BLBS102-c09 BLBS102-Simpson March 21, 2012 11:15 Trim: 276mm X 219mm Printer Name: Yet to Come
9 Enzymes in Food Processing 195pancreatic lipases. In this regard, an understanding of lipase
structure and function relationship as well as lipase catalytic
mechanism is crucial for the development of inhibitors for
pharmacological and medical use. The well-known drug
Orlistat (also known as xenical or tetrahydrolipstatin) used to
treat obesity acts by blocking digestive lipase action, leaving
consumed fat undigested (Halford 2006). The basic polypeptide,
protamine, is a natural lipase inhibitor and acts to hinder fat
absorption (Tsujita et al. 1996). Several soy proteins including
lipoxygenase-1 are able to inhibit pancreatic and microbial
lipases (Satouchi et al. 2002). The inhibitory capacity of
soybean proteins has been attributed to interactions with lipids
and the ability to transform the substrate emulsion. There are
also reports of other promising natural inhibitors of lipases, e.g.,
medicinal plant extracts (Sharma et al. 2005), polyphenolics,
e.g., resveratrol, catechins, and 3-O-trans-p-coumaroyl actinidic
acid from red wine, green tea, and kiwi fruit (Armand 2007,
Koo and Noh 2007, Jang et al. 2008).
While high dietary fat can cause severe adverse health effects
(including cardiovascular diseases and cancer), some amount of
fat is absolutely required to serve as components of biological
membranes, hormones, vitamins, etc. Thus, an adequate supply
of essential fats in the diet is important to sustain human health.IsomerasesThis group of enzymes catalyzes structural rearrangement of
molecules into their corresponding isomers. Thus, for the gen-
eral reaction A→B, catalyzed by an isomerase, A and B are
isomers. While several isomerases have been characterized in
the literature, the one with food use is glucose isomerase, or
more specifically, xylose isomerase (Chaplin and Burke 1990).
The enzyme is produced from several microorganisms, such as
Actinoplanes missouriensis,B. coagulans, Streptomyces albus,
S. olivaceus, andS. olivochromogenes, and it normally isomer-
izesd-xylose tod-xylulose, that is,D-Xylose⇔D-XyluloseHowever, this same enzyme can act ond-glucose and isomer-
ize it tod-fructose, that is,D-Glucose⇔D-Fructosed-fructose is about 30% sweeter than bothd-glucose andd-
xylose, and plays an important role in the food industry as a
sweetener or component of sweeteners; hence, the enzyme is
commonly referred to as glucose isomerase instead of its more
apt name xylose isomerase.
The free form of the enzyme is quite expensive; thus, it is
produced in the immobilized form to permit reuse and reduce
cost for the commercial production of fructose fromd-glucose.
Thus, high-fructose corn syrup (HFCS) is produced through iso-
merization by glucose isomerase fromd-glucose derived from
the hydrolysis of corn starch. To make HFCS, corn starch is first
converted to liquefied starch byα-amylase and subsequently
to glucose by glucoamylase before the isomerization step. The
fructose yield in HFCS is temperature dependent, with much
higher yields (about 55%) recovered at 95◦C versus 42% at theconventional 60–70◦C production temperature. The high ther-
mal stability of glucose isomerase permits its use at high tem-
peratures.ENZYMES IN FOOD AND FEED
MANUFACTUREEnzymes from plants, animals, and microorganisms have been
used since time immemorial to modify foodstuffs. Examples of
the food enzymes of plant origin include papain, bromelain, and
ficin; examples of animal enzymes include rennets, pepsins,
trypsins, chymotrypsins, pancreatic lipases, lysozyme, and
cathepsins; and examples of microbial enzymes are various amy-
lases, cellulases, proteases, lipases, TGases, glucose isomerase,
and GOX derived from selected bacteria, yeasts, and fungi. The
uses of these enzymes in foods result in desirable changes with
respect to improvements in appearance, consistency, flavor, sol-
ubility, texture, and yield, among others. In this regard, enzymes
have been used as processing aids in the manufacture of various
baked goods, dairy products, meats and fish products, beverages
(alcoholic and nonalcoholic), etc. (Table 9.2).Baked GoodsBaked goods are prepared from flours such as wheat flour, which
has starch as its main constituent. Amylolytic enzymes break
down flour starch into small dextrins that become better sub-
strates for yeast to act upon in the bread-making process. The
use of enzymes in the baking industry is expanding to replace
the use of chemicals in making high-quality products, in terms
of better dough handling, anti-staling properties, as well as tex-
ture, color, taste, and volume. For example, enzymes like GOX
and lipase are used in baked goods to strengthen dough texture
and enhance elasticity in place of chemicals such as potassium
bromate and ascorbate. Other enzymes used in the baking indus-
try include LOX for bleaching flour and strengthening doughs;
proteases for degrading and weakening gluten to impart “plas-
tic” properties to doughs and make them more suitable for the
making of biscuits; pentosanases (also known as xylanases) for
enhancing dough machinability to result in more flexible, easier-
to-handle stable doughs that provide better crumb texture and
increased loaf volume; and asparaginases employed to curtail the
formation of acrylamide in baked goods derived from cereal- and
potato-based flours. The enzyme asparaginase breaks down as-
paragine in the flours to reduce its availability for reaction with
reducing sugars to form acrylamide at high temperature.Dairy ProductsThe formulation of dairy products entails the use of several
enzymes, such as proteases (e.g., microbial rennets or their ho-
mologs from calf and other ruminants), lipases, and lactases.
The proteases are used to precipitate milk caseins as “clots” or
“curds” during cheese-making; the proteases and lipases also
promote flavor development during ripening of cheese and in
products like coffee whiteners, snack foods, soups, and spreads
(margarines); while lactases are used to produce lactose-free