Microstructural changes in hazelnuts during roasting

The microstructure of raw and roasted hazelnuts was investigated with light microscopy (LM). Tissue sections were fixed chemically using a mixture of formaldehyde, glutaraldehyde and buffer. Polyester was used as a resin. Thin sections were prepared by using a grinding method. Thermal changes in the microstructure developed gradually with increasing air temperature, air velocity and roasting time. Roasting led to some degree of cell wall separation and intercellular spaces, partial disruption of cytoplasmic network, swollen and aggregated protein bodies. These changes were observed in the microstructure of extremely liked quality of hazelnuts (roasted at 165 degreesC, 1 m/s. 25 min.). Due to the increase in the volume of intercellular spaces, crispness and crunchiness of roasted hazelnuts were increased

Determination of optimum hazelnut roasting conditions

The objective of this study was to test the hypothesis that the roasting conditions used for hazelnuts, such as the air temperature, air velocity and roasting time (independent variables), could be optimized by using Response Surface Methodology. Effects of independent variables on sensory and physical characteristics were determined. A consumer test was used to determine the acceptable samples. Very dark and very light roasted samples, corresponding to 165 degreesC, 3 m/s, 25 min and 125 degreesC, 1 m/s, 15 min process conditions, respectively, were unacceptable. Superimposed contour plots were used to determine the values of independent variables and these showed the process conditions where all product characteristics were acceptable to consumers. At low velocity (0.3 m/s), acceptable products were produced at about 165-179 degreesC for 20-25 min. When air velocity increased, air temperature shifted to lower temperatures. Samples roasted at 145 degreesC, 2 m/s, 28 min, 165 degreesC, 1 m/s, 25 min and 145 degreesC, 3.7 m/s, 20 min produced the most acceptable products. The sample roasted at 165 degreesC, 1 m/s, 25 min required the least air velocity and was the most economical in terms of energy consumed among the samples rated most acceptable by consumers

Mathematical modeling of survival and weight loss of Baker's yeast during drying

Drying and death rates of Baker's yeast were studied in a computer-controlled laboratory scale tunnel drier with varying air velocity between 2.0-3.0 ms-1 and temperatures within the range of 40-60 degrees C. Two falling rate periods were observed during the drying process. A single first-order expression described the death rate of the microorganisms during both drying phases. Arrhenius-type expressions described the effects of the temperature on the first falling rate period drying and death rate constants. Compensation relations were also found between the parameters of these Arrhenius expressions. A single linear relation was observed between the first falling rate period drying constant and the death rate constant at 2.5 with 3.0 m s(-1) for air velocity. A similar relation was also observed with the data obtained at 2.0 m s(-1) of air velocity. It was concluded that the death rate of yeast was lower with a slower air velocity