Food Biochemistry and Food Processing (2 edition)

(Steven Felgate) #1

BLBS102-c01 BLBS102-Simpson March 21, 2012 11:8 Trim: 276mm X 219mm Printer Name: Yet to Come

4 Part 1: Principles/Food Analysis

protein with no limiting amino acids and have 25% of the daily
fibre requirement. It would be lactose-free, nut-free, trans-fat-
free, antibiotic- and pesticide-free, artificial colour-free, no sugar
added and contain certified levels of phytosterols. The product
would contain tasteless, odourless, mercury-free, cold-pressed,
bioactive omega 3-rich fish oil harvested using animal-friendly
methods. Furthermore, it would be blood sugar-stabilising and
heart disease-preventing, boost energy levels, not interfere with
sleep, be packaged in minimal, compostable packaging and man-
ufactured using ‘green’ energy, transported by biodiesel-burning
trucks and be available to the masses at a reasonable price.
At their most fundamental levels, growing crops and raising
food animals, storing or ageing foods, processing via fermenta-
tion, developing food products, preparing and/or cooking, and
finally ingesting food are all ways of bringing about, or prevent-
ing, biochemical changes. Furthermore, methods to combat both
pathogenic and spoilage organisms are based upon biochemical
effects, including acidifying their environments, heat denatur-
ing their membrane proteins, oxygen depriving, water depriving
and/or biotin synthesis inhibiting. Only recently have the basic
mechanisms behind food losses and food poisoning begun to be
Food scientists recognised long ago the importance of a bio-
chemistry background, demonstrated by the recommendation of
a general biochemistry course requirement at the undergradu-
ate level by the Institute of Food Technologists (IFT) in the
United States more than 40 years ago. Many universities in var-
ious countries now offer a graduate course in food biochemistry
as an elective or have food biochemistry as a specialised area
of expertise in their undergraduate and graduate programs. The
complexity of this area is very challenging; a content-specific
journal, the Journal of Food Biochemistry, has been available
since 1977 for scholars to report their food biochemistry-related
research results.
Our greater understanding of food biochemistry has followed
developments in food processing technology and biotechnology,
resulting in improved nutrition and food safety. For example,
milk-intolerant consumers can ingest nutritious dairy products
that are either lactose-free or by taking pills that contain an en-
zyme to reduce or eliminate lactose. People can decrease gas
production resulting from eating healthy legumes by takingα-
galactosidase (produced byAspergillus niger) supplements with
meals. Shark meat is made more palatable by controlling the ac-
tion of urease on urea. Tomato juice production is improved
by proper control of its pectic enzymes. Better colour in potato
chips results from removal of sugars from the cut potato slices.
More tender beef results from proper aging of carcasses or at
the consumer level, the addition of instant marinades containing
protease(s). Ripening inhibition of bananas during transport is
achieved by controlling levels of the ripening hormone, ethylene,
in packaging. Proper chilling of caught tuna minimises histamine
production by inhibiting the activities of certain bacteria, thereby
avoiding scombroid or histamine poisoning. Beyond modified
atmosphere packaging, ‘intelligent’ packaging materials that re-
spond to and delay certain deteriorative biochemical reactions
are being developed and utilised. The above are just a few of the
examples that will be discussed in more detail in this chapter
and in the commodity chapters in this book.

The goal of this introductory chapter is to provide the reader
with an overview of both basic and applied biochemistry as they
relate to food science and technology, and to act as a segue
into the following chapters. Readers are strongly encouraged to
consult the references provided for further detailed information.


‘Carbohydrate’ literally means ‘carbon hydrate,’ which is re-
flected in the basic building block unit of simple carbohydrates,
i.e. (CH 2 O)n. Carbohydrates make up the majority of organic
mass on earth having the biologically important roles of energy
storage (e.g. plant starch, animal glycogen), energy transmission
(e.g. ATP, many metabolic intermediates), structuralcomponents
(e.g. plant cellulose, arthropod chitin), and intra- and extracel-
lular communication (e.g. egg-sperm binding, immune system
recognition). Critical for the food industry, carbohydrates serve
as the primary nutritive energy sources from foods like grains,
fruits and vegetables, as well as being important ingredients for
many formulated or processed foods. Carbohydrates are used
to sweeten, gel, emulsify, encapsulate or bind flavours, can be
altered to produce colour and flavour via various browning re-
actions, and are used to control humidity and water activity.


The basic unit of a carbohydrate is a monosaccharide;
2 monosaccharides bound together are called a disaccharide;
3 are called a trisaccharide, 2–10 monosaccharides in a chain are
termed an oligosaccharide, and 10 or more are termed a polysac-
charide. The simplest food-related carbohydrates, monosaccha-
rides, are glucose, mannose, galactose and fructose.
Carbohydrate structures contain several hydroxyl groups
(–OH) per molecule, a structural feature that imparts a high
capacity for hydrogen bonding, making them very hydrophilic.
This property allows them to serve as a means of moisture con-
trol in foods. The ability of a substance to bind water is termed
humectancy, one of the most important properties of carbo-
hydrates in foods. Maltose and lactose (discussed later) have
relatively low humectancies; therefore, they allow for sweet-
ness while resisting adsorption of environmental moisture. Hy-
groscopic (water absorbing) sugars like corn syrup and invert
sugar (hydrolysed table sugar) help prevent water loss, e.g. in
baked goods. In addition to the presence of hydroxyl groups,
humectancy is also dependent on the overall structures of car-
bohydrates, e.g. fructose binds more water than glucose.

Sugar Derivatives – Glycosides

Most chemical reactions of carbohydrates occur via their hy-
droxyl and carbonyl groups. Under acidic conditions, the car-
bonyl carbon of a sugar can react with the hydroxyl of an alcohol,
e.g. methanol (wood alcohol) to formO-glycosidic bonds. Other
examples of glycosidic bonds are those between sugar carbonyl
groups and amines (e.g. some amino acids as well as molecules
such as DNA and RNA building blocks), as well as sugar
carbonyl bonding with phosphate (e.g. phosphorylated
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