بهینه‌سازی فرآیند تولید قرص فشرده گوجه‌فرنگی بر مبنای ویژگی‎های فیزیکی، مکانیکی و حرارتی در شرایط هوای گرم با پیش تیمار مایکروویو

در این پژوهش اثر متغیرهای خشک‌کردن به شیوه هوای ‌گرم با اعمال پیش تیمار مایکروویو شامل دمای هوا، سرعت هوا و مدت زمان مایکروویو بر ویژگی‌های فیزیکی (چروکیدگی و چگالی واحد)، مکانیکی (مقاومت به نفوذ) و حرارتی (ضریب انتشار موثر رطوبت و انرژی مصرفی خشک‌کردن) قرص فشرده تولید شده از پودر گوجه‌فرنگی مورد بررسی قرار گرفت. فرآیند خشک‌کردن نمونه‌ها در پنج سطح دمایی 40، 50، 60، 70 و °c80، پنج سطح سرعت هوا 0.5، 1، 1.5، 2 و m/s 2.5 و پنج زمان مختلف فرآیند مایکروویو صفر (بدون اعمال مایکروویو)، 4، 8، 12 و s 16 در توان ثابت w 90 صورت گرفت. تجزیه و تحلیل آماری داده‌ها و بهینه‌سازی فرآیند خشک‌کردن با استفاده از روش سطح پاسخ انجام شد. نتایج نشان داد که استفاده از پیش تیمار مایکروویو سبب کاهش زمان خشک‌کردن و انرژی مصرفی آن و همچنین اثر معنی داری بر بهبود خواص فیزیکی و مکانیکی قرص های فشرده تولید شده داشت. افزایش دمای هوای خشک‌کردن بر ضریب انتشار موثر رطوبت و چروکیدگی اثر مثبت و بر انرژی ویژه مصرفی خشک‌کردن، مقاومت به نفوذ و بر چگالی واحد اثر منفی داشت. با افزایش مدت زمان مایکروویو مقدار ضریب انتشار موثر رطوبت افزایش و با کاهش آن مقدار چروکیدگی محصول کاهش یافت. نقطه بهینه خشک‌کردن قرص فشرده تولید شده از پودر گوجه‌فرنگی در دمای °c50، سرعت هوا m/s 1 و مدت زمان مایکروویو s 4 به‌دست آمد. خشک‌کردن تحت شرایط کمترین دما (°c40) وکمترین زمان مایکروویو (s 4) سبب بهبود خواص فیزیکی و مکانیکی قرص فشرده گردید.

Optimization of tomato compressed tablet production based on physical, mechanical and thermal properties in a hot air condition with microwave pretreatment

Introduction: Tomato is one of the most valuable sources of minerals and vitamins supply in the human diet. Low shelf life of tomato and its short shelf life with inadequate processing facilities lead to heavy financial losses. Therefore, preserving and processing of tomato are of the commercial importance. Drying is one of the preferred methods for tomato preservation. Dried tomato products including half tomatoes, tomato slices and tomato powder, have many consumptions, compared with other tomato products. Among dried tomato products, tomato powder has a particular market. Powder production is an alternative method to extend the shelf life of foods. Usually the fruit powder is very dry, humidity absorber and has too much volume. Therefore, during storage, transportation and administration, it requires special care and heavy packaging which increase the cost. To overcome these problems, compression of the fruit powder in tablet form could be a proper solution. Tablet making of fruit powder has gained much popularity due to its ease of use, storage, transportation and product formulation. After the tablet making process, the pills contain high moisture contentwhich makes them unsuitable for transportation and storage. So, in order to prevent the tablets corruption and maintain their quality, tablet drying is one of the important steps after the tablet making process. The drying process is an important operation that affects the quality and final price of the product. Different drying methods play an important role in protecting foodstuffs. However, the effect of different drying methods on the quality of some foodstuffs is not clear.;  ;Materials and methods: In this research, after the preparation of fresh tomatoes, the primary moisture content of tomatoes was determined using hot air oven method. Then, using blanching method, the tomatoes were peeled and samples were cut using a sharp razor in thicknesses of 3 mm. Tomato slices were dried using a semiindustrial dryer in a hot air at 50 °C at an air speed of 1 m/s. Dried tomato slices were powdered using a grinder. In order to homogenize the particle size, the tomato powder was sieved by a 50 mesh (Cavity size 0.5 mm) sample. Suitable moisture content to create sufficient adhesion between the particles of tomato powder was selected at %23 d.b. Water and fructose were used as a bonding agent. The process of producing tomato spherical tablets was performed by a hydraulic press. Drying tests of wet compressed tablets were performed immediately after the end of the tabletting process using a hot air drying machine with microwave pretreatment. In this study, the effect of drying variables,through using of  microwave pretreatment along with hot air, including air temperature in five levels (40, 50, 60, 70 and 80 °C), air velocity at five levels (0.5, 1, 1.5, 2, and 2.5 m/s) and the duration of microwave application at five levels (zero (without microwave), 4, 8, 12, and 16 s) on physical properties (shrinkage and unit density), mechanical (penetration resistance) and thermal (Effective moisture diffusivity and energy consuming drying) of compact pomegranate produced from tomato powder were studied. Statistical analysis of data and optimization of drying process were performed using response surface method and central composite design.;  ;Results and discussion: Results showed that effect of air temperature and duration of microwave pretreatment on all variables of compressed tomato tablets were significant in hot air dryers with microwave pretreatment. Increasing temperature and time of microwave pretreatment increased the effective moisture diffusivity and shrinkage of the final product. The temperature of the air inlet to the dryer had a negative effect on the resistance to penetration, the unit density and the specific energy consumption of the drying process. Drying under lower temperature conditions and less time for microwave pretreatment resulted in an increase in the desirability of the drying process