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

 Free radicals originate from oxidation reactions decrease food quality and also promote incidence of various diseases such as cancer. In this regard, the use of natural compounds with antioxidant properties, such as bioactive peptides, is of interest to many researchers. Food-derived bioactive peptides, can play an important role in the oxidative systems. Ultrasound, as a cheap and green technology, is widely used to extract proteins and antioxidant compounds. Ultrasound pretreatment before enzymatic hydrolysis can open the protein structure and increase the intensity of proteolysis by increasing the exposure of peptide bonds prone to enzymatic hydrolysis; which increases the production efficiency of bioactive peptides. Ultrasound treatment changes the three-dimensional structure of proteins. Therefore, a combination of pretreatment with ultrasound and sequential enzymatic hydrolysis can be a promising way to modify the function of proteins.

 In this research the effect of hydrolysis time and ultrasonic pretreatment on enzymatic hydrolysis of edible mushroom protein by pancreatic enzyme to produce peptides with high antioxidant capacity was evaluated. First edible mushroom was turned into powder and then, in order to optimize the production of hydrolyzed proteins with maximum antioxidant activity, the hydrolysis was performed 30, 60, 90, 120, 150, 180 and 210 minutes with a ratio of enzyme to substrate of 1% (based on the result of previous research) and at 40°C in four conditions (1- without ultrasound pre-treatment, 2- with ultrasound pre-treatment with 40% power, 3- with ultrasound pre-treatment with 70% power and 4- with ultrasound pre-treatment with 100% power) by ultrasound probe in 5 minutes before adding the enzyme. In the next step, the antioxidant capacity of hydrolyzed proteins was measured at different times by DPPH free radical scavenging activity, iron ion reduction power, iron ion chelation and total antioxidant capacity.

 The results showed that the highest DPPH free radical scavenging activity in untreated and treated samples with 40, 70 and 100% ultrasound power were 69.1, 77.45, 79.07 and 80.27, respectively. In most of the hydrolysis times, DPPH free radical scavenging activity in ultrasound treatment with 100% power was higher than the samples treated with 40 and 70% power. The highest total antioxidant capacity in untreated and treated samples with 40, 70 and 100% ultrasound power were 0.871, 1.025, 1.05 and 1.2 (absorption at 695 nm), respectively. In most of the hydrolysis times, the total antioxidant capacity in the samples treated with ultrasound with 100% power was higher than the samples treated with 40 and 70% power. The results showed that the highest reducing power of Fe3+ in untreated and treated samples with 40, 70 and 100% ultrasound power were 2.03, 2.40, 2.44 and 2.51(absorption at 700 nm), respectively. The highest iron ion chelation power in untreated and treated samples with 40, 70 and 100% ultrasound power were 25.22, 30.40, 26.52 and 41.10%, respectively. By increasing the ultrasound power in most of the hydrolysis times, the chelating power of iron ions in the ultrasound treatment with 100% power was higher than the samples pretreated with 40 and 70% power. The results showed that samples pretreated with 100% power ultrasound have the highest antioxidant properties compared to samples without pretreatment and pretreated with 40% and 70% ultrasound power. Based on the results, using ultrasound treatment with 100% power and during hydrolysis time of 60 minutes, a product with high antioxidant capacity was obtained and selected as a suitable treatment.

 The ultrasonic mechanism is attributed to its thermal effects, cavitation and mechanical efficiency, so that it can increase the mass transfer and increase the contact between the substrate and the enzyme or change the spatial structure of the substrate. The results showed that samples pretreated with ultrasound with 100% power have the highest antioxidant properties compared to samples without pretreatment and pretreated with 40 and 70% power. Therefore, the use of high-power ultrasonic pretreatment shortens the hydrolysis time to achieve peptides with higher antioxidant capacity and thus increases the efficiency of enzymatic hydrolysis.

In this research, the effect of ultrasound treatment at different powers and temperatures on the drying process of cornelian cherry by infrared dryer was investigated and modeled. The effect of the applied power by the ultrasonic device at three levels of 0, 75 and 150 W and the effect of the ultrasonic treatment temperature at three levels of 20, 40 and 60 °C on the mass transfer rate and the effective moisture diffusivity coefficient during the drying process of cornelian cherry were investigated. The results of this research showed that ultrasonic pretreatment before drying cornelian cherry by the infrared dryer, by creating microscopic channels on the product surface due to the cavitation phenomenon, makes it easier for moisture to exit from the product and thus reduces the drying time. By increasing the ultrasonic power from 0 to 150 W, the average drying time of cornelian cherry decreased from 73.2 minutes to 51.4 minutes. By increasing the treatment temperature from 20 to 60 °C, the average drying time of cornelian cherry decreased from 69.7 minutes to 55.7 minutes. The effect of power and time of ultrasound treatment on the effective moisture diffusivity coefficient changes of cornelian cherry was investigated and the results showed that with the increase in the power and temperature of the ultrasonic device, the values of this coefficient increase. By increasing the sonication power from 0 to 150 W, it was observed that the effective moisture diffusivity coefficient increased from 6.63×10-9 m2s-1 to 10.11×10-9 m2s-1. The average effective moisture diffusivity coefficient of cornelian cherry treated at temperatures of 20, 40 and 60 °C were 7.26×10-9 m2s-1, 8.10×10-9 m2s-1, and 9.45×10-9 m2s-1, respectively. In order to investigate the drying kinetics of cornelian cherry, mathematical models were fitted to the experimental data.

Evaluation of the effect of ohmic pretreatments and blanching (enzyme removal) on changes in the biochemical properties of carrots was the purpose of this research in the drying process using the response surface method. Sliced carrot samples were added and left at 3, 5, and 7 minutes and 40, 60, and 80 volts. In the blanching pre-treatment, carrot samples were subjected to hot air from boiling distilled water for 5, 10, and 15 minutes to complete the pre-treatment process. This study dried slices of carrot samples at 360, 600, and 900 W using a microwave dryer. After drying, the amounts of antioxidant, total phenol, and flavonoid contents were determined. Then the results were analyzed using response surface methodology. The findings revealed that the high voltage and time in the ohmic pretreatment, as well as the time in the blanching pretreatment, had the lowest decreasing antioxidant content during the drying process. The lowest concentration of antioxidants was at the lowest voltage and time. Increasing the microwave power reduced the content of antioxidants, and lower drying powers had a higher antioxidant content in the dried samples. For the total phenol and flavonoid content in the ohmic pretreatment, the time and voltage of the pretreatment decreased their content, and increased power caused more total phenol and flavonoid content to be retained in the samples. Also, based on the optimization performed, the best microwave power was 360, 40 V ohmic voltage, and 3 minutes.

In this research, carrots were first cut into equal pieces and then subjected to different treatments at different levels. The voltage levels were at 40, 60 and 80 volt in ohmic pretreatment and at 3, 5, and 7 minutes. The parameters studied in the blanching pretreatment included time, with different levels of 5, 10, and 15 minutes. Immediately after pretreatment, samples were dried in microwaves at 360, 600 and 900 watts. Finally, for each case of microwave dried and pretreated samples and their different levels, the energy efficiency values and their lost energy were calculated. According to the results, in the majority of cases, we see that increasing the amount of microwave power increases the energy efficiency, and subsequently, the lost energy decreases, so that the maximum value was 15.8797%. In the study of the effect of voltage in the ohmic pretreatment, a similar result was obtained, with the highest energy efficiency of 15.7061%. Also, in evaluating the effect of time parameter in ohmic pretreatments, it was observed that with increasing pretreatment time, the amount of energy efficiency was also increased and the energy lost was reduced, so that the highest amount of energy efficiency and the lowest amount of energy lost were respectively 15.7409% and 8.2358 MJ were measured.

Dried and powdered onionshave many applications in food production.But during onion drying, nonenzymatic browning reaction happens which decreases its quality. In this study, different pretreatments before onion drying were used to prevent destructive reactions. After pealing and grating the onions, they were treated with three treatment methods of sodium metabisulphite 0.5%, citric acid with pH=4 and 10% salt (NaCl) for two minutes. Then, the treated onions were dried at cabinet dryer at two temperatures of 800C and 900C till reaching moisture content of 6 and the produced powders were kept for two months at room temperature and qualitative tests were carried out on them at days 1,30 and 60. Results showed that the pretreatments had significant effects(p

The purpose of this research was to study the effect of thin layer drying conditions (temperature at three levels of 60,70, and 80 oC, air velocity at two levels of 1/5 and 2/5 m/s, and four pretreatments including potassium carbonate and Paksan drying oil, olive oil, hot water without pretreatment (control)) on cabinet drying process of grape and color of obtained raisin. Six mathematical models were fitted on drying data and the best one was selected according to coefficient of determination (R2), Root Mean Square Error (RMSE) and coefficient of relative average deviation (P). The results showed that temperature, air velocity and pretreatment have significant effects on drying rate and color of raisin. Among these models, two term and page models showed more ability to evaluating and describing drying behavior of grape. Diffusion coefficient values were between 4/6274×10-10 to 8/6541×10-10 m/s2 and activation energy obtained 13470/83 J/mol. The best values of lightness and redness were related to dried raisin at 60 oC and the maximum value of yellowness was related to dried raisin at 70o C. Drying air velocity just significantly affected the redness. Increasing drying air velocity decreased the redness. It was also found out that potassium carbonate and Paksan drying oil pretreatment caused the best raisin color.

This research work was studied to evaluate the effects of different pretreatments of blanching and microwave drying on the qualities and appearance properties of slice quince. In this experiment, three blanching treatments including hot water (Wt), water vapour (Vt), citric acid (At) and three blanching time (2, 4 and 6 min) and also a control treatment were considered with three replications. The results showed that the color differences decreased when the samples pretreated in compare of control sample. Minimum shrinkage was observed in pretreated samples in compare of control. Among the pretreated samples, minimum shrinkage were belong to samples which pretreated by citric acid and vapour. It was occurred in the blanching times of 4 and 6 min. Maximum and minimum vitamin C was observed in vapour and hot water pretreated samples, respectively. Therefore, blanching by vapour up to 4 min and hot water up to 2 min found as the optimum conditions for reaching the best quality of quince fruit in microwave drying process.

In order to investigate the effect of different levels of temperature، velocity and pretreatment on the drying time of thin layer of Barberries (berberis vulgaris)، an experiment using a factorial experiment conducted carried out based on completely randomized block design with three levels of temperature and three levels of velocity for untreated berries and treated berries with heat shocking and «6% k2co3 + 3% olive oil» emulsion with three replicates. Drying times were affected by temperature and pretreatment at the probability level of 99%. The maximum drying time was recorded 2920 minutes for untreated berries at the temperature and velocity of 60 ºC and 0. 3 m/s respectively and the minimum drying time was recorded 70 minutes for treated berries with k2co3 and olive oil emulsion. In our study multi layer perceptron (mlp) Neural Network with an adjustment learning algorithm of Levenberg-Marquardt with sigmoid logarithm and sigmoid tangent functions were used. The best topology of MLP with LM learning algorithm and Tansig threshold function can predict the moisture content was 4-30-16-1 with correlation coefficient of 0. 9992 and actual error of 0. 00025. Besides the best topology of this neural structure with Logsig threshold function can predict the moisture content was 4-25-5-1 with correlation coefficient of 0. 9991 and actual error of 0. 00032. These results indicate ability of artificial neural network to model and predict drying process.

Aim of pre-treatment drying of mulberry was to reduce the moisture content to a level that allows safe storage over an extended period. In this research after physical and chemical pretreatments، mulberry was dried industrially (cabin dryer). Non Enzymatic Browning was tested at 440 nm by spectroscopic method. Organoleptic tests were done by trained panelists. Hardness and cohesiveness of dried mulberries were measured by a texture analyzer. Statistical method was completely randomized design with 10 treatments and three replicates. The results showed that least intensity of brown color was in pretreatment of fruits with potassium meta bisulfate 0. 5% +calcium chloride %1. The highest water absorbance was in ethyl oleate 2%. Panel tests showed highest score for overall acceptance in pretreatment of fruits with ethyl oleate 2% +potassium meta bisulfate 0. 5%، highest score for texture with ethyl oleate 2% +calcium chloride %1، highest score for color with ethyl oleate 2% +potassium meta bisulfate 0. 5%، highest score for odor with ethyl oleate 2% +citric acid %1 and also ethyl oleate 2% +ascorbic acid1% and highest score for taste with ethyl oleate 2% +calcium chloride %1. Totally it is concluded that ethyl oleate 2%، ethyl oleate 2% +citric acid %1، oleate 2% +ascorbic acid1%، ethyl oleate 2% +potassium meta bisulfate 0. 5% and oleate 2% +calcium chloride %1 are the best pretreatment for drying of white mulberry.