Stefanie Retz

Effect of maturation and freezing on quality and drying kinetics of beef

ABSTRACT The quality of dried meat products and their drying kinetics significantly depends on the status of the raw material going into the drying process. The aim of this study was to determine the impact of meat status (fresh, mature, frozen–thawed) on the drying kinetics and the resulting quality in terms of color changes and spectrally deductible information. Drying tests were conducted using meat from organically raised bulls. In the fresh meat, freezing leads to a decrease in the drying rate, while for matured meat, the opposite is true. Aging and freezing have little effect on the end product quality in terms of final product color. However, water content can be detected hyperspectrally and resolved spatially for all stages of the process. With regard to water content prediction, the Monte-Carlo uninformative variable elimination-partial least square method performs best for the fresh and fresh frozen–thawed version with seven wavelengths, an r2 of 0.97 and 0.88, and RMSE (Root mean squared error) of 0.15 and 0.17 for the test set, respectively.

Drying behavior and quality parameters of dried beef (biltong) subjected to different pre-treatments and maturation stages

ABSTRACT The drying behavior of fresh, matured, and frozen beef, marinated with 0.5% salt, 1% salt, salt and vinegar, and blind samples, dried at 70°C, was investigated. Weight and color (CIELAB) were measured and images of the samples were created with a hyperspectral imaging camera. Results show that the marinade and the type of beef influences the drying behavior of beef, but not the final color. Results from the hyperspectral imaging show that it is possible to build good fitting prediction models resulting in high R2 (min. 0.81, max. 0.98) and low RMSE (min. 0.08, max. 2.35) for moisture content, a* and b* values.

High pH thresholding of beef with VNIR hyperspectral imaging

Initial quality grading of meat is generally carried out using invasive and occasionally destructive sampling for the purposes of pH testing. Precise pH and thresholds exist to allow the classification of different statuses of meat, e.g. for detection of dry, firm, and dark (DFD) (when dealing with cattle and sheep), or pale, soft exudative meat (when dealing with pork). This paper illustrates that threshold detection for pH level in beef with different freshness levels (fresh, fresh frozen-thawed, matured, and matured frozen-thawed). Use of support vector machine (SVM) analysis allowed for the classification of beef samples with a pH above 5.9, and below 5.6, with an accuracy of 91% and 99% respectively. Biochemical and physical conditions of the meat concerning the pH are discussed.

Stress-free slaughter of outdoor cattle

During the last decades, many improvements regarding transport conditions, preslaughter handling and stunning of cattle at commercial abattoirs have been developed but still a lot of difficulties do occur. Especially animals not accustomed to human-animal contact, such as frequently the case in free range beef cattle, can be even more challenging to handle at the day of slaughter. In 2011, free-bullet rifle shooting has become an allowable on-farm slaughter method for outdoor cattle in Germany. To enhance free-bullet rifle shooting to become a more professional method is the superior aim of our studies and certain practice recommendations could already be concluded. Our recommendations are mainly based on four studies of a pilot project, which are partly under evaluation and partly ongoing. The first study is aimed at gaining information about the effectiveness of different types of weapons and ammunition. Isolated heads of post-mortem cattle (German Angus, Galloway and crossbreeds, total n=44) were shot in different ways and sections of the skulls were done, focusing mainly on the shot location, shooting angle, penetration depth and transformation of the bullet as well as on the penetrated brain tissue. In the second study, live cattle (German Angus, Galloway and Highland Cattle, total n=31) were shot according to the results of the first study while behavioural observations and video monitoring have been done. To control stun quality, the same pathological recording as in the first study, but also including brain haemorrhages, was performed. The third and fourth studies (ongoing) focus on key parameters of meat quality and on behavioural signs of pre-mortal stress, respectively. One group (Galloway, n=50) gets slaughtered by using the free-bullet rifle shooting method compared to another group of the same herd (n=50), slaughtered ordinarily at the abattoir (captive bolt stunning). However, free-bullet rifle shooting of outdoor cattle might be a solution for completely stress-free slaughter on certain farms willing to fulfil all the requirements. Most attention has to be paid to the shooter’s capabilities.

Mechanische Reinigung von Spaltenböden

Die Reinigungswirkung eines Spaltenboden-Reinigungsgerats wurde unter Praxisbedingungen in einem Milchviehstall und in einem Versuchsstand getestet. Dabei wurden neben einem herkommlichen Spaltenschieber auch Raumsterne, welche die Spaltenzwischenraume freilegen, sowie eine Hochdruckreinigungsvorrichtung mit Wasser betrachtet. Zur Beurteilung der einzelnen Reinigungsschritte wurde auf einem Versuchsstand das Reinigungsgerat nachempfunden und die einzelnen Reinigungsschritte individuell untersucht. Die maximale Reinigungswirkung lasst sich erreichen, wenn die Tiere tagsuber auf der Weide sind und der Spaltenboden abtrocknen kann. Eine Hochdruckreinigung eignet sich dann, wenn Kot auf den Spalten noch nicht festgetrocknet ist.