Browsing by Subject "Rindfleisch"

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Analysis of aging-related changes and influencing factors on the metabolome of beef
(2023) Bischof, Greta; Gibis, Monika
Aging of beef is necessary to improve its flavor and tenderness. There are two most common aging types, dry-aging and wet-aging. Dry-aged beef is often associated with a higher eating quality than wet-aged beef. The term “dry-aged beef” is not legally defined, so authentication methods are needed to protect the consumers from food fraud. During beef aging, the metabolome of beef changes due to the postmortem metabolism. This dissertation focuses on the aging method as a postmortem process and the resulting changes in the metabolome. As a hypothesis of this study, it was postulated that the detection of these metabolic changes due to aging of beef is feasible by 1H NMR spectroscopy and based on these measurements the evaluation of an authentication model for the aging method of beef is possible. In order to test this hypothesis, a sample preparation and measurement method was developed and based on this, potential influencing factors such as sampling position in muscle, breed and sex were investigated on the metabolome of fresh and aged beef. In the first part of this thesis, the sample preparation and the 1H NMR measurement method were developed. In the sample preparation, the polar fraction of the metabolome was extracted from 200 mg of beef, allowing 24 samples to be prepared in parallel. The sample preparation and the measurement method were validated, and the first aged beef samples were analyzed to check if the aging-related changes in the metabolome could be detected by this method. In the second part of this thesis, the sampling position in the muscle were analyzed for changes or differences in the metabolome due to its location in the muscle. The results showed that the metabolome changes along the length of the M. longissimus thoracis et lumborum, but the influence of the aging type and aging time was more pronounced in the metabolome of beef. The comparison of the surface and the inner part of wet-aged and dry-aged beef showed that the metabolome of dry-aged beef differed greatly between the surface and the inner part, despite the exclusion of the moisture content by freeze-drying and the low microbial load. There were only slight differences between the surface and the inner part for wet-aged beef, which could be due to the influence of microbiota and their metabolites. Therefore, the sampling location in the M. longissimus thoracis et lumborum was determined as precisely as possible for the further studies. The muscles were cut into ten pieces from cranial to caudal and dry-aged or wet-aged for 0, 7, 14, 21, and 28 days, in duplicates. The third part of this thesis focuses on the potential influencing factors such as breed and sex of the animals. Fresh and aged beef samples from three cattle types (heifer, cow, and young bull) and two different breeds (‘Fleckvieh’ and ‘Schwarzbunt’) were analyzed by targeted and non-targeted 1H NMR spectroscopy. Both factors were shown to influence the metabolome of fresh and aged beef. Therefore, these factors had to be included in the authentication model based on both targeted and non-targeted model. The calculation of the authentication model was the main part of this thesis and showed a good prediction of cattle type, breed, aging time and aging type of beef. The authentication model was based on the combination of multiple models of PLS-R and PLS-DA. The model for predicting the cattle type showed an accuracy of 99 %, and the models for predicting the breed depending on the cattle type showed an accuracy of 100 %. Aging time could be predicted with an error of 2.28 days. The statistical models for aging type were separated by aging time based on the determination of aging time. The model for predicting the aging type of 28-day aged samples had an accuracy of 99 %. The other statistical models for predicting aging type were additionally separated by cattle type and breed, and their accuracy ranged from 90 % to 100 %. In conclusion, an authentication model to determine the cattle type, breed, aging time and aging type of beef was developed in this dissertation. Therefore, it is possible to authenticate beef samples using a single 1H NMR spectrum. In future studies, it would be useful to extend this authentication model to other samples of other breeds and influencing factors.
Process, structure and function relationship in ground meat
(2023) Berger, Lisa Marie; Weiss, Jochen
Ground beef has enjoyed high popularity with consumers because it is convenient to use and facilitates a rapid preparation of a large variety of different meals. In the production of ground meat, the particle size of the meat is systematically reduced, and the cell structures are partially disintegrated. Ideally, the original cellular meat or fat structure is preserved as much as possible so that important quality attributes are optimized. However, the effect of varying conditions and parameters in modern processes on the quality of ground meat has not yet been investigated in detail. According to the current German “Leitsätze für Fleisch und Fleischerzeugnisse”, hamburgers must not contain more than 20 Vol.% of non-intact cell structures to be sold without further declaration. Therefore, this work aimed to identify process, structure, and function relationships in ground meat production to facilitate a gentler processing of in particular hamburgers. To investigate these effects systematically, a standardized production method for hamburgers was developed and a pilot plant scale meat grinder was set up with the possibility to record process-relevant data. The relationship between the structure and functionality of ground meat was investigated using a model system with increasing amounts of added meat batter to simulate changes in meat structure due to cell disintegration. A new term, i.e., the amount of non-intact cells (ANIC), was introduced to quantify the amount of disintegrated meat cells during processing. It was shown that changes in the structure due to a higher or lower ANIC resulted in altered physicochemical and functional properties of the ground meat system. The effect of frozen meat content and temperature on the structure and function of hamburgers was investigated to verify the above-obtained correlation to an application-relevant setting. As the specific cutting resistance is significantly higher in frozen than in chilled meat, it was assumed, that the impact on the ground meat’s structure and function differed accordingly. Indeed, this could be verified. In hamburger manufacturing, it is common practice to re-fed imperfectly molded patties, e.g., in a frozen, coarsely crushed state. In contrast to those findings, the use of up to 20 % re-fed material in hamburger manufacturing did not result in any noticeable differences as neither the specific mechanical energy input (SME) nor the ANIC was significantly changed. It was thus demonstrated, that some raw material variations can have an impact on both structure and function of hamburgers. Especially, temperature effects and associated changes in the cutting resistance of the raw material had the strongest influence on structure and function of ground meat. However, if structural differences were found, they were not sufficient to manifest in differences in sensory evaluation. This means that the consumer perception and thus the quality of the hamburger was not influenced. The process parameters and their impact on the structure and function of hamburgers were studied by investigating the impact of the four main processing steps pre-grinding, mixing, grinding, and forming. An increased ANIC was determined with progressive processing, whereby the grinding steps accounted for the strongest increase. Mixing and forming were of minor importance for structural and functional changes. By varying the cutting set parameters, the influence of the cutting set compositions on the structure and function of hamburgers was assessed. The SME and the ANIC increased if more cutting levels were used due to higher shear stress applied to the meat. However, the hole plate properties did cause no or only negligible changes in the ANIC and SME. Although an impact of the cutting set composition on the structure could be found, no or only marginal effects on the function and the sensory and optical quality of the hamburgers were found. It can therefore be concluded that the shear forces acting on the meat during grinding have the strongest influence on the structure and function of beef. By reducing the acting shear forces, the grinding can be designed to be gentler resulting in lower ANIC. Despite the influence on the process-control (SME, pressure, torque) and the structural parameters (ANIC), it needs to be emphasized that the influence on the function and quality of the hamburgers is small in application-relevant ranges. In application-relevant ranges this relationship is only slightly pronounced. Comparable results were found, as raw material variations only partially caused structural, functional, and quality effects in the hamburgers. This in turn means that changes in structure cannot always be linked to a shift in perceived quality. In order to carry out an integrated evaluation of the product, structural parameters and quality parameters must be defined, assessed separately, and merged into a combined overall sample assessment.