FLEISCHWIRTSCHAFT international 6/2017

............................................
28
Fleischwirtschaft international 6_2017
Coatings
Apromising way to extend shelf life
Source: KUMAR et al. FLEISCHWIRTSCHAFT international 6_2017
Fig. 2: Collagen forms athermal-sensitive triple-helix.
paramountly important for any processor (KUMAR andTANWAR,2011).
Consumers’ present slogan is “safe food”which has become great concern
for meat processor and marketing channels to provide foods of consumer’s
choice. Consumers demand foods with high nutritional value that are free
from chemical preservatives and are microbiologically safe. On the other
side, meat is an ideal medium for many microbes to grow because it is
high in moisture, rich in nitrogenous compounds (essential amino acids,
proteins), and agood source of minerals, vitamins and other growth factors.
Furthermore, its pH is favorable for growth of most micro-organisms.
In general for controlling the microbial growth in food, it is needed to
consider the hydrogen ion concentration, water activity (aw), oxidationreduction
potential (Eh) and effif cacy of anti-microbial agents.
Lipid oxidation is one of the major causes of deterioration in the quality
of meat and meat products. It may also decrease the nutritional value by
forming potential toxic products during cooking and processing (SHAHIDI
et al., 1992; MAILLARD et al., 1996). Oxidation of unsaturated fatty acids in
cooked meats during storage and reheating results in stale or rancid fl
avors
known as Warmed-Over Flavor (WOF) (SATO and HEGARTY,1971).Unsaturated
lipids, especially those of the membrane phospholipids fraction, are
the compounds undergoing auto-oxidation (IGENE and PEARSON,1979;
YOUNATHAN and WATTS,1960).
The modus-operandi of any food preservative is either to restrict microbial
activity or check enzymatic, chemical and physical reactions that cause
deterioration and spoilage of food. To check microbial spoilage, the food
preservatives act by either restricting the amount or making those substrates
inaccessible to microbes, which are required by microbes for their
growth. The best way to preserve food is to either lower the water content
by thermal treatment or lower the pH of food or both. In addition, other
methods of food preservation include storage of food at lower temperature
(refrigeration or freezing), irradiation or use of chemical preservatives
including organic acids and humectants to lower the aw.Chemical preservatives,
however,are not preferred now-a-days due to their residual effects
and declining consumer preference. Therefore more and more emphasis is
being laid on bio- and phyto-preservatives i.e., use of natural preservatives
either alone or in combination with other methods.
Natural preservatives can be categorized into:
r desirable microbes and/ or their metabolites (Nisin, Natamysin and
Fermentate: afungal product)
r certain naturally occurring antimicrobial constituents of other foods
(Lysozymes, Phosvitin, Cystatin and Lactoferrin)
r protein hydrolysates/ bioactive peptides derived from food proteins and
r plant derived products (herbs and spices).
The use of different types of proteins from
various sources as functional food ingredients
in processed meat is being practiced for
centuries but it is only in recent years that
modern science has started paying much
attention to the exploitation of desirable
properties of protein and application of
protein coatings on processed food products
for enhancing its shelf life.
Extending meat shelf-life
with edible coatings
Extending the shelf-life of meat provides
many benefi
ts to the industry and the consumer.Itisimportant
to extend the shelf-life
of meat so the amount of deliveries can be
reduced (MEAD,2004). Additionally,retailers
would have more options for displaying the
product. Most importantly,ifthe shelf-life of
meat could be extended, the large amount of
meat that is annually disposed would be
drastically reduced. Specifi
cally,over one
billion dollars is wasted annually due to the
unattractive discoloration of meat products
that occurs prior to unacceptable microbial
counts (HERMEL,1993). The development of edible fi
lms from animal
proteins can be an innovative approach to enhance the nutritive value of
food products. These edible films have avariety of advantages such as
biodegradability,edibility,biocompatibility,aesthetic appearance, barrier
properties against oxygen and physical stress.
Milk proteins based fi
lms have better mechanical and barrier properties
than polysaccharide based materials and other plant protein based films.
The mechanical and barrier properties of fi
lms is directed by the quality of
milk proteins and additives, as the presence of triglycerides in milk proteins
network signifi
cantly improve water vapor properties, due to low
polarity.Inaddition, the incorporation of natural antimicrobial and antioxidant
substances in the milk based fi
lms may help in the extension of storage
life of meat products.
Collagen (Fig. 2) and gelatin are also very important components of
animal proteins used for edible fi
lm manufacture. Collagen, amajor fraction
of connective tissue in animals, has been used commercially as a
protein coating because it has great oxygen barrier properties, however,the
moisture barrier is low (KROCHTA and DE MULDER-JOHNSON,1997). Collagen
also has the tendency to melt when meat is cooked (Fig. 3). Gelatin, the
Fig. 3: Collagen melts when cooked.