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.
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