Food Biochemistry and Food Processing

1 Food Biochemistry—An Introduction 19

acid, phosphoric acid), enzyme inhibitors, enzyme

treatment, and complexing agents. Application of

these inhibitors of enzymatic browning is strictly

regulated in different countries (Eskin 1990, Gopa-

kumar 2000, Kim et al. 2000).

ETHYLENEPRODUCTION INFRUITRIPENING

Ethylene acts as one of the initiators in fruit ripen-

ing. Its concentration is very low in green fruits but

can accumulate inside the fruit and subsequently

activates its own production. Table 1.16 lists the

enzymes in the production of ethylene starting from

methionine. The effect of ethylene is commonly

observed in the shipping of bananas. The banana is a

climacteric fruit with a fast ripening process. During

shipping of green bananas, ethylene is removed

through absorption by potassium permanganate to

render a longer shelf life.

REDUCTION OFPHYTATE INCEREALS

Phytic acid (myo-inositol hexaphosphate) is the

major phosphate reserve in many seeds. Since it

exists as a mixed salt with elements such as potassi-

um, magnesium, and calcium (and as such is called

phytin or phytate), it is also a major source of these

macronutrient elements in the seed. However, this

salt form of macronutrients renders them unusable

by the human body. During seed germination, phy-

tase (4-phytase, phytate-6-phosphatase, EC 3.1.3.26)

hydrolyzes the phytic acid to release phosphate, its

associated phosphate cation, and 1-D-myo-inositol

1,2,3,4,5-pentakisphosphate. Breakdown of phytate

is rapid and complete (Stauffer 1987a,b; Berger

1994; Bewley 1997). This enzymatic reaction re-

leases the macronutrients from their bound forms so

they are more easily utilized by the human body.

This explains why breads utilizing flour from germi-

nated wheat are more nutritious than those made

from regular wheat flour.

BIOTECHNOLOGY IN FOOD

PRODUCTION, HANDLING, AND

PROCESSING

BIOTECHNOLOGY-DERIVEDFOODENZYMES

With the advancement of biotechnology, the food

industry was not slow in jumping on the wagon for

Figure 1.3.Degradation of adenosine triphosphate
(ATP) in seafoods. ATP phosphohydrolase (EC
3.6.3.15), ADPase (EC 3.6.1.6), AMP deaminase (EC
3.5.4.6), 5’-nucleotidase (EC 3.1.3.5), Inosine nucleoti-
dase (EC 3.1.3.5), Xanthine oxidase (EC 1.1.3.22). [Gill
2000, Gopakumar 2000, IUBMB-NC website
(www.iubmb.org)]