Food Biochemistry and Food Processing

22 Biochemistry of Fruit Processing 517

Advances in fruit processing technologies mostly
occur in response to consumer demands or improve-
ment in the efficiency of technology. Traditional
methods of canning, freezing, and dehydration are
progressively being replaced by fresh cut, ready-to-
eat fruit preparations. The use of modified atmos-
pheres and irradiation also helps in extending the
shelf life of produce.
Fruits are essential sources of minerals, vitamins,
and dietary fiber. In addition to these components,
they provide carbohydrates and, to a lesser extent,
proteins. Fruits play an important role in the diges-
tion of meat, cheese, and other high-energy foods by
neutralizing the acids produced by the hydrolysis of
lipids.

FRUIT CLASSIFICATION

Fruits can be broadly grouped into three categories
according to their growth latitude: temperate, sub-
tropical, or tropical regions.

TEMPERATEZONEFRUITS

Four subgroups can be distinguished among temper-
ate zone fruits. These subgroups include small fruits
and berries (e.g., grape, strawberry, blueberry, black-
berry, cranberry), stone fruits (e.g., peach, plum,
cherry, apricot, nectarine) and pome fruits, (e.g., ap-
ple, pear, Asian pear or Nashi, and European pear or
quince).

SUBTROPICALFRUITS

Two subgroups can be differentiated among sub-
tropical fruits: citrus fruits (e.g., orange, grapefruit,
lemon, tangerine, mandarin, lime, and pomelo), and
noncitrus fruits (e.g., avocado, fig, kiwifruit, olive,
pomegranate, and cherimoya).

TROPICALFRUITS

Major tropical fruits include banana, mango, papaya,
and pineapple. Minor tropical fruit include passion
fruit, cashew apple, guava, longan, lychee, mangos-
teen, carambola, rambutan, sapota, and others.

CHEMICAL COMPOSITION OF

FRUITS

CARBOHYDRATES

Fruits typically contain between 10 and 25% car-

bohydrates, less than 1% protein and less than 0.5%

fat (Somogyi et al. 1996b). Carbohydrates, sugars,

and starches are broken down into CO 2 , water, and

energy during catabolism. The major sources of car-

bohydrates are banana, plantain, date, raisin, bread-

fruit, and jackfruit. Proteins and amino acids are con-

tained in dried apricot and fig, whereas fats are the

major components of avocado and olives. Sugars are

the major carbohydrate components of fruits, and

their composition varies from fruit to fruit. In gener-

al, sucrose, glucose, and fructose are the major sug-

ar components present in fruits (Table 22.2). Several

fruits also contain sugar alcohols such as sorbitol.

VITAMINS

Fruits and vegetables are major contributors to our

daily vitamin requirements. The nutrient contribu-

tion from a specific fruit or vegetable is dependent

on the amount of vitamins present in the fruit or veg-

etable, as well as the amount consumed. The ap-

proximate percentage contribution to daily vitamin

intake from fruits and vegetables is vitamin A, 50%;

thiamine, 60%; riboflavin, 30%; niacin, 50%; and

vitamin C, 100% (Somogyi et al. 1996b). Vitamins

are sensitive to different processing conditions such

as exposure to heat, cold, reduced or high levels

of oxygen, light, free water, and mineral ions. Trim-

ming, washing, blanching, and canning can also

cause loss in the vitamin content of fruits and veg-

etables.

MINERALS

Minerals found in fruits in general may not be fully

nutritionally available (e.g. calcium, found as calci-

um oxalate in certain produce is not nutritionally

available). Major minerals in fruits are base-forming

elements (K, Ca, Mg, Na) and acid-forming ele-

ments (P, Cl, S). Minerals often present in micro-

quantities are Mn, Zn, Fe, Cu, Co, Mo, and I. Po-

tassium is the most abundant mineral in fruits,

followed by calcium and magnesium. High potassium

content is often associated with increased acidity