Food Biochemistry and Food Processing

22 Biochemistry of Fruit Processing 531

slices from browning and microbial 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 quali-
ty of fresh cut apple products.

Dried Apple Products

Most processing cultivars are used for drying, but
the best quality dried apple slices are obtained from
“Red Delicious” and “Golden Delicious” apples. A
desirable quality attribute of apples used for dry-
ing is a high sugar/water ratio. Color preservation
and reduction in undesirable enzyme activities are
achieved by the use of bisulphite. There are two
types of dried apple products 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 ap-
ples on the other hand, are cut into dices, pie pieces,
granules and flakes prior to drying to 3–0.5% mois-
ture content. Up to 300 ppm of bisulphite is used to
prevent color deterioration. The maximum allowed
SO 2 in dried apples in Europe is 500 ppm, whereas
in the United States, the limit is 1000 ppm.

QUALITYCONTROL

Apples contain several organic acids, and therefore
only a limited number of microorganisms can grow
in them. The most common microbes are molds,
yeasts, aciduric bacteria, and certain pathogens such
as E. coliO157:H7 that are 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).

BIOCHEMICALCOMPOSITION AND

NUTRITIONALVALUE OFPROCESSEDAPPLES

The nutritive value of most processed apple prod-

ucts is similar to that of the fresh raw product. Apple

products are sources of potassium, phosphorus, cal-

cium, vitamin A, and ascorbic acid. Glucose, su-

crose, 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 22.4 and 22.5).

The nutritional value of apples, and fruit in gener-

al, is enhanced by the presence of flavonoids. More

than 4000 flavonoids have been identified to date.

There are many classes of flavonoids, of which fla-

vanones, flavones, flavonols, isoflavonoids, anthocy-

anins, and flavans are of interest. Flavanones occur

predominantly in citrus fruits; anthocyanins, cate-

chins, and flavonols are widely distributed in fruits;

and isoflavonoids are present in legumes. Structur-

ally, flavonoids are characterized by a C 6 —C 3 —C 6

carbon skeleton (Fig. 22.7). They occur as aglycones

(without sugar moieties) and glycosides (with sugar

moieties). Processing may decrease the content of

flavonoids by up to 50%, due to leaching into water or

removal of portions of the fruit, such as the skin, that

are rich in flavonoids and anthocyanins. It is estimat-

ed that the dietary intake of flavonoids may vary from

23 to 1000 mg/day in various populations (Peterson

Table 22.4.Protein, Fat, and Carbohydrate Nutrients in Fruits and Processed Products (454 g)

Food Energy Protein Fat Carbohydrate
Apples (kcal) (g) (g) (g)
Raw fresh 242 0.8 2.5 60.5
Applesaucea 413 0.9 0.5 108.0
Unsweetened Juice 186 0.9 0.9 49.0
Apple juice 213 0.5 0.1 54.0
Froz. Sliceda 422 0.9 0.5 110.2
Apple buttera 844 1.8 3.6 212.3
Dried, 24% 1247 4.5 7.3 325.7
Dehyd. 2% 1601 6.4 9.1 417.8
Source:www.nal.usda.gov/fnic.
aWith sugar.