FLEISCHWIRTSCHAFT international 6/2017

Fleischwirtschaft international 6_2017
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Apromising way to extend shelf life
Coatings
partially denatured product of collagen, can also be used to both reduce
oxygen and moisture migration, and as acarrier for antimicrobial and
antioxidant compounds. Gelatin has better moisture barrier properties
than collagen (GENNADIOS et al., 1997). Generally gelatin is amixture of
proteins derived from collagen, and most commonly used as afood ingredient
to improve the texture and increase the water-holding capacity of
foods (MENDIS et al., 2005).
Extending meat shelf-life with collagen/ gelatin coatings
Gelatins with larger molecules give atougher coating when applied on the
meat surface. The coating of gelatin on the meat surface requires heat
which allows the gelatin to go into solution. Temperature range between
32–52 °C has been recommended for gelling and application. The optimum
gelatin concentration of 15–55% (w/w) has been reported for good
coating; however,best results were obtained when the gelatin ranged
between 20–30%. These ranges were especially favored in terms of adherence
to the meat surface (OLSEN andZOSS,1985). Various methods such as
dipping, spraying, cascading, or painting it onto afood’s surface could be
done for coating purpose (KEIL et al., 1960). WHITMAN et al. (1971) reported
that spray application was preferred because it allowed uniform film thickness.
KEIL et al. (1960) observed that when the food product was removed
from the application of the solution, it gelled in acool environment in
0.5 min, but took 1–2 hto completely dry.Inpreparing the solution, additionally,KEIL
et al. (1960) reported that agelatin with ahigher bloom rating
gelatinized faster than gelatin with alow bloom rating. However,ina
process used by OLSEN and ZOSS (1985) where fried food products were
spray-coated with asolution containing 25–35% gelatin, low strength
gelatins, those with aBloom value of 150orless, were favored because they
formed agel at lower temperatures.
Saving sensory characteristics
The application of collagen or gelatin coatings has no negative effect on the
sensory characteristics of the meat products, and in some cases, improves
the sensory qualities of meat. PRABHU et al. (2004) reported that sensory
panelists could not tell the difference between frankfurters and restructured
ham, with incorporated pork collagen at 1and 2%, and control frankfurters
and restructured ham. RICE (1994) also observed that beef cubes
wrapped in acollagen film and stored for 20 weeks at 0°C, showed little
difference in sensory attributes from the plastic-wrapped controls.
MARGGRANDER and HOFMANN (1997) observed that a10% solution of
gelatin that was sprayed onto pork bellies and stored frozen for 12 months
produced an acceptable product, while the controls in the experiment had
an off-flavor,scent, and aroma. In the same study,after 18 months, the
sensory analysis showed that the coated samples were acceptable while the
untreated samples were inedible.
Avoiding flavor deterioration
Processed meat flavor can be maintained by applying low oxygen permeable
films as coating material. Reports show that the application of edible
collagen coatings reduce the onset of lipid oxidation, which correlates to
flavor deterioration, in meat products during storage. RICE (1994) stated
that beef cubes wrapped in acollagen film and stored for 20 weeks at 0°C,
showed little difference in oxidation from the plastic-wrapped controls.
Gelatin coatings are also effective in reducing the onset of lipid oxidation of
frozen meat products. MARGGRANDER and HOFMANN (1997) reported that
pork bellies that were spray-coated with a10% solution of gelatin and
stored frozen up to 18 months had lower TBARS values than controls.
VILLEGAS et al. (1999) reported that ham and bacon pieces that were dipped
into a2,4,or6%solution of gelatin and packaged either aerobically or
under vacuum, and stored frozen for seven months, showed significantly
lower lipid oxidation in comparison to controls, in both packaging techniques.
FAROUK et al. (1990) reported that beef round steaks with acollagen
coat that were either vacuum-packaged or tray-packaged with PVC, and
either stored frozen or refrigerated for one week, did not show asignificant
difference in TBA values from controls, even though TBA values remained
low for all of the samples. ANTONIEWSKI et al. (2007) reported no significant
difference between TBARS numbers of fresh beef and pork loins, salmon
fillets, and chicken breasts coated with a20% bovine gelatin solution and
respective controls after all samples were stored for 14 days, under 1050 lux
fluorescent light, in 80% O2 and 20% CO2 MAP, at 4°C.
Reducing purge
Water is the main component of meat (75%), followed by protein (15–24%),
and fat (1–10%). Packaged meat becomes unattractive when there is water
loss during storage (GENNADIOS et al., 1997). The moisture content of meat
depends on the structural orientation of protein, as the amount of free water
in the meat depends upon the space between the myofilaments. More water
is expelled as the space between thick and thin filaments is reduced. Capillary
forces within the myofilaments hold about 60–70% of the water in meat
(BERG,2001).INSAUSTI et al. (2000) stated that the initial pH of meat is an
important variable in determining the shelf-life of meat because it influences
the water-holding capacity,thereby influencing the meat texture and
tenderness. Many studies show that the use of collagen and gelatin coatings
on fresh meat products reduces the amount of purge that collects in the
bottom of meat trays over the time. If an edible coating reduced water loss
in meat products, absorbent pads at the bottom of the package could be
eliminated. Areduction of purge would also help to maintain the flavor,
texture, color,and weight. Even though collagen does not have good moisture
barrier property,collagen coatings have been shown to reduce the
amount of purge lost in meat products. Agelatin coating reduces purge in
meat products because it acts as awater barrier.Gelatin is able to act as a
barrier to water because it has moderate surface activity (FINCH and
JOBLING,1977). Substances that have high surface tension repel water;
hence, the gelatin coat inhibits purge from accumulating in the bottom of
meat trays. FAROUK et al. (1990) reported that beef round steaks with a
collagen coat, vacuum-packaged or tray-packaged with PVC, and either
stored-frozen or refrigerated, for one week, had less purge than controls.
RICE (1994) reported that beef cubes wrapped in acollagen film and stored
for 20 weeks at 0°C, showed that the collagen wrap adhered to the beef and
held in purge. The collagen-wrap showed anon-significant difference in the
moisture vapor transmission rate, and strength, in comparison to the plastic
which was used to wrap the controls (RICE,1994).
Incorporation of pork collagen at 0, 1, 2, and 3% in frankfurters and
restructured ham resulted in increased cooking yield for frankfurters, but
not for ham. Additionally,anincrease in the level of pork collagen decreased
the amount of purge in both of the products in adose-dependent
manner (PRABHU et al., 2004). Many reports show that the use of gelatin
coatings also reduces the amount of purge from meat products during
storage. Upon the storage of frozen pork bellies sprayed with a10% solution
of gelatin for 6, 12,and 18 months, there was loss of 1% less water than
the controls (MARGGRANDER and HOFMANN,1997). WHITMAN et al. (1971)
also reported the reduction in purge of fresh pork livers coated with a
solution of gelatin (20%) and propylene glycol (80%), stored under refrigerated
and frozen conditions. Dry sausages dipped into asolution of gelatin,
salt and water,and dipped into asecond solution of aSaran base, had a
relatively small weight loss at the end of the storage time (KEIL,1961).
ANTONIEWSKI et al. (2007) found that a20% bovine gelatin coating reduced
purge when it was applied to fresh beef and pork loins, chicken breasts,
and salmon fillets stored in an 80% O2 and 20% CO2 MAP, under 1050 lux
fluorescent light at 4°Cfor 1, 7, and 14 days.
Keeping the meat surface color
Color of fresh and/ or processed meat is of major concern to end users.
The color of the fresh muscle tissue is purplish-red (Fig. 4) as the iron in
deoxymyoglobin is in the ferrous state, Fe +2 ,and becomes bright red, when
exposed to oxygen; iron is oxygenated, or binds O2,and oxymyoglobin is
formed. With longer storage, the muscle-iron can become oxidized and
change to the ferric, or Fe +3 form. The metmyoglobin that is formed from
this oxidation is brown (Fig. 4). Substantial metmyoglobin formation
renders the product unattractive to consumers (GENNADIOS et al., 1997). A
decrease in redness is due to the increased formation of metmyoglobin on
the surface of the meat. MADHAVI and CARPENTER (1993) stated that when
there was a20% accumulation of metmyglobin in beef short loins, it was
no longer acceptable to consumers and was rejected.