شهین شرافت خواه آذری

Owning to drawbacks of synthetic polymers, biodegradable packaging materials (biopolymers) have received more attention both in studies and industrial applications. However, compared to conventional packaging, the biodegradable materials have some limitation must be eliminated either by using composite preparation method or introduction of nanotechnology. Inclusion of metal nanoparticles and their oxides are of the new approaches to improve the properties of packaging films. Therefore, the present study attempted to investigate the effect of ZnO (0, 2.5 and 5%) and β-glucan (0, 10 and 20%) incorporation on chemical and microbial properties of gelatin based biodegradable film over storage of chicken fillet. Results showed that incorporation the both of ZnO and β-glucan have significantly (p<0.01) improved the barrier properties against both of moisture absorption and water vapor permeability and the best properties obtained with film containing 5% of ZnO and 20% β-glucan. In addition, based on microbial tests result, it was obvious that the ZnO loaded films have antimicrobial properties and the highest inhibition activity obtained with 5% of ZnO against the all of studied pathogenic bacteria. Accordingly, the film containing 5% ZnO and 20% β-glucan is introduced as the most effective film for packaging of chicken fillets.

Osmotic drying process is using of hypertonic solution (osmotic) for the disposal of water in the product. In this study, optimizing in the drying of strawberry was investigated based on chemical and sensory properties. Water loss (%WL) and solid gain (%SG) were used to choose of the best treatment to produce of dried strawberries during 5 hours and at 1, 2, 3, 4 and 5 hours by different osmotic solutions at two different temperatures. The used treatments were including of different osmotic solutions and different content of calcium chloride (%0.75 and %1.5) at 35°C and 45°C. The results showed that the best treatment among the eight different treatments was the treatment 8 (osmotic solution containing 50% fructose and 20% sucrose, 1/5% calcium chloride and treatment time of 5 hours at 45°C) which made to the better drying of strawberries in compared with the other treatments. Moisture content (%28 and %88), pH (3.55 and 3.15), acidity (% 0.043 and % 0.053), Brix (%24and %6), total sugar (%14.5 and %4.5), vitamin C (9 and 25.5mg/100 g) and Anthocyanin (75.5 and 102.75 mg/kg) were in the strawberry samples dried by osmotic method and the control, respectively. Moreover, sensory properties of osmotic dried strawberries including, appearance, color, firmness and flavor were better in comparison to control sample.

n this study, the effect of different drying methods was investigated on physicochemical characteristics, sensory properties and nutritional quality of strawberry and effective factors on the increasing of its shelf life. For osmotic dehydration treatment, temperature (35 and 45 °C), mixture of fructose and sucrose syrup concentration (70%(W/V) (20% fructose 50% sucrose)), calcium chloride (0.75 and 1.5% (W/V)), during 5 hours with 1 to 8 ratio of fruit to osmotic solution was used. The best treatment among the 8 different treatments was the treatment 8 (osmotic solution containing %50 fructose with %20 sucrose %1.5 calcium chloride and treatment time of 5 hours at 45°C) with respect to the lowest SG/WL which lead to better drying of strawberries in comparison with the other treatments and was known as the best treatment. Then, the best osmotic treatment with respect to physicochemical characteristics, and sensory properties was evaluated and compared to dried strawberry samples by microwave, hot air oven and control sample. The results showed the moisture content (%28, %37 and %18), pH (3.57, 3.15 and 3.19), acidity (% 0.042, %0.045 and % 0.044), Brix (%23, %15 and %26), total sugar (%15, %4 and %3), vitamin C (8, 13 and 19mg/100 g) and Anthocyanin (75, 72 and 86 mg/kg) in the strawberry samples dried by osmotic method, hot air oven and microwave methods, respectively. Dried strawberries using the microwave had lower moisture content, total sugar and a higher brix, vitamin C and anthocyanins than the samples dried with osmotic and hot air oven methods. On the other hand, from the viewpoint of sensory properties, dried strawberry using microwave and osmotic methods had better appearance, color, firmness and flavor in comparison with dried samples by hot air oven and control. Overall, dried strawberries using the microwave method had the lowest amount of moisture, vitamin C and the higher content of anthocyanins and sensory characteristics than the other drying methods. Therefore, in this study for producing of dried strawberries in comparison with the other drying methods, the microwave method was recommended.