Untersuchungen zur hygienischen und mikrobiologischen Qualität von marinierten Fleischzubereitungen zur Festlegung von Richtwerten bei der Kontrolle des Mindesthaltbarkeitsdatums (MHD)

Examinations concerning the microbiological and hygienic quality of
marinated meat preparations in order to determine guidelines to
control the best-before-date In this study 52 marinades, 5
seasoning mixtures and 1 lemon seasoning were surveyed at the time
of delivery and again following 4 weeks of refrigeration at + 6 °C
± 2°C. An analysis was also performed on self-made meat
preparations consisting of pork respectively venison marinated in
three different marinades. The marinated meat samples were produced
and examined in duplicate to increase statistical accuracy. The
examinations were carried out after 1 and 2 weeks of cold storage
and after 6 weeks of deep freezing in order to determine the
best-before-date of these self-service-products. The effect of an
interruption in the cold chain was also examined as follows: 3
hours interruption for cold storage products and 5 hours for frozen
products. This procedure was chosen to simulate the interruptions
occuring during transport from dealer to customer or from customer
to customer. All samples were examined in the following three
categories: sensory examination, microbiological survey, and pH
value. The sensory examination included “general characteristics”,
“external qualities”, “consistency”, “appearance”, “odor”, “taste”
and “haptic consistency”. Taste and haptic consistency were only
determined for the marinades and seasoning mixtures, as the
marinated meat could only be examined in raw condition and could
therefore not be analysed concerning taste. The microbiological
survey included the examination of total viable count, B. cereus,
Enterobacteriaceae, E. coli, C. perfringens, lactic acid bacteria,
coagulase-positive staphylococci and salmonellae. The pH-value was
measured by means of a pH-meter if possible. In the case of
oil-containing marinades the pH-value was determined using
pH-indicator paper. According to the sensory examinations, neither
the marinades nor the seasoning mixtures had to be rejected after
the initial examination nor after the 4 weeks storage. The high
intensity of taste can be explained by the very spicy character of
the concentrated marinades. The marinades are generally meant to be
used as a taste enhancing component in meat preparations and are
not intended for direct consumption. The sensory examination of the
marinated pork samples revealed a musty and odor compo-nent in 33 %
of the samples after 1 week and in 100 % after 2 weeks of cold
storage. According to sensory examinations 67 % of the samples were
eventually classified as spoilt after 2 weeks. Only 33 % of the
deep frozen samples were judged as musty and dull while none of
those samples was spoilt after 6 weeks storage. Such sensory
defects as a slimy and rope forming consistency were observed in 33
% of the samples after 2 and 6 weeks of storage, while 67 % of the
frozen samples showed separation of fat within the marinades. The
sensory examination of the marinated venison samples revealed that
17 % had a musty and dull odor after 1 week, increasing to 50 %
after 2 weeks of cold storage. In 33 % of the samples frozen for 6
weeks a musty and dull odor was observed. Putrid smell and spoilage
could be detected in 33% of the samples after 1 week, in 67% after
2 weeks cold storage and in none of the samples after deep
freezing. 33 % of the samples were slimy and rope forming after 1
as well as 2 weeks of cold storage. Separation of fat occurred only
in the frozen samples (67 % of the samples). No significant
differences could be observed between samples subjected to an
interruption of the cold chain and samples held at constant
temperature. The microbiological survey of the marinades revealed
no occurrence of pathogenic bacteria in critical amounts, with the
exception of the detection of B. cereus and C. perfringens in small
quantities. Both species of bacteria are to be considered
innocuous, because the marinades are subjected to heat treatment
together with the meat thereby destroying the toxins. Only the
emetic toxin produced by B. cereus is heat resistant and could be a
threat to the consumer. In general, the total viable count in
marinade samples obtained from containers used in the production
process of self-service-products was higher than that of the
samples taken directly out of the marinade producers’ original
packing. In marinated pork the number of microbes was relatively
high in comparison to the untreated meat. The increase in microbes
can be attributed to suboptimal conditions in manual processing of
the meat preparation. In industrial processing under optimal
hygiene circumstances an expiration date of 1 week to 10 days can
be justifiable. The microbiological results of deep freezing
suggest that this method can be regarded as a viable alternative
for ensuring longer storage life and better quality. The
examination of raw venison already yielded critical results with
regard to its suitability for meat preparations used for
barbecuing. The examination of marinated venison further
strengthened those results. Only as frozen product a suitable
quality could be guaranteed for a longer period because most
microbes do not survive a deep freezing process. The pH
measurements did not provide any indication of the grade of
spoilage. Only after 2 weeks of cold storage a slight decrease in
pH was observed, which might indicate progressive spoilage.
Generally, the increase in microbiological counts correlated with
sensory defects and the duration of storage. Yet the number of
microbes showed a slightly earlier and more noticable rise than was
to be expected based on the sensory examinations carried out in the
same time period.