Food Biochemistry and Food Processing

22 Biochemistry of Fruit Processing 529

evaporator is to heat the juice to about 90°C and
capture the volatile (aroma) components by cooling
and condensation. This is followed by reheating the
20–25° Brix juice concentrate from the first stage to
about 100°C and concentrating it to about 40–45°
Brix. Another stage of heating and evaporation at
about 50°C to 60° Brix, and final heating and con-
centration in the fourth stage to 71° Brix, provides
fully concentrated juice. The warm concentrate is
then chilled to 4–5°C prior to adjusting the Brix to
70° before barreling or bulk storage.
Chemicals such as benzoic acid, sorbic acid, and
sulphite are sometimes used to reduce spoilage of
unpasteurized apple juice, either in bulk or as an aid
in helping to preserve refrigerated products. Irrad-
iation and ultrasonication are new, emerging meth-
ods of preservation with high potential, even though
they are not fully accepted by consumers at this
time.
Apple essence is recovered during the concentra-
tion of apple juice. The identification of volatile
apple constituents, commonly known as essence or
aroma, has been the subject of considerable re-
search. In 1967, researchers at the U.S. Department
of Agriculture (USDA) identified 56 separate com-
pounds from apple essence. These compounds were
further refined by organoleptic identification using a
trained panel of sensory specialists. These laborato-
ry evaluations revealed 18 threshold compounds
identified as “Delicious” apple compounds consist-
ing of alcohols, aldehydes, and esters. Three of the
18 compounds had “apple-like aromas” according
to the taste panel. These were 1-hexanal, trans-2-
hexenal, and ethyl-2-methyl butyrate (Flath et al.
1967, Somogyi et al. 1996b).

PROCESSEDAPPLEPRODUCTS

The popularity of blended traditional and tropical
juice products has pushed the consumption of tradi-
tional fruit juices such as apple, orange, and grape
juices to 25 L in 2002, an increase of more than 24%
from 1992 (Statistics Canada 2003). Apples are nor-
mally processed into a variety of products, although
apple juice is the most popular processed apple prod-
uct. With a production of 465,418 metric tons (mt) of
apple in 2001, Canada exported 18,538 mt of con-
centrated apple juice. For the same year, the United
States exported 25,170 mt of concentrated apple
juice (FAO 2003). Apples for processing should be

of high quality, proper maturity, of medium size, and

uniform in shape. Apples are processed into, frozen,

canned, dehydrated apple slices and dices, and dif-

ferent kinds of applesauce. Apples that are unsuit-

able for peeling are diverted to juice processing.

Applesauce

Diced or chopped apples with added sugar, prefer-

ably a sugar concentrate, are cooked at 93–98°C for

4–5 minutes in order to soften the fruit and inacti-

vate polyphenol oxidase. Sauce with a good texture,

color, and consistency is produced with high quality

raw apples and a good combination of time and

temperature treatment. Cooked applesauce is passed

through a pulper with a 1.65–3.2 mm finishing

screen to remove unwanted debris and improve the

texture. Applesauce is then heated to 90°C and im-

mediately filled in glass jars or metal cans. The filled

containers are seamed or capped at 88°C and cooled

to 35–40°C after 1–2 minutes (Fig. 22.6). There are

various types of applesauce; these include natural,

no sugar added, “chunky,” and cinnamon apple-

sauces, and mixtures of applesauce and other fruits

such as apricot, peach, or cherry.

Sliced Apples

Sliced apples have multiple uses and are preserved

by many different states including canned, refriger-

ated, frozen, or dehydrated states. About 85% of

sliced apples are processed, whereas only 15% are

refrigerated, frozen, or dehydrated and frozen (de-

hydrofrozen). Apple slice texture and the consisten-

cy of the slice size are very important; therefore,

apples with firm flesh and high quality, falling with-

in a specified size range, are desirable. Apples are

sliced into 12 to 16 slices and blanched after inspec-

tion for eventual defects. The blanched apple slices

are hot-filled into cans and closed under steam vacu-

um after the addition of hot water or sugar syrup.

The canned apples are heated at 82.2°C and immedi-

ately cooled to 37–40°C.

When bulk frozen, apple slices are vacuum treated,

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 bisulphite after inspec-

tion. Nitrogen (N 2 ) and carbon dioxide (CO 2 ) are the