Designing cold dryer for producing dried meat product and determining the drying-quality characteristics of dried meat product

In this study, it was aimed to design a dryer that operates at low temperature for the production of a dried meat product that is minimally processed and does not pose a risk to food safety and to determine the drying and quality characteristics of the product obtained from this dryer. On this purpose, firstly a new dryer which can carry out minimal processing to the meat, provide food safety and perform drying in cold conditions (<20°C) was designed. Beef slices loaded in this dryer were dried at different low temperatures (10, 15 and 20°C) and air flow velocities (1, 2, 3 and 4 m/s) after pasteurization with hot steam and the drying and some physical, chemical, microbiological and sensory quality characteristics were determined. In addition, the sample group with high quality and sensory properties was reproduced and packaged in two different types of MAP (modified atmospheric packaging) and AP (atmospheric packaging) and stored at different temperatures (4 and 25°C). In order to determine the effect of different storage conditions; some chemical, microbiological and sensory analyzes were performed on samples at 0, 15, 30, 45, 60, 75 and 90 days of storage. When the effect of different drying conditions on drying kinetics of the samples was evaluated; moisture ratio (MR) values of beef slices were exponentially decreased with increasing drying time, the drying time increased with increasing temperature and decreased with increasing air velocity, average effective diffusion coefficient was 7.13x10-10 m2/s, activation energy was 44.96 kJ/mol, and the drying kinetics parameters were defined the best by Page model. When the effect of different drying conditions on the samples is evaluated; it was determined that the average moisture content of cold-dried beef slices was 40%, the water activity value was 0.89, the pH value was 5.74, the thiobarbituric acid reactive compounds (TBARS) value was 48.25 μmol MDA/kg and the non-protein nitrogenous substance (NPN-M) value was 4.26 g/100g. It has been determined that the effect of low drying temperature on the color values of beef slices was positive. It was found that the shear force value of the samples decreased from 49.54 N to 47.10 N with increasing temperature and increased from 46.45 N to 50.77 N with increasing air velocity. The microbiological quality of beef slices dried at low temperature and air velocity was higher and the mean total aerobic mesophilic bacteria (TAMB), total psychrophilic bacteria (TPB), Micrococcus/Staphylococcus, lactic acid bacteria (LAB) and yeast-mold counts were 3.18, 1.76, 3.00 , 1.88 and 2.37 log cfu/g, respectively. In sensory evaluation, it was determined that the samples dried at low temperature and high air velocity had higher quality and the samples dried at 10°C and 3 m/s had the highest score of overall acceptability. When the effect of different storage conditions on the samples is evaluated; as the storage temperature and time increased, it was determined that the amount of CO2 decreased in the MAP packed samples and that the amount of O2 decreased while the amount of CO2 increased in the AP packed samples. The water activity value of stored beef slices decreased from 0.91 to 0.88 during 90 days of storage. The pH, TBARS and NPN-M values of stored beef slices were higher in the AP packed samples and pH value increased from 5.68 to 5.93, TBARS increased from 25.25 to 60.11 μmol MDA/kg and NPN-M value increased from 4.37 to 6.66 g/100g during the 90 days of storage. It was determined that the microbiological quality of MAP packed samples was higher and the mean counts of TAMB, TPB, Micrococcus/Staphylococcus, LAB and yeast-mold were 4.10, 3.28, 3.46, 2.99 and 3.14 log cfu/g, respectively. As a result of sensory evaluation, it was found that the quality of samples packed MAP and stored at low temperature was higher and the shelf life of samples was 90 days at 4°C and 75 days at 25°C for MAP treatment, and 60 days at 4°C and 45 days at 25°C for AP treatment. When the research findings analyzed overall, it was concluded that beef slices could be dried in a cold medium with a minimal processing approach without the loss of their quality properties and stored with an acceptable shelf life in common packaging types.