JOURNAL OF FOOD RESEARCH (UNIVERSITY OF TABRIZ)
Year:2010 | Volume:3/20 | Issue:1|Papers Count:12

Probitics are dietary supplement of live microorganisms which confer a health benefit on the host when administrated in an adequate amount in the gastrointestinal system. Lactic acid bacteria (LAB) are the most common type of microbes used as probiotics. Following significant developments in the dairy industry and an explosion in interest in the use of probiotics as functional foods, probiotic dairy products look at advancements in the dairy industry. Traditional yogurts and cheeses have long been considered an ideal vehicle for delivering probiotic bacteria to the human gastroinstestinal tract which explains the widespread use of probiotic cultures in dairy products. Two regions, Heris and Sarab, have traditional dairy products that may be source of many LAB.The aim of this study was to identify and isolate potentially probiotic bacteria from traditional cheese and yoghourt of Heris and Sarab regions. To achieve this goal, LAB were isolated and characterized using phenotypic methods (Gram staining, physiological and biochemical tests). Then their acid and bile tolerance, as the primary probiotic characteria, were investigated. 16s rRNA gene of lactobacilli and Enterococci was amplified for identification of bacterial strains. Genotyping of isolates was performed by RAPD-PCR analysis using four randomly primers.At the end of the study, 15 lactobacillus spp. and 16 Enterococcus spp. were isolated from traditional dairy products of these regions that could be potentially used in the industrial dairy products.

Nowadays, oil extracted by cold press is getting more demand in the market. Important issues in the application of this method are the low oil extraction yield, and the low amount of minor compounds (phytosterols, tocopherols) present in the extracted oil compared with the extracted oil by the solvents. Many efforts have been made to improve the extraction efficiency of the cold press. The aim of this study was to evaluate the effect of microwave treatment on the extracted oil quality from rapeseed. Rapeseeds were treated with microwave (2450 MHz) in three different times (0, 2 and 4 min) and their oils were then extracted by press. The oil samples were then evaluated for physical and chemical properties, and fatty acids composition. There was a significant difference (p<0.05) among samples on the oil extraction yield, chlorophyll content, oxidative stability. It was found that microwave treatment had no significant effect (p<0.05) on the refractive index and the fatty acids profile of the extracted oil samples. The oil extracted from the treated rapeseed samples had significant differences (p<0.05) in the acid value. The oil extracted by using the solvent and microwave for 4 min had the highest and lowest peroxide values, respectively. Microwave treatment of rapeseeds for 4 min increased the oil extraction yield (by 10%), chlorophyll content (by 5.3%), oxidative stability (7h), and reduced the acid and peroxide values. According to the obtained results, it can be concluded that microwave treatment of rapeseeds before oil extraction by the cold press can improve oil extraction yield and quality and enhance its minor compounds level.

Frying is a popular way for food cooking. Selection of a suitable oil is an important factor that affects the quality of the fried foods. This research was conducted in order to optimize the blend of palm olein and colza oils as frying oil. Firstly, various compositions of these oils were prepared and their heat resistance was evaluated at 120°C using rancimat method. The oil blends were used for the frying of potato in order to evaluate their frying performance. Frying was done for 5 successive days at 180°C and changes in total polar compounds (TPC), acidity and peroxide values of oils were determined. The results showed that TPC, acidity and peroxide value increased during frying. The increase of colza in the composition of oil blend increased the peroxide value. From the results of this study, a blend of palm olein and colza oils with a ratio of 9:1 was chosen as the best formulation. This formula had the highest induction time (18.72h) in rancimat method and its TPC (17.72%) was the lowest after frying.

To study the effects of calcium chloride on the quality and shelf life of tomato, an experiment was conducted in the Agricultural and Natural Resources Research Center of the West Azarbijan during two years (2004-2005). After the growth and fruit set, calcium chloride at 0 (control), 0.5% and 1% concentration was sprayed on three cultivars of tomato at three times. Tomato fruit was harvested in the firm red condition and stored at 5 and 20±2oC (room temperature). The results showed that calcium chloride had a significant effect on TSS, pH, decay percent and shelf life. Titrable acidity (TA) and loss of weight was not affected by calcium chloride. The highest TSS was obtained at 0.5% calcium chloride. On the other hand, the highest pH and shelf life and the lowest decay percent were found at 1% calcium chloride. Roygrand cv. had the lowest TSS in control samples but the highest TSS at 0.5% calcium chloride at 5oC. pH and TA in Koral cv. with 0.5% calcium chloride were higher than the other treatments. In all the cultivars, an increase in the calcium chloride concentration decreased the decay percent and increased the shelf life. Storage temperature affected all the traits except the pH. The fruits stored at 5oC had a higher TSS, TA, shelf life and a lower weight loss and decay in comparison with the stored tomatos at room temperature.

Undesirable changes including the exchange of carbon dioxide and humidity through the shell-pores and cracks, take place immediately following the lying of egg.  One of the main strategies to control these defects is coating the egg-shell by oil and polymer materials. In the present study, the effect of chitosan (2%) and zein (10%) biopolymers alone and in combination with oregano-essential oil (EO) on internal changes such as percentage of weight loss, pH, Haugh unit, Yolk index and egg quality, as well as sensory factors including surface smoothness, odor, surface glossiness and overall acceptability of the eggs stored for 5 weeks at 25oC, were investigated. The results showed significant differences between all treatments and controls (P<0.05). Incorporation of EO to the chitosan and zein coating solutions had not significant effects on internal factors of all treatments during the storage period (P>0.05). In the sensory evaluation of eggs coated with chitosan and EO, the results showed significant differences with chitosan solution alone whereas, such differences could not be observed for zein and zein plus EO samples. Therefore, coating with both the biopolymers had considerable impact on the internal quality of eggs. In addition, the coating extended the shelf-life of eggs to 2-4 times at the room temperature. Moreover, when EO added to the coating solution, enhanced consumer acceptability of all the coated eggs was observed.

This research was done in order to determine the copper, zinc and iron levels in three fish muscles, namely Mullet (Mugil auaratus), Sefid (Rutilus frisii kutum) and Commom carp (Cyprinus carpio), from four fishing sites (Chaloos, Anzali, Roodsar and Fereidon kenar) of The Caspian Sea. The concentration of metals was measured by atomic absorption spectrophotometry (AAS) on the basis of mg/kg dry weight of muscles. The mean concentration values of copper in muscle of Mullet, Sefid and Common carp were 3.14±1.17, 3.69±2.24 and 3.39±1.24, respectively. The mean Concentration values of zinc in the same species were 43.46±14.01, 37.99±15.00 and 73.81±21.14, respectively. Also, the mean concentration values of iron were 81.11±17.99, 73.59±16.59 and 94.78±20.13, respectively. Concentrations of zinc and iron were significantly affected by the fishing sites and fish species (P<0.05). The highest concentrations of zinc and iron were in Common carp which were recorded from Anzaly and Chaloos fishing sites respectively (P<0.05). Trace elements in muscles of the investigated fishes were in the permissible safety levels for human consumption. 

Effect of three different hydrocolloids, pectin, guar and carrageenan in a concentration of 1, 2 and 3% (w/w flour basis) and also their combination in concentration of 2 and 3% (w/w flour basis) on sensory characteristics and shelf life of gluten-free breads was evaluated. The results showed that all hydrocolloids used in a concentration 1% produced gluten-free breads with acceptable sensory characteristics in the first day of evaluation, compared to those of control bread (made from wheat flour). In the second day of evaluation, a relatively sensible reduction in the sensory scores of glutenfree breads produced from all hydrocolloids was observed. Nevertheless, the sensory scores of all treatments except pectin 3% and wheat starch control were in an acceptable range. However, storage for the third day caused a significant (a<0.05) reduction in the sensory scores of gluten-free breads compared to those of fresh samples, except for guar 2 and 3%, carrageenan 2%, guar-pectin 2 and 3%, guar-carrageenan 3% and pectin-carrageenan 3% treatments. Gluten-free breads produced from a combination of hydrocolloids such as guar-pectin, guar-carrageenan and pectin-carrageenan in both 2 and 3% concentrations received the highest sensory scores and remained more fresh, compared to those produced from single hydrocolloids. In general, gluten-free breads containing hydrocolloids remained less fresh compared to control breads. Among hydrocolloids evaluated in this study, guar-pectin 2 and 3% produced gluten-free breads with desired sensory characteristics and staling scores. Whereas, breads made from starch, pectin 1% and carrageenan 3% showed a rapid staling.

The effect of the probiotic strains of Lactobacillus casei (ATCC 39392 Collection, Australia) as adjunct culture on proteolytic and lipolitic patterns of Iranian white cheese produced by ultrafiltration technique was investigated. Four treatments of UF Iranian white cheese were produced: control I (C1), with a commercial starter culture mix including Lactoccocus lactis subsp. cremoris, Lactococcus lactis spp diacetylatis), control II (C2), with commercial starter culture mix and the probiotic L. casei, LC with a commercial starter culture mix and probiotic L. casei (uncapsulated) and LCC with commercial starter culture mix and probiotic L. casei capsulated with Sodium Alginate by extrusion method. The cheese samples were ripened at 8-12 oC for 60 days. Assessment of proteolysis and lipolysis in the probiotic cheeses were investigated by determination of soluble nitrogen (SN) at pH 4.6 (SN-pH 4.6), tricholoracetic acid soluble nitrogen (TCA-SN), Free aromatic amino acids of Tyrosine-Trypotophan and Urea-polyacrylamide gel electrophoresis and free fatty acids (FFA) receptively. The results showed that amount of SN-pH 4.6, SN-TCA, Free Tyrosine-Trypotophan and FFA in all cheeses increased progressively during ripping, but the increase was more intense after 45 days of the initial ripening period. The amount of SN-pH 4.6 and SN-TCA did not show significant differences (P<0.05) between control (C1) and probiotic cheeses (LC and LCC) during ripening period. But during the 45 and 60 days of ripening, there were significant differences between C2 and others cheeses in the level of SN-pH 4.6 and SN-TCA. Lactobacillus casei without starter culture also could affect SN-pH 4.6. The gel electrophorotic patterns of casein break down during ripening showed that added Lactobacillus casei either in free or encapsulated forms with and without adding commercial starter was not effective in the αs1- casein breaks down in Iranian white chesses. The amount of FFA content in cheese samples containing Lactobacillus casei with no added commercial starter culture was similar to control samples. It can be concluded that Lactobacillus casei also can be effective on lipolysis in Iranian white cheese produced by ultrafiltration technique.

Drying of Mazafati Rotab (date) is an effective method to prevent its spoilage. This study was carried out by sun drying of Mazafati Rotab in a suitable place without contamination by birds and Rodents. At a 12- hour interval, date samples were selected for sensory and chemical analysis including moisture content, acidity, texture, shrinkage, skin separation and overall acceptability. The sun drying of Mozafati Rotab was done in Kerman, a city in Iran (1753.8 m above sea level) with an altitude of 56o 58´ and longitude of 30o 15´. The temperature, relative humidity, wind speed and the energy from sun's ray was from 6.6 to 38.5 oC, 5.3 to 27.4%, 0.0 to 6.9 m/s and 803.8 to 954.9 W/m2, respectively. The results indicated that by increasing the drying time-especially after 48 hours that the moisture content reduced below 22% (d.b.), the Rotab quality decreases and the acidity increases due to microbial activity. In order to reduce the Mazafati Rutab's moisture content to an optimal amount of 22% (d.b.) by open sun drying (OSD) under Kerman city climate, a drying time of 48 hours is recommended. Longer drying times will deteriorate the product's quality and its overall acceptance and the moisture contents of above 22% will make it susceptible to fermentation and souring of the Rutab.

Consumer demands have led to a renewed interest in using natural antimicrobial for food products. Biopreservatives such as essential oils and Probiotics have recently gained an increased attention to achieve an enhanced level of product safety and stability in food preservation industry. The study was designed to evaluate the antimicrobial effect of Mentha Longifolia L. essential oil in combination with Lactobacillus casei on Staphylococcus aurous in Iranian white cheese. The essential oil of this plant was obtained by steam distillation and analyzed by GC/MS. Effect of different concentrations of this essential oil and Lactobacillus casei on Staphylococcus aurous were determined by the growth culture on the selective media at different intervals of production, ripening and storage of Iranian white cheese. It was demonstrated that 0.03% and 0.015% of this essential oil had the highest inhibitory effect on the growth of Staphylococcus aurous when it was used in combination with Lactobacillus casei, and its reduction rate at the end of the storage period in experimental treatments were 1.89 and 2.32 Log more than the control group respectively. Furthermore, 0.015% of this essential oil combined with Lactobacillus casei has not only had the inhibitory effect on the growth Staphylococcus aureus but it also maintained concentration of the acceptable range. The synergistic effects between the above mentioned concentration levels of the essential oil and lactobacillus casei compared to the control and only essential oil was significant. Thus, the lower concentrations of essential oil can be used when it is combined with the probiotic to exert an inhibitory effect against Staphylococcus aureus.

The effect of fresh and freeze-dried sourdoughs containing Lactobacillus plantarum and Lactobacillus reuteri on sensory characteristics and crumb firmness of pan bread was studied. The freeze drying process significantly decreased the number of lactobacilli in the sourdough. Nevertheless, Lactobacillus reuteri showed more resistance to the drying process than Lactobacillus plantarum. Breads with higher loaf volumes and less moisture content were obtained when freeze-dried sourdough containing Lactobacillus reuteri was used. Crumb firmness increased upon storage for all the treatments. Both fresh and freeze-dried sourdough containing Lactobacillus reuteri produced bread with the least crumb firmness during storage. Sensory scores (after 72 h storage) for breads prepared from freeze-dried sourdoughs containing Lactobacillus reuteri were higher than those of other treatments. In conclusion, Lactobacillus reuteri can be regarded as suitable starter culture for production of dried sourdough.

Because of the harmful effects of the chemicals on human health and environment, the use of these compounds is recently restricted and it is necessary to use the safe compounds in postharvest technology of fruits and vegetables. In this study, the effect of  nitric oxide (NO; at concentrations of 0, 3, 5 and 8 µmol L-1) and putrescine (at concentrations of 0 and 2 mmol L-1) on postharvest life and quality of Selva strawberry fruit during storage at 2.5 oC with 85-95% RH for 15 days was studied. Fruit firmness, marketability, total acidity, total phenolic, vitamin C, total soluble solids, and color were evaluated. The treatment of fruit with 5 µmol L-1 NO significantly maintained fruit quality at the end of the storage. The treatment with a combination of NO and putrescine significantly prevented fruit softening. The results showed that NO and putrescine treatments preserved vitamin C and total phenolics. In addition, the results indicated that the use of NO and putrescine may be introduced as an effective and successful strategy in postharvest technology of the Selva strawberry fruit.