges, lemons, grapefruit, limes Malic acid - apples, pears, peaches, apricots Oxalic acid - pineapples Tartaric acid – grapes

Sweetness - is due to the sugars fruits contain. Fruit sugar is called fructose and is a simple carbohydrate so provides quick, short bursts of energy.

Texture - formed from a combination of different properties – the plant cell shape and size, the amount of water in the fruit cells and the amount of

cellulose (fibre and starch) in the cells.

Nutrient content of fruit

Fresh fruit is manly composed of water and carbohydrates. Many are low in kilojoules.

The carbohydrate in ripe fruits is in the form of sugar such as sucrose, fructose & glucose

Some carbohydrate is also present in the form of cellulose, a polysaccharide. This is not easily digested and forms dietary fibre.

Fruit is a valuable source of vitamins and the main source of vitamin C

Vitamin A, in the form of carotene, is present in yellow and orange fruits. Some fruits contain small amounts of minerals, such as

phosphorus, potassium and calcium.

When fruits ripen:

Pigments underneath and in the skin of fruit break down, causing a colour change. An example is

where apples change colour.↓

The edible pulp surrounding the seed becomes soft and tender as the water content increases.

↓The starch present converts to sugar, causing the

flavour to become sweeter↓

A fuller and more distinctive aroma develops on ripening

Classification of fruits Fruits are grouped together in families according to how they grow & the physical properties of the fruit.

POME FRUIT Examples - Apple, pear, quince

PROPERTIES Physical - compartmented core that contains seeds. Core

surrounded by crisp, juicy flesh. Have an indentation in the core end of the fruit.

Chemical - Acids present – citric and malic. Apples are a good source of fibre & vitamin C Sensory – Apples – firm, crisp texture, sweet flavour Pears - soft, tender flesh, sweet flavour Storage - store apples in the refrigerator to keep them crisp. Keep

them away from green vegetables which are sensitive to a natural gas (ethylene) given off by the apples.

Classification of fruits

CITRUS FRUITSExamples – oranges, grapefruit, lemons, cumquats, limes, mandarins

PROPERTIESPhysical – Firm, thick, lightly dimpled skin present in most varieties. Colours range from green (limes) to orange (mandarin, orange) and yellow (grapefruit, lemon. Internally, made up of juicy flesh that separates into membrane covered segments.

Chemical - good source of vitamins (particularly Vit C) as well as minerals & dietary fibre. Citric acid present.

Sensory – flavour can range from acidic to tangy and reasonably sweet, depending on type of fruit. Storage – Store at room temperature for about 5 days when the weather is cool to mild but best to refrigerate in hot weather for extended storage time.

Classification of fruits

BERRIESExamples – strawberries, raspberries, loganberries, blackberries

PROPERTIESPhysical – Some (eg raspberries) are clusters of a number of small fruits, each tiny segment is a dupe or juice filled sac. With strawberries, what appear to be seeds on the surface are actually individual fruits (achenes) containing a single seed. Blueberries and cranberries are single fruits formed from the plant’s ovaries.

Chemical - Berries are good sources of Vitamin C, potassium, iron and fibre.

Sensory – . Most have firm flesh and a sweet to slightly tart taste. Their flavour is best when served at room temperature.

Storage – Store in the refrigerator , but wash them just before eating.

Classification of fruits

VINE FRUITS Examples – Grapes, passionfruit, kiwi fruit

PROPERTIES - GRAPESPhysical – small, oval shaped fruit, most containing a seed. Colour ranges from green to pale yellow and purple. Chemical - Provide fibre, Vitamin C sugar, potassium & iron.Sensory – sweet flavour. Texture is smooth, often crisp outer skin, smooth inside. Storage – need to be stored in the refrigerator

PROPERTIES – PASSIONFRUITPhysical – round or oval in shape, outer skin is leathery purple-brownish colour and wrinkles when fruit is completely ripe. Inside contains translucent orange pulp and small black seeds.Chemical - contains Vitamins A & C, also a good source of fibreSensory – fragrant aroma, sour-sweet flavourStorage – store at room temperature

Classification of fruits

STONE FRUIT - Examples - peaches, nectarines, apricots, cherries, plums

PROPERTIESPhysical – round shaped fruit, size varies depending on type. All have juicy, soft flesh surrounding a stone that contains a seed. Some (such as cherries, nectarines & plums) have smooth skin while peaches and apricots have a ‘downy’ velvety skin. Colours range from red or blue to yellow or orange depending on type.

Chemical - yellow types rich in Vitamin A and often C (eg. apricots)

Sensory – juicy flesh is generally sweet, plums are more acidic in flavour. Flavour is best when served at room temperature.

Storage – place in the refrigerator for three to five days.

Classification of fruits

MELONSExamples - cantaloupe, honeydew, watermelon

PROPERTIESPhysical - oval or ball shaped, all have a firm outer shell. Flesh comes in a range of colours, depending on the type. Watermelon has a bright pink flesh with medium black oval shaped seeds scattered throughout (unless a seedless variety) cantaloupe has many small, pale coloured contained in the centre surrounded by the orange flesh.

Chemical - cantaloupe are a good source of vitamin A, watermelon is low in kilojoules and an excellent source of Vitamin C

Sensory – Flesh of most are firm and juicy. Sweet flavour. Subtle sweet aroma.

Storage – Can store at room temperature for several days. Securely cover cantaloupe if placed in the fridge so the aroma doesn’t

contaminate other foods.

Classification of fruits

TROPICAL FRUITS Examples – bananas, pineapples, mangoes,

PROPERTIESPhysical – vary greatly in shape, size & colour.

Chemical – Bananas – high starch content before they are ripe, after ripening they are high sugar content. They are also a good source of potassium, mangoes - rich in vitamins, particularly A & C

Sensory - most are aromatic, mangoes have a soft, almost buttery texture. Sweet flavour and a distinctive perfume.

Storage- bananas best stored at room temperature. Pineapple are best eaten soon after purchase and covered if they are put in the fridge due to their strong flavour.

Selecting Fruit

Select fruit that is in season It will be likely to be fresher, cheaper, have the best flavour and

have better nutrition content.

Chose fruit that is plump and quite heavy for its size.

Avoid fruit that is damaged, bruised or wrinkled. Buy only the quantity you will use within a few

days, as overripe fruit deteriorates very quickly. If you are buying fruit in punnets, check the

condition of the ones at the bottom. Buy the best quality fruit you can afford.

Storage of Fruit

Store fruit in a cool, dry area with adequate ventilation

Refrigerator crisper is idealFruit will not continue to ripen in fridge. Therefore

make sure it is ripe when you put it in the fridge.Berries will deteriorate quickly. Purchase just

before use.Banana skins may discolour, but the flesh inside

will be consumable.

Functional properties of fruit

Colour – fruit adds contrast to dishes and when used as a garnish due to the variety of colours available.

Gelling properties - many fruits such as apples, quinces & citrus fruits have a high pectin content which forms a gel when in the presence of sugar and acid.

Texture - fruits provide a variety of textures depending on the fruits used. This adds contrast to dishes like fruit salad.

Filling- fruits add bulk to the fillings of pies such as apple, apricot or berries.

Flavour, sweetener- Apple is often combined with tart fruits to give sweetness, or to fruit juice. It can also be used to replace cane sugar in recipes like muffins.

Variety – because fruits come in a variety of flavours, textures and colours, they add variety and interest to dishes and menus.

When fruits are cooked:

During cooking, the cell walls of the fruit become tender as water passes through the cell membranes, causing the cell walls to swell and burst. As a

result, the fruit loses its shape and the pulp becomes soft

↓

If sugar is added when cooking, it strengthens the structure of the fruit and helps to retain the shape.

↓

Applying heat causes some pigment changes and some loss of colour occurs

↓

Changes in flavour occur as the naturally occurring sugars in the fruit begin to caramelise.

↓

The nutrient content is affected – for instance, vitamin C is lost due to its sensitivity to heat and exposure to oxygen.

Origin (plant or animal)Structure (images as well are really useful!)ClassificationConsideration s in food selection, including food quality and ethical issues such as fair trade and intensive farming practicesPhysical propertiesChemical propertiesSensory propertiesFunctional properties and their role in food preparation and processingChanges in the physical and sensory properties during preparation and processing