Food Biochemistry and Food Processing (2 edition)

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22 Part 1: Principles/Food Analysis

Table 1.20.Selected Commercial
Biotechnology-derived Food Enzymes

Enzyme Application

Acetolactate decarboxylase (EC
4.1.1.5)

Beer aging and diacetyl
reduction
α-Amylase (EC 3.2.1.1) High-fructose corn syrup
production
Amylo-1,6-glucosidase (EC
3.2.1.33)

High-fructose corn syrup
production
Chymosin (EC 3.4.23.4) Milk clotting in cheese
manufacturing
Lactase (EC 3.2.1.108) Lactose hydrolysis
Glucan-1,4-α-maltogenic
α-amylase (EC 3.2.1.133)

Anti-stalling in bread

Source: Roller and Goodenough 1999, Anonymous 2004, IUBMB-NC
website (www.iubmb.org).

very complex due to degradation of genetic material as the re-
sult of processing conditions. Detecting misrepresentation of
food components is a task well-suited for DNA-based detec-
tion in the case of meat species of origin, especially when the
meat product is processed such that appearance and physical
traits cannot easily cue experts as to product identity. Gene se-
quences within mitochondrial DNA are usually used as the PCR
targets for such purposes (Wiseman 2009). For example, differ-
ent tuna species can be differentiated (Michelini et al. 2007).
Likewise, the presence of meat in cattle feed can be assayed
(Rensen 2005). Such tests can be done for high-heat-processed
samples at a low cost, and such tests can be highly automated
for steps post sample collection. Lastly, another example of a
food authentication application for PCR is the case of detecting
the presence and/or the quantity of genetically modified ingredi-
ents in a food. For the purposes of quantification, real-time PCR
must be used (Wiseman 2009), the most modern type of PCR
technology, because it is capable of highly precise, quantitative
determinations. This capability is due to real-time PCR’s ability
to very quickly and accurately modulate PCR reaction tempera-
ture via the use of low-volume reactions. Jurisdictions that have

Table 1.21.Selected Genetically Modified
Microorganisms Useful in Food Processing

Microorganism Application

Lactobacillus lactis Phage resistance, lactose
metabolism, proteolytic activity,
bacteriocin production
Saccharomyces
cerevisiae(Baker’s
yeast, Brewer’s yeast)

Gas (carbon dioxide) production
in sweet, high-sugar dough
Manufacture of low-calorie beer
(starch degradation)

Source: Hill and Ross 1999, Roller and Goodenough 1999,
Anonymous 2004.

GM labelling laws (e.g. the European Union) can thus verify the
correct labelling of incoming ingredients.
In the authentication process, DNA within foods can also be
characterised and differentiated by use ofDNA probes, an earlier
food authentication technology that dates back to at least 1990,
where it was used to distinguish between heat-processed rumi-
nant (goat, sheep and beef), chicken and pig meat (Chicuni et al.
1990). DNA probes are short pieces of DNA (Rensen et al. 2005)
that contain a detectable feature (usually fluorescence) and that
are complementary to a DNA sequence of interest. Thus, a signal
is produced only if the probed sequence is present in the food,
since the probe will bind only to its complement in a manner
that yields a signal. In order to probe a food product, genetic
material is isolated and immobilised on a piece of nitrocellulose
(blotting), which is then ‘probed’ with a DNA complementary
probe. The information from the above types of DNA-based au-
thentication tests can aid in processing quality control to ensure
both authenticity and safety at relatively cheap cost.

NATURAL TOXICANTS


The contamination of various foods by toxicants may occur
as a result of microbial production, crop plant production or
ingestion by animals for human consumption. Microbial sources
of toxins are mycotoxin-producing fungi and toxin-producing
bacteria. Notable examples of microbially derived toxins are
botulinum toxin produced byClostridium botulinumand the
Staphylococcus aureustoxin. These toxins are produced in the
food itself and result in food poisoning. Both toxins are heat-
labile; however, the extreme toxicity of the botulinum toxin,
potent at 10−^9 g per kg body weight, makes it of particular
concern for food processing of anaerobically stored foods.
Mycotoxins are extremely toxic compounds produced by cer-
tain filamentous fungi in many crop plants (Richard 2007). In-
gestion of mycotoxins can be harmful to humans via contami-
nated foods or feed animals via their feed, particularly in maize,
wheat, barley, rye and most oilseeds. Mycotoxins produce symp-
toms that include nervous system disorders, limb loss and death.
Aflatoxins are a well-studied type of mycotoxin that are known
carcinogens. An example of a mycotoxin structure, aflatoxin
B1, is shown in Figure 1.6. Mycotoxin poisoning can take place
either directly or indirectly, through consumption of a contam-
inated food or by a food ingredient that may be contaminated
and subsequently eaten as part of a final product.

O

O

O

O O

O

Figure 1.6.The structure of aflatoxin B1, produced byAspergillus
flavusandA. parasiticus.
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