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

Raisin is one of the most nutritious dried fruits and rich in various vitamins, minerals, fiber and antioxidant compounds (Mehraban et al. 2015). Iran is one of the major producers and exporters of raisin in the world. During storage period, raisin turns hard and sticky due to exudates syrup and moisture loss. It has been shown that application of edible coating could be useful to overcome this problem and extend shelf life of this product (Ghasemzadeh et al. 2008). Waxes and vegetable oils have been used to coat raisin (Debiofort et al. 1998) Ayoubi et al (2015) coated raisin with carnuba wax and glycerol monostearate. Also, Ghasemzadeh et al (2008) used edible coating based on starch and pectin to coat raisin. Sodium alginate is a water-soluble linear polysaccharide derived from alginic acid and has been considered as an edible coating due to its low cost, non-toxicity and biodegradability (Danapal and Associates 2012). In the present study, the effect of edible coating based on sodium alginate to maintain the keeping quality of raisins during storage at 25 °C for 6 months has been investigated.

raisin was produced from Seedless Asgari grape variety with the soda oil method. It was coated with sodium alginate at levels of 1 and 2%. After coating, samples were packaged in Zip-kip polyethylene bags and stored at 25 °C for 180 days. Physicochemical (weight loss, brix, pH, total phenol, color and hardness), microbial (total count) and sensory (color, texture, taste and overall acceptability) properties were determined during storage in the first day and 45, 90, 135 and 180 days after starting the storage. The weight loss was calculated from the difference between raisin weight in 45, 90, 135 and 180 days with the initial weight. Brix was measured by a refractometer (Protable VBR model, Switzerland). The pH value was measured by a digital pH meter (3020, Jenway, UK). In order to determine the total phenolic contents, the Folin–Ciocalteu method (Taga et al. 1984) was employed and measurements were done at 765 nm with a spectrophotometer (UNICO 2802, China). The color measurement was done using a colorimeter (TES-135A, Taiwan). Hardness of raisins was determined in a puncture test using a QTS texture analyzer (CNS Farnelll, Essex, UK) equipped with a needle probe (stainless steel cylinder of 2 mm in diameter with a conical needle bit) and a test speed of 60 mm/ min during the test. Hardness was defined as the maximum force to puncture raisin from the top to a 2mm depth (Rolle et al. 2011). To determine the total count, pour-plating method was used in PCA medium and incubation was performed at 37 °C. The sensory evaluation was performed by 5-point hedonic scale (1 most disliked, 5 most liked) by 10 trained panelists. The sensory evaluation of all treatments was carried out during storage time (in the first day and 45, 90, 135 and 180 days after storing). A factorial test in completely randomized design with 3 replications was utilized in this study. Analysis of variance (ANOVA) was performed by using MSTAT-C software. Duncan's multiple range test was used to compare the means at the 5% significance level and the graphs were plotted by Microsoft Excel software.

The results of analysis of variance showed edible coating significantly affected the weight loss. Sodium alginate coating reduced the raisin weight loss. In addition, storage had significant effect on weight loss. The weight loss was gradually increased during the storage period. The results of analysis of variance indicated significant effect of edible coating and storage time on raisin brix. During the storage time, brix increased, while the rate of this increasing in samples coated with sodium alginate was less than the control. The results also showed the effect of edible coating and storage time on the pH of raisins was not significant. During storage, the total phenolic content of raisins was gradually reduced. The edible coating reduced the intensity of this reduction. At the end of the storage period, the most total phenol content was observed in 2% sodium alginate treatment. The results of the color parameters evaluation showed that during the storage time lightness of raisin decreased. In addition, the effect of edible coating on this color parameter was significant (p<0.01). L of 1% sodium alginate treatment was significantly more than the control at 180 days after storing and this significant difference observed in 2% sodium alginate treatment at 45, 90 and180 days after storing. The effect of edible coating was not significant on redness but this color property significantly increased during storage period. It seems that browning reactions caused this color change. Also evaluation of yellowness results indicated sodium alginate coating had not significant effect on this color parameter. Storage caused significant changes in raisin yellowness (p<0.01). During storage time initially b value increased and then decreased. The most lightness and the lowest value of redness to yellowness ratio represent the best color of raisin. Analysis of variance show redness to yellowness ratio of raisin significantly increased during storage time (p<0.01). The edible coating was significantly effective in reducing rate of this change. After 180 days storage, the highest and lowest a/b value were related to the control (1.07) and 2% sodium alginate treatment (0.69), respectively. Observations showed raisin texture gradually hardened during the storage period (p<0.01). According to the results of study, the edible coating has not significant effect on raisin hardness. The data showed edible coating had no significant effect on total count, but microbial growth significantly decreased during storage (p<0.01). Acidity, water activity, inhibitor compounds such as phenolic compounds and some products of non-enzymatic browning reaction of Millard are some factors that inhibit microbial growth in raisins during storage (Zhao and Hall 2008; Bower et al. 2003). Based on the sensory evaluation results, storage darkened raisin color and reduced the color score. Edible coating was effective in preserving the color so that at the end of storage time the color score of coated samples was significantly more than the control. During storage time taste and texture scores significantly decreased. Although the edible coating had not significant effect on these sensory properties. Storing significantly reduced the overall acceptance score of raisin. At the end of the storage period, the overall acceptance score of coated samples were more than the control; However, according to the results of Duncan's multiple range tests only the difference between the overall acceptance score of the control and 2% sodium alginate treatment was significant at 135 days of storage.

The present study investigated the effect of lipid coatings and atmosphere of packaging on instrumental and sensory properties (texture and color) of raisin. Raisins were coated with carnauba- wax (0.5% w/w) and stearic monoglyceride (0.5% w/w) and raisins packaged under two different atmospheric conditions: normal and vacuum. The changes occurred in the moisture content, texture, color parameter (L*, a*, b* and ΔE* values) and sensory attributes of raisin were determined during 12 weeks of storage at 20°C, 35°C and 50°C. Instrumental and sensory attributes were correlated with Pearson Correlation Coefficient. In all samples, the hardness value increased along with storage time, while the moisture content decreased. But presence of lipid coating on rainsin significantly (P

The purpose of this research was study effect of 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 oil, olive oil, hot water and no pretreatment (control)) on drying grape process and quality of raisin including rehydration, shrinkage, hardness and browning index. The results showed that temperature, air velocity and pretreatment have significant effects on drying rate and quality of raisin. Drying rate increased with increasing temperature and air velocity and with application of preatreatment. The best values of hardness (0.73 N), shrinkage (81/04%) and the least value of browning index (0/157) were related to dried raisin at 60 oC and most value of rehydration (1/266) was related to dried raisin at 70 oC. Air velocity just significantly affected on browning index. Increasing air velocity decreased browning index. Also between used preatreatments , potassium carbonate and paksan oil caused best physicochemical results.

Raisin is a principal traditional export product of Iran and has a special position in the foreign trade of the country.During storage, the product turns sticky and hard due to exudates syrup and moisture loss. To solve this problem, the application of edible coating would be an appropriatesolution. Edible coating may enhance the boundary layer resistance resulting to the enhanced shelf life of the product. Edible coatings are thin layers of edible materials applied to the product surface in addition to or as a replacement for natural protective waxy coatings and provide a barrier to oxygen, water and solute movement. They are also applied in foods to minimize the migration of components within the food systems or between the foods and their surrounding environment. They are used directly on the food surface by spraying, dipping or brushing to create a modified atmosphere. There are different kinds of films which are used such as polysaccharide, protein, lipid and composites. Lipid based coatings are primarily used for their hydrophobic properties which make them good barriers to water loss. In addition to preventing water loss, lipid coatings have been used to improve appearance by generating a shiny coverin fruits and vegetables, and to decrease respiration, thereby extending shelf life. The moisture barrier properties of hydrophilic coatings can sometimes be improved by addition of lipid materials The purpose of this research was to study the effect of lipid based edible coating (glycerylmonoestearate and carnauba wax) on physicochemical and microbial properties of raisin.
Material and Raisin samples (cvAskari)were dried usingsoda oil method and treated with coating materials based on lipid with essential oil of thyme (thymus vulgaris).Glycerylmonoestearate, carnauba wax and tween 80 were purchased from Sciencelab, Sigma-Aldrich and Merck Co. respectively.
Raisinswerecoated with the following coating solutions: -Aqueous solution of tween 80 (0.5% w/w)
-Aqueous solution of glycerylmonoestearate (0.5% w/w), tween 80 (0.5% w/w)
-Aqueous solution of glycerylmonoestearate (0.5% w/w), tween 80 (0.5% w/w), 150 ppm essential oil of thyme
-Aqueous solution of carnauba wax (0.5% w/w), tween 80 (0.5% w/w)
-Aqueous solution of carnauba wax (0.5% w/w), tween 80 (0.5% w/w), 150 ppm essential oil of thyme
Control sample was treated with aqueous solution of tween 80 (0.5% w/w).Distilled water was used for preparing all of coating solutions. Coating solutions were stirred and heated to 75oC (melting point of coating materials) for 30 min on a hotplate with a magnetic stirred to obtain uniform solutions. Dipping technique was used for coating of raisins. The coated raisins were placed on a basket to drip off residual coating solution and were dried in 25oC. The raisin smples were packaged in a 3 laminatedlayer bags (PE/PA/PE) with thickness of 80µ by Henkelman packaging machine and were stored at20, 35 and 50oC for 12 weeks. During the storage period, moisture content, water activity, hardness, color parameters (L*(lightness), a*(redness) and b*(yellowness)), percent of pestilence and microbial properties (total count, mold and yeast) were evaluated. Hardness of raisins was determined in apuncture test using a QTS texture analyzer (CNS Farnelll, Essex, UK) equipped with a needle probe (stainless steel cylinder of 2 mm of diameter with a conical needle bit) and a test speed of 60 mm. min−1 during the test. Hardness was defined as maximum force to puncture raisin from the top to a 2mm depth (Rolleet al. 2011).For colormeasurement, raisins were placed in to a black wooden box (interior size of 0.5 (width) × 0.5 (length) × 0.8 (height) m3 and were illuminated using 3 fluorescent tube lights (10W, 6500K; 40cm in length). A digital camera (Canoon EOS 1000D, Powershot, Taiwan) was located vertically at a distance of 20cm from the raisin surface. The images were preprocessed by Adobe Photoshop software, version 5.5. The Color properties were analyzed using ImageJ software, version 1.44o. The experiments were factorial with a completely randomized design. The coating material, temperature and storage time were the independent variables. Analysis of variance (ANOVA) was conducted for data using MSTAT-C software, version 1.42 (Michigan State University). Differences among the mean values were also determined using Duncan’s Multiple Range test. A significant level was defined as a probability of 0.05. The experiments were carried out on 4, 8 and 12 weeks after storage with three replications.
Results showed that coating, temperature and storage time would have considerable effect on the physicochemical and microbial properties of raisin. Coating caused decreasein moisture loss, hardness, lightness and redness. Increasing temperature and storage time increasedmoisture loss and hardness. Minimum hardness values were measured for 20 oC and 4 weeks storage and maximum hardness values were related to 50 oC and 12 weeks storage. Also it seems that increasing temperature and storage time influences thehardness by increasing moisture loss. Increasing temperature and storage time significantly decreased L* (p≤0.01). Increased enzymatic browning in raisins with increasing temperature was accompanied by an increase in a* value, and a decrease in b* value and caused to presenting dull colors. Total count, mold and yeast of coated samples decreased during storage period. Carnauba wax was more effective than glycerylmonoestearate on stability of raisin. Essential oil of thyme also caused improving color and microbial properties. Least values of redness (-2), total count (2.06 log cfu/g) and mold and yeast (1.32 log cfu/g) were related to carnauba wax coating with essential oil of thyme.

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.

Raisins are dried grapes that may be eaten raw or used in cooking, baking and brewing as an ingredient. Iran is one of the major exporters of raisins in recent years and Iranian raisins are exported to many countries. It is important to ensure of microbiological quality and safety of raisins. The aim of this study was isolation and identification of mycoflora from main raisin’s varieties (Poloie, Pikami & Teiphi) produced in Khorasan Razavi Province. Four types of culture medium (Yeast Extract Glucose Chloramphenicol Agar (YGC), Potato Dextrose Agar (PDA), Czapek Dox Agar (CA) and Dichloran Glycerol Agar (DG18)) were used for isolation. The highest contamination was found in Teiphi raisin samples. The drying method was not effect on fungi contamination. For Fungi Identification, Macroscopic and Microscopic features were investigated. The Result showed that frequently isolated fungi were Aspergillus and Penicillium species. The fragment (600 bp) of Internal Transcribed Spacer 5.8SrRNA of isolated colonies was amplified using polymerase chain reaction for identification down to the species level. According to the results, the raisins had varius species of Aspergillus, Penicillium, Rhizomucor, Mucor, Alternaria and Cladosporium. Aspergillus niger was the most abundant fungi.

Toxicogenic potential of Aspergillus tubingensis isolates occurring on grape and raisin in southern regions of East Azerbaijan province were evaluated using of ammonia vapor, UV photography and high performance liquid chromatography (HPLC) methods. For this purpose, fungal isolates were grown on Capek Yeast Autolysate Agar (CYA) and Coconut Cream Agar (CCA) media and Ochratoxin A (OTA) production was evaluated. The results of this study showed that toxin production was detectable on 69%, 41% and 65% of the isolates using ammonia vapor, UV photography and HPLC methods, respectively. The compatibility of ammonia vapor vs. HPLC, HPLC vs. UV, ammonia vapor vs. UV and three mentioned methods was 50%, 69%, 62% and 42%, respectively. According to the results of this study, UV photography method appeared to be more efficient for detection of toxigenic isolates of A. tubingensis in comparison to ammonia vapor. The amount of OTA produced by isolates was determined 29-1089 μg/kg using HPLC.

Raisin is a principal traditional export product of Iran and has occupied a special position in the foreign trade of the country. During storage period, the product turns sticky and hard due to exudates syrup and moisture loss. To overcome this problem the application of edible coating suggests being of proper assistance. Edible coating may enhance the boundary layer resistance resulting enhanced shelf life of product. In this research the method of Accelerated Shelf Life Testing (ASLT) used for evaluation of storage and sensory properties (texture, colorو taste and overall acceptability) of raisin. Raisin was treated with coating materials based on lipid (glyceryl monoestearate and carnauba wax) with 150 ppm essential oil of thyme (thymus vulgaris) and stored at 20, 35 and 50oC for 12 weeks. During this period of storage sensory properties were evaluated and estimate the modeling shelf life of raisin. Results showed that coating, affect on texture and color significantly and caused increasing shelf life of raisin. Temperature and storage time also showed significant effects on total sensory attributes. Maximum shelf life (394 days) determined at 20 oC for carnauba wax coating with essential oil of thyme based on overall acceptability and linear regression and second order function had best fit with R2≥0. 94 for all of treatments.

Baker's yeast is one of the most important additives for improving the bread quality and molasses is a commonly used source of sugars for producing baker's yeast. Nowadays, due to increasing the fermentation industries and limitation in suitable sources of sugars, the use of other carbohydrate sources may be considered.In this study, the possibility of baker's yeast production in three cultures of date, raisin, enzymatic hydrolyzed whey and molasses as a control was investigated.Also, the total amount of biomass, consumption of sugar, strength of levy and kinetic's parameters of growth in all mediums were determined.For enriching the mediums, yeast extract and pepton were used in order of 3.5 and 7%, respectively. Fermentation process carried out during 12 houres and the temperature is maintained constant to 30 C°. Agitation was of 150 turns per minutes and ventilation fixed at 2 V.V.M. According to the results,maximum and minimum amount of biomass were 93.33 and 81.35 g/l that they related to date and whey, respectively.The consumption of sugar except whey which had the lowest level, in other cultures had no significant difference.The highest yield (0.35g/g) is observed in date but the lowest yield was 0.32 g/g in whey. Also, the baker's yeast which growed in raisin extract, had the highest value in strength of levy.

Drying foodstuffs can have negative effects on quantitative and qualitative characteristics of the products, including porosity and bulk density. Therefore,novel technologies can be used to improve these characteristics. In this study, apparent density changes during drying grapes pretreated with ultrasound for 10, 20 and 30 minutes, and carboxymethyl cellulose (CMC) at three concentrations of 0.1, 0.2 and 0.3 percent was evaluated. In order to dry the grapes, a tunnel dryer was used and the samples apparent density was calculated during drying. The results showed that apparent density of the grape samples is increased with increasing ultrasound time and decreasing CMC concentration. Furthermore, apparent density was modeled through existing models in the literature as well as the models proposed in this study. One of the proposed models (Model 6, Table 2) was selected as the most appropriate model to predict changes in the apparent density of the grapes during drying.

The aim of this study was to investigate the mold contamination of main raisins varieties produced in Khorasan Razavi Province with aflatoxin-producing fungi and determine amount of aflatoxins. For this purpose 50 samples were collected from different markets in Kashmar, Khalil abad, Bardaskan, Mashhad and Quchan (10 samples from each city). The result showed that from 50 raisin samples, 44 samples (88%) were contaminated with fungi. The lowest and highest level of fungal contamination were observed in Quchan and Kashmar, respectively. Aflatoxigenic potential of fungi that isolated from contaminated samples were evaluated using Coconut Agar Medium and under UV light (365 nm). It is observed that 29 samples (65.9%) had Aflatoxigenic fungi. The presence of aflatoxin was confirmed by high pressure liquid chromatography. No sample had greater AFB1 levels than the maximum allowed levels (5 ng/g) in raisins accepted by ISIRI (Institute of Standards and Industrial Research of Iran). Although the amount of AFB1 in raisin varieties produced in Khorasan Razavi Province, does not appear to create a serious public health problem at present, because of Percapita consumption of raisins in Iran (22 kg/year) it is necessary to consider it as a serious health problem.

The sorption isotherm and state diagram of sundried, golden and sultana raisins were constructed for investigation and comparison of the product stability. The isotherms were measured at 15, 25 and 35 °C using an isopiestic method and the data were modeled with GAB model. Glass transition temperatures of the products were measured by differential scanning calorimetery (DSC) and fitted to Gordon Taylor model. Moisture sorption results indicated that the amount of moisture adsorption and the GAB monolayer moisture contents were the highest in sultana and the lowest in sundried raisins, at all of investigated temperature levels. Critical water activity (CWA) and critical water content (CWC) were estimated from the state diagram and the relationship between water activity, the glass transition and the equilibrium moisture content. According to the state diagram specification, CWC (dry basis) and CWA of raisins were estimated lower than 0.03 and 0.05, respectively.

Achieving optimum drying conditions can affect the processing time and improvement of raisin quality. Temperature, air velocity and pretreatment are important factors in grape drying process and its quality. In this research, effect of the following conditions on quality of Black currant raisin was studied: air temperature at four levels of 50, 60, 70, and 80 ºC, air velocity at three levels of 1, 2 and 3 m/s, and four pretreatments including hot water, %5 potassium carbonate, %0.4 olive oil, %0.5 sodium hydroxide (caustic soda) and control without any pretreatment. The results showed that some factors such as air temperature, air velocity and pretreatment have qualitatively significant effects on browning index, rehydration ratio, and shrinkage. Similarly temperature and pretreatment factors have a significant effect on acidity. Raisins dried at 70ºC and pretreated in hot water, %5 potassium carbonate, %0.4 olive oil and %0.5 sodium hydroxide have better quality.

Now adays around the world، raisin concentrate is considered as a valuable material for producing nectars، raisin paste، raisin juice and confectionary industries as well as a natural alternative for sugar، there are numerous raisin production which condensed concentrate is of great importance It has variable properties and industrial utilizations. In order to extract it، tests were conducted in three levels of extraction temperatures (40°C، 60°C، 80°C)، These levels of solvent propertion (1:1، 2:1 and 3:1) and three levels of condensation temperature. (65°C، 75°C، 85°C). At the end the chemo- physical characteristics (color، viscosity، freed sugar concentrate weight and production efficiency) were studied carefully، then microbial tasts (mould، fermentation and total counting) were carried on. After the statistical analysis، those extracted at the extraction temperature 80centigrade degrees and 75 centigrade degrees condensation temperature، and solvent proportion 2:1، 3:1 leading to better result are suggested، considering higher extracted. as well as condensation in thermul conditions.

Moisture desorption isotherms are useful in food dehydration، storage and packaging. Due to the complex food composition، theoretical prediction of the isotherms is not possible and experimental measurements are necessary. Moisture desorption isotherms of Thompson seedless raisins were determined at 30، 40، 50، 60، 70 and 80 ºC، using the standard static gravimetric method developed by the European cooperation project COST 90. GAB، Smith، Oswin، Halsey، Henderson and D’Arcy- Watt equation were fit the data. The experimental data were fitted well with Halsey equation at 30 ºC and 40 to 80 ºC، with D’Arcy-Watt equation. So، Isosteric heat of desorption data obtained at different moisture content.