a. pourfarzad

 Marinated chicken meat is one of the traditional foods in Iran which is an indoor and outdoor popular food in different areas of Iran due to its convenience and pleasant taste. It is also one of the authentic foods which is categorized in Iranian traditional kebabs. This product is constituted of fresh pieces of chicken meat, diced in different pieces, marinated with salt, lemon juice, verjuice, vegetables, saffron, spices, fruits and oil and then supplied as fresh and/or frozen form. After the seasoning, it is grilled using a skewer. Therefore, it is necessary to investigate its microbial load, shelf life, and quality changes during storage. To the best of our knowledge, there are no reports on the chemical and microbial properties of processed chicken meat used as a factor to predict its shelf life. Thus, the present study was designed to examine the relationship between physicochemical, microbial and sensory properties of the marinated chicken meat during storage using symmetric multivariate (determination of correlation coefficients and principal components analysis) and asymmetric methods (partial least squares regression).

 In this study, 30 samples of marinated chicken meat were collected from restaurants. Then, the asymmetric method (completely randomized factorial and partial least squares regression) and symmetric method (coefficients of determination and Principal components analysis) were used for the study of chemical (aw, TVN, pH, O/R) and microbial (total count, Staphylococcus aureusand Escherichia coli) and organoleptic characteristics of samples on the storage days of 0, 3, 6 and 9.An aw meter was used to measure the aqueous activity (aw), an automatic Kjeldahl device was used to measure total volatile nitrogen (TVN) and a pH meter was used to measure pH and redox potential (O / R). The dilution method was used to count the total bacteria. The cooked meat and bird parker media were used to identify Staphylococcus aureus. The MPN method was used to identify Escherichia coli. Sensory evaluations were carried out by 10 trained panelists. All assessors of the internal sensory panel assumed the basic odor test and color vision test. Each sample contained 50g marinated chicken meat, which was given to panelists in plastic containers at room temperature. The color, odor and overall acceptance of the marinated chicken meat were assessed. Each evaluator randomly evaluated the samples and served drinking water before each evaluation. Each parameter was scored in a 5-point scaling ranging from 1 (lowest) to 5 (highest). The data on the physicochemical, sensory and microbial properties of marinated chicken meat were statistically analyzed using Minitab 15 software (Minitab Inc., State College, PA, USA). The mean values of the treatments were compared by Duncan's multiple range test at a confidence level of 95%. Each experiment was performed in three replications. The PCA and PLSR modeling were also performed on the datasets.

 Results from the statistical analysis suggest that the microbial and chemical parameters of marinated chicken meat were greatly capable of predicting its shelf life. Determination coefficients, principal components analysis (PCA), and partial least squares regression (PLSR) models are able to extract relevant information and offer an easy and promising approach for the interpretation microbial and chemical properties of samples and their correlation with shelf life. The obtained results indicated that three parameters including pH, redox potential and total count had the highest correlation with shelf life, recommended as the predictive components. The results of measuring water activity in chicken meat samples during storage at refrigerator temperature showed that the aw parameter did not change significantly during storage time in the samples while the pH, TVN and O / R parameters were significantly affected. Changes in the total count, Staphylococcus aureus and Escherichia coli were also significant during refrigeration. Sensory evaluation experiments showed that all samples had no signs of spoilage until the sixth day.

The obtained results indicated that three parameters including pH, redox potential and total count had the highest correlation with shelf life, recommended as the predictive components. Overall, we can produce a product with higher quality and shelf-life if high quality raw materials are supplied with suitable pH values and also, hygienic production is considered.

Doogh is one of the traditional drinks in Iran and yeast is the original reason of its spoilage. In this research, propolis (a product of bee) was used for preventing the yeast growth in unpasteurized doogh. The polymerase chain reaction (PCR) method was used to diagnose the yeast that caused spoilage (Kluyveromyces marxianus). Water, glycerol and ethanol were used as solvents to extract phenolic compounds of propolis. According to extraction efficiency, capability of usage in food products and results of MIC and MBC tests, glycerol extract has been selected for Doogh examinations. The effect of 1.5, 3, 4.5, 6% of glycerol extract on pH, titratable acidity, DPPH, decreased yeast count and sensory properties of unpasteurized Doogh during storage at temperatures of 5 and 25°C. Results revealed that 3% glycerol extract of propolis, decreased yeast during storage at both temperatures of 5 and 25 °C without any negative effect on sensory parameters, for two and more than fourteen days, respectively. Also, total yeasts significantly decreased with increasing the glycerol extract of propolis (P<0.05). Furthermore, the DPPH was not affected during storage at both temperatures. Using the propolis extract in unpasteurized Doogh resulted in the prevention of yeast caused spoilage and specially production of a functional food containing high amounts of antioxidants.