Food Biochemistry and Food Processing (2 edition)

BLBS102-c28 BLBS102-Simpson March 21, 2012 13:54 Trim: 276mm X 219mm Printer Name: Yet to Come

566 Part 5: Fruits, Vegetables, and Cereals

Sliced Apples

Sliced apples have multiple uses and are preserved by many

different methods such as canned, refrigerated, frozen, or dehy-

drated states. About 85% of sliced apples are processed, whereas

only 15% are refrigerated, frozen or dehydrated and frozen. Ap-

ple slice texture is very important, as well as the consistency of

the slice size, therefore, apples with firm flesh and high-quality,

falling within a specified size range are desirable. Apples are

sliced into 12–16 slices and blanched after inspection for even-

tual defects. The blanched apple slices are hot filled into cans and

closed under steam vacuum after addition of hot water or sugar

syrup. The canned apples are heated at 82.2◦C and immediately

cooled to 37–40◦C.

When bulk frozen, apple slices are vacuum treated and

blanched and filled into 13–15 kg tins or poly-lined boxes. The

tins or boxes are then sealed, frozen, and stored at− 17 ◦C.

Individual quick frozen apple slices (IQF) are usually treated

with sodium bisulfite after inspection. Nitrogen (N 2 ) and carbon

dioxide (CO 2 ) are the most popular freezing media. From the

vacuum tank, the apple slices pass through an IQF unit where

the slices are individually frozen. From the freezing unit, the

slices are filled into tins or poly-lined boxes and stored frozen at

− 17 ◦Corbelow.

Dehydrofrozen apple slices are dehydrated to less than 50% of

their original weight and then frozen. The dehydrofrozen slices

are packed in cardboard containers or large metal cans with

polyethylene liners and rapidly frozen before storing. Frozen

slices are thawed and then soaked in a combined solution of

sugar, CaCl 2 , and ascorbic acid, or bisulfite. For fresh and re-

frigerated apple slices, the use of 0.1–0.2% calcium chloride,

and ascorbate protects apple slices from browning and micro-

bial spoilage. Blanched slices resist browning for approximately

2 days, but lose flavor, sugar, and acid. This type of product has a

very short shelf life. Recently, the use of natural protein polymer

coatings (NatureSeal) has shown promise in enhancing the shelf

life and quality of fresh-cut apple products.

Dried Apple Products

Most processing cultivars are used for drying, but the best qual-

ity dried apple slices are obtained from “Red Delicious” and

“Golden Delicious” apples. A desirable quality attribute of ap-

ples used for drying is a high sugar/water ratio. Color preserva-

tion and reduction in undesirable enzyme activities are achieved

by the use of bisulfite.There are two types of dried apple prod-

ucts including evaporated and dehydrated apples. Evaporated

apples are cut into rings, pie pieces, or dices and then dried to

less than 24% moisture by weight. The dehydrated apples, on

the other hand, are cut into dices, pie pieces, granules, and flakes

prior to drying to 3–0.5% moisture content. Up to 300 ppm of

bisulfite is used to prevent color deterioration. The maximum

allowed SO 2 in dried apples in Europe is 500 ppm, whereas in

United States, the limit is 1000 ppm.

Quality Control

Apples contain several organic acids and as such, only a limited

number of microorganisms can grow in them. The most com-

mon microbes are molds, yeasts, aciduric bacteria, and certain

pathogens such asE. coliO157:H7, capable of growing at low

pH (Swanson 1989). Several approaches to quality management

are available today including total quality management (TQM),

statistical quality control (SQC), and hazard analysis critical

control points (HACCP).

Biochemical Composition and Nutritional

Value of Processed Apples

The nutritive value of most processed apple products is similar to

the fresh raw product. Apple products are sources of potassium,

phosphorus, calcium, vitamin A, and ascorbic acid. Glucose,

sucrose, and fructose are the most abundant sugars. Dried or

dehydrated apples have a higher energy value per gram tissue

due to the concentration of sugars (Tables 28.4 and 28.5).

The nutritional value of apples, and fruits in general, is en-

hanced by the presence of flavonoids. More than 4000 flavonoids

have been identified to date. There are many classes of flavonoids

of which flavanones, flavones, flavonols, isoflavonoids, antho-

cyanins, and flavans are of interest. Flavanones occur predom-

inantly in citrus fruits, anthocyanins, catechins, and flavonols

are widely distributed in fruits, and isoflavonoids are present in

Table 28.5.Nutrients in Fruits and Processed Products (454 g)

Apples Food Energy (kcal) Protein (g) Fat (g) Carbohydrate (g) Calcium (mg) Phosphorus (mg) Iron (mg)

Raw fresh 242 0.8 2.5 60.5 29 42 1.3

Applesaucea 413 0.9 0.5 108.0 18 23 2.3

Unsweetened Juice 186 0.9 0.9 49.0 18 23 2.3

Apple juice 213 0.5 0.1 54.0 27 41 2.7

Frozen sliceda 422 0.9 0.5 110.2 23 27 2.3

Apple buttera 844 1.8 3.6 212.3 64 163 3.2

Dried, 24% 1247 4.5 7.3 325.7 141 236 7.3

Dehydrated, 2% 1601 6.4 9.1 417.8 181 299 9.1

Source: Composition of foods. Agriculture Handbook No 8.

aWith sugar.