Azam Ayoubi; Nasser Sedaghat; Mahdi Kashani-Nejad; Mohebbat Mohebbi; Mehdi Nasiri mahalati
Abstract
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 ...
Read More
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.
Azam Ayoubi; Nasser Sedaghat; Mahdi Kashani-Nejad; Mohebbat Mohebbi; Mehdi Nasiri mahalati
Abstract
Introduction: 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. ...
Read More
Introduction: 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 methods: 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 and discussion: 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.
Mahboubeh Sarabi; Fakhri Shahidi; Ahmad Reza Bahrami; Seyed Ali Mortazavi; Mohammadreza Nassiry; Massoumeh Mehraban Sangatash; Marzieh Hosseininejad
Abstract
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 ...
Read More
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.
Parnian Pezeshki; Abdolmajid Maskooki; Mohammad Elahi; Seyed Ali Mortazavi
Abstract
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 ...
Read More
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.
Elmira Haghighi; Massoumeh Mehraban Sangatash; Seyed Ali Mortazavi; Mahboubeh Sarabi; Reyhaneh Noorbakhsh; Mohammad Armin
Abstract
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 ...
Read More
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.
Mohsen Esmaiili; Ali Hassanzadeh
Abstract
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 ...
Read More
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.
