جستجوی مقالات مرتبط با کلیدواژه « Pear » در نشریات گروه « صنایع غذایی »

The efficiency of several theoretical models to predict the moisture content of pear slices during drying were evaluated and compared. Pear slices were dried at 5 different temperatures (30-40-50-60-70oC) and the moisture diffusivity and convective mass transfer coefficient were estimated. In the next step, mass transfer model was developed by using mathematical solution of Fickchr(chr('39')39chr('39'))s second law of diffusion with different numerical and analytical models. The results of the studied models indicated that the both numerical models were substantially more accurate than analytical model in describing the experimental drying curves. However, the best result was obtained with the combined model developed in this study. This model presents the highest coefficient of determination (R2) value (0.999), and the lowest root mean square error (RMSE) value (0.06). The higher accuracy of this model can be attributed to the fact that this model takes into account the term that simulate the convective moisture transport and chooses the appropriate boundary conditions. By applying this model, it is possible to predict moisture variations in pear slices with high accuracy as a function of internal variables (thickness, chemical composition) and external factors (temperature, relative humidity and air velocity).

By controlling dehydration and rehydration conditions, optimal reconstitution properties can be achieved. Therefore, mathematical models that describe the kinetics of moisture removal and moisture uptake are important in designing and optimizing that process. In this study, the drying process of pear slices at 5 different temperatures was investigated and the effective diffusion coefficient of the samples was determined. Drying data were also fitted with 9 mathematical models. The hydration process of the dried samples at 50°‌C was also fitted with 4 different models. The results showed that the effective diffusion coefficient has an increasing trend with increasing temperature and its temperature dependence can be described by Arrhenius equation. Among the dehydration models, two models (logarithmic and Weibull) were better than other models in predicting changes in sample moisture during drying and the best model for the rehydration process was Peleg model. In the last step, the temperature dependence of the constants of these equations were fitted with Arrhenius and exponential decay models.

In this study effect of temperature, O2 concentration and storage time were investigated on respiration rate of uncoated and coated pear (Dargazi Cultivar) using Sclerorhachis platyrachis essential oil of 0, 125, 250, and 500 ppm. Mathematical model using Michaelis–Menten’s equation, with the model constants described by means of an Arrhenius-type relationship was applied to predict respiration rate at various temperatures (4, 10, and 25 ºC) and O2 concentrations to design modified atmosphere packaging (MAP) of pear in order to extend its shelf-life. Results showed that all factors affected respiration rate of the pears but the influence of temperature was most pronounced. Increase in temperature led to increase of respiration rate and reduction of positive effect of essential oil on this parameter reduction. Moreover, after about 100 hours, respiration reached equilibrium. Respiratory quotient of Pears at 4 and 10 °C was on aerobic limit. However, at 25 °C, after 110 hours, and reaching CO2 to 23%, respiratory quotient passed the critical point. Finally, package containing 3.7% O2 + 8.1% CO2 + 88.2% N2 was suggested as an appropriate MAP for storing the pears (Dargazi cultivar).

The study of the relationships between physical properties such as mass, volume and size of fruits is very important.In this research via CT scan, the relationship between physical properties of pears and storage times with bruise due to the loading force was investigated. Before loading and storing, 50 pears were examined using CT scan and 27 pears with zero bruise percentage were selected. Dimensions of pears (length, width, thickness) were measured, then properties such as the equivalent diameter, geometric mean diameter, spherical coefficient, surface area and aspect ratio of calculus were calculated, then selected pears were subjected to quasi-static loading with a thin edge pressure with three forces of 70, 100 and 130 N and 5, 10 and 15 d storage was used to investigate the effect of forces on pears. Then, after loading and storing, using the CT scan in each period of storage, the rate of pear bruise was calculated. The results of the experiments showed that there is an inverse relation between geometric diameter, arithmetic and equivalent diameter, spherical coefficient and aspect ratio with the bruise percentage. Also a direct and unreasonable relationship between the level of the surface area and the percentage of bruising. Overall, it was found that, the pears have a higher surface area, the higher the percentage of a bruise.

The study of relationship between physical properties such as mass and volume and other physical properties, such as geometric dimensions, has been the subject of numerous studies by researchers. The fruit size, shape and mass are important in sorting and measuring fruits, and it determines that the fruits can be put in boxes of transport or plastic bags by a specific size. Damage to the fruit may be due to various causes, including Impact, pressure and vibration, all of which cause physical damage at moment or at storage time, the amount of damages depends on location of impact, the size and volume. Also, the volume and physical properties of agricultural products are very important for storage. On the other hand, cell damage and forces involved in fruits reason bruising in fruits, which can be controlled by physical properties. Quality assessment is usually carried out using a combination of destructive and non-destructive methods, generally done by the product manufacturers or the first purchasers, and includes the separation of materials based on specific size and weight. Among non-destructive methods used, the use of CT and X-rays, which allow a person to examine bruises at different times in the fruit, is increasing. Due to the fact that mass and volume of fruits for storage, transportation, packaging and etc are of great importance, in this research, the relationship between pear fruit volume and mass with bruise percentage during the storage period was studied using non-destructive CT scan tests due to dynamic loads. Firstly, the pendulum and the required masses were made in a workshop. The fruits were placed in the desired position and then the device arm was raised to the desired angle (90°), and in the controlled state of the arm impact the pear. The pendulum had a 200 g and three different attachment masses of 100, 150, and 200 g for knocking. It should be noted that air resistance and friction were neglected through this procedure. In this research, via CT scan, the relationship between mass and volume of pears (Before and after the impact) due impact loading and storage times with bruise was investigated. Before loading and storing, 50 pears were examined using Scan CT and 27 pears with zero bruise percentage were selected, the next chosen pears were subjected to impact loading with a pendulum with three weight of 300, 350 and 400 g and 5, 10 and 15 days storage was used to investigate the effect of impact on pears. Then, after impact and storing, with the use of CT scan in each period of storage, the rate of pear bruise was calculated. The pears volume before impact with the bruise percentage for all three weights had a negative and non-significant correlation and the decrease pear mass percentage with the bruise percentage for all three weights has a positive correlation and pears mass before impact with the bruise percentage for all three weights had a positive and non-significant correlation. Any decrease in pear mass percentage had a positive correlation with caries percentage for all three weights. The correlation test showed that with the increase in pear volume, the bruise percentage was decreased and a direct correlation was found between the decreasing percentage volume and the bruise percentage. –also The effect of 5-day storage duration was found considerable on the bruise percentage subject to the exertion of 350 g and higher impact  rates

Drying of agricultural and horticultural crops is one of the most important processes for their long term storage. Therefore, in this study, the influence of drying temperature and air flow velocity on the variation of color, shrinkage and pH were investigated during the drying process of thin-sliced Dargazi pear varieties. Drying air temperature varied in four levels of 50, 60, 70 and 80 °C and the air flow velocity at three levels of 0.5, 1 and 1.5 m/s. The image processing results indicated that maximum variation of the sample’ color (30.78) occurred at drying temperature of 80°C and air velocity of 1.5 m/s. In contrast, the minimum variation of the color (14.38) occurred at drying temperature of 50 °C and air velocity of 0.5 m/s. The results indicated that PH of the examined samples increases during the drying process. The maximum value of pH (4.49) was obtained at drying temperature of 50 °C and air velocity of 0.5 m/s, whereas the minimum value (3.93) was measured at 80 °C and air velocity of 1.5 m/s. Given the overall results obtained in this study, minimum drying time with minimum variation of qualitative specifications occurred at drying temperature of 70 °C and air flow velocity of 0.5 m/s; therefore, this condition could be suggested as the best combination for drying of thin-sliced pears.

Osmotic treatment is based on placing foods into a hypertonic solution that has higher osmotic pressure and lower water activity than the foodstuffs. Food dehydration process in several reasons, causes deteriorate qualitative characteristics in final products. So it is necessary to use some pretreatments such as osmotic dehydration. The Major limitation with commercial production of osmotically dehydrated products is the high solid uptake by the texture and lack of proper management of osmotic solutions. Use of edible coating with reused of solution is important. In this research, during osmotic dehydration of pear rings, the effects of concentration of sucrose solutions of 50 percent (w/w), the CMC 0.5 percent (w/w), as in edible coat, in constant temperature of 30ºC, and reconstitution of osmotic solutions (until 5 times), were investigated on mass transfer phenomena including of the water loss (WL), solid gain (SG) and productivity ratio (WL/SG) of osmotic process. The result showed that use of edible coat and reconstituted osmotic solutions, increases the productivity ratio of process. The results present the osmotic coated samples were obtained after 5 times reconstitution of osmotic solution, as the superior samples.

Overall quality and shelf life of fruits and vegetables is reduced by several factors including water loss, enzymatic browning, texture deterioration, senescence processes and microbial growth. In the case of fresh-cut fruits, these events are accelerated due to wastage of tissues inflicted by peeling, slicing and cutting. Edible coatings have been used to reduce the deleterious effect brought about by minimal processing. The semi-permeable barrier provided by edible coating is aimed to extend shelf life by reducing moisture and solutes migration, gas exchange, respiration and oxidative reaction rates, as well as suppress of physiological disorders on fresh-cut fruits. Edible films and coatings can also offer a possibility to extend shelf life of fresh-cut produce by providing a semi-permeable barrier to gases and water vapor, and therefore, reducing respiration, enzymatic browning. Their protective function may be also enhanced by addition of antimicrobials, antioxidants and nutrients additives. Edible composite coatings were prepared from soy protein isolate (SPI), whey protein concentrate (WPC), carrageenan and alginate were used in the formulations as edible coatings. Pear pieces were coated and color, browning index (BI), firmness and sensory evaluation were measured at 4̊c in 15 days. Also the results show that pear pieces coated with whey protein-based coatings had higher L* and lower b*, a* and BI–value (BI-value for WPC and SPI coating are 21.93±0.3, 24.83±0.8 respectively) the result showed that shelf life and firmness of pears with edible coating being extended during storage. Between coatings whey protein concentrate (WPC) showed better results.