مجله علوم غذایی و تغذیه
سال هشتم شماره 3 (تابستان 1390)

The object of this study was to employ sourdough containing specific starter cultures and apply it for the production of Barbari bread and compare the quality of the product with the traditional Barbari bread which is produced in Iran. In this work four treatments of sourdough were prepared. In the first treatment as a control group, baker’s yeast (B1) was used. A mixture of Lactococcus lactis, Leuconostoc mesenteroides bacteria and baker’s yeast (B2), a mixture of Lactococcus lactis, Leuconostoc mesenteroides and the yeast Kluyveromyces marxianus (B3) and finally a mixture of Lactococcus lactis, Leuconostoc mesenteroides bacteria (B4) were used as second, third and fourth treatments. The quality evaluations of the texture of the samples were performed by application of Texture Profile Analyser (TPA) after 1, 2 and 3 days and the sensory evaluations were conducted after 1 day. The sensory evaluations revealed that there were not significant differences between B1, B2, and B4 groups while these groups had significant differences with B3 group in terms of appearance and crust. The B1 and B2 samples showed better porosity, chewiness and texture softness than the B3 and B4 samples. There was no significant difference (p
0.05) among the samples in term of odor and taste. The TPA analysis revealed that B2 and B3 samples were softer than B1, while the B4 was harder than the other groups. The application of the mixture of Lactococcus lactis, Leuconostoc mesenteroides bacteria and baker’s yeast (B2) is suggested to replace the traditional method (B1), on the basis of sensory evaluation and TPA analysis of the results.

Tomato is a product susceptible to physical vibrations and mechanical damages. Losses during harvesting, handling and transportation are considerable. In this research, the effects of different falling heights and type of falling surfaces on the shelf life and biophysical properties of tomato during 18 days of storage were investigated. Tomatoes; Rum TH 20163 variety were chosen and the effects of different falling heights, (0.30 and 60 cm) and kind of falling surfaces (wood, foam and plastic) on the shelf life and biophysical properties of tomato, such as density, packing factor, firmness, color and impact energy, during 18 days of storage, at 15ºC, were investigated. It might be concluded that falling height and time of storage period, increase the packing factor of the samples whereas increasing of falling height intensifies the impact energy, color changes and reduces the firmness of texture during storage. The results of this study demonstrate that foam surface inflicted the minimum impact damage on the fruits.

Belonging to the family of Lamiaceae, peppermint (scientifically called as Mentha Piperita L.) is a therapeutic and aromatic herb where the extract has various applications in food, cosmetic, hygienic and pharmaceutical industries. In the present paper, the essential oil of Mentha piperita L. is prepared by SFME method and its chemical and antimicrobial activities have been studied. The essential oil of dry plant was extracted, by hydrodistillation and microwave methods without using a chemical solvent. The chemical composition of the extracts were identified by GC/MS and compared against each other. The antimicrobial activity of each extract was tested on E. coli (PTCC 1330), Bacillus subtilis (PTCC 1254) and Salmonella typhinurium (PTCC 1622). For each essential oil the level of the minimum inhibitory concentration (MIC) was specified. The essential oil of Mentha piperita L. prepared by HD method contained 31 ingredients and the fraction prepared by SFME method contained 33 ingredients successfully identified. The results showed that MIC of both essential oils for the above microorganisms was 1000 ppm. Considering the results of the present research, it might be concluded that SFME method has some advantages namely reduction of extraction time, increase of extraction yield, decrease of energy and water consumption and production of higher percentage of active ingredients.

E.coil O157:H7 is one of the main factors leading to food toxicity anddiseases such as diarrhea, bleeding coliris, uremic hemolytic syndrome, thrombocytopenicpurpura and even death in man. Enrichment was made in two stages by lactose broth and selenite cystein and then cross over was made on chrome agar E.coil O157:H7 media. The purplecolor colonies represent the presence of this microorganism. It is worth to mention that the chrome agar specific culture media acts selectively and dose not have the problems of mechanical agar sorbitol culture media. The positive separated cases underwent confirmation tests detection by multiplex PCR. In this method, STX1 and STX2 genes were separated. The products consisted of premium hamburgers (after 3 months of production) and ordinary hamburgers (after 48 hours, 3 months and 6 months of production). The findings obtained by m-PCR diagnostic test and culture on chrome agar indicated high contamination of tested meat products, that might be due to various reasons namely failure to follow up the health procedure and mechanism and the addition of illegal additive to the products. We suggest strict microbiological tests to be carried out and E.coil O157:H7 tests become mandatory in meat production plants.

Due to the unfavorable smell of the accumulated sugar beet wastes in the factory and its mixture with the lime wastes, it is costly and uneconomic to dispose this mixture. This research has been performed to investigate the possibility of producing compost and vermicompost from the waste in sugar beet factory in Qazvin. In order to produce compost, sugar beet wastes were collected. Temperature, moisture and aeration were controlled during production period. The quality of compost was examined by carrying out a series of quality control tests concerned with ripening degree. The initial results indicated an initial increase in temperature to over 60oC due to intensive activity of microorganisms. The temperature decreased gradually and reached the environmental temperature after two months. In order to investigate and control the quality of the produced compost, ripening degree of compost was calculated. Comparing the experimental results with the standard indices of ripening degree showed that the product is suitable in terms of temperature variation, cress, and percentage of Ammonium-Nitrate. Apart from the above findings, the produced vermicompost was suitable in terms of ripening degree. The produced vermicompost was superior to the compost produced from sugar beet wastes in terms of chemical characteristics, i.e., Phosphor in vermicompost increased 3 times as compared to compost while saltiness decreased by 50%. Zinc and Nitrogen were also increased.

Drying is one of the most important step in raisin processing. Temperature, air velocity and pretreatment are important factors in grape drying process and the quality of final product. In this research, the effects of the following conditions on the quality of Thompson seedless raisin were studied: temperature at four levels of 50, 60, 70, and 80ºC, air velocity at three levels of 1, 2 and 3 m/s, and four pretreatments consisting of hot water, %5 potassium carbonate, with %0.4 olive oil, %0.5 sodium hydroxide and no pretreatment. The results indicated that factors such as temperature, air velocity and pretreatments have significant effects on browning rate and rehydration. Similarly temperature and pretreatment factors have significant effect on acidity and only temperature factor has significant effect on shrinkage. Raisins dried at 60 and 70ºC and pretreated in hot water, %5 potassium carbonate and %0.4olive oil and %0.5 sodium hydroxide provided better quality.

Phospholipids, might be regarded as preventive antioxidant and some mightexhibit synergistic effects on the oil stability. It is the aim of this research work to examinethe antioxidant and carry through properties of some phospholipids in fractionated sheep tailfat, the olein fraction. In this research work, antioxidant activitiy of some phosphatides namely phosphatidyl choline, phosphatidyl ethanolamine and phosphatidic acid (Sigma Chemical Company) were studied in mutton tallow, the olein fraction at 150°C, by induction period measurements. Rancimat apparatus was employed as a mean to evaluate the induction periods of the samples. Carry- through properties of selected phospholipids was calculated by detection of Standard Coefficient. The results showed that the addition of phosphatidyl choline and phosphatidyl ethanolamine slightly increased the oxidative stability of tallow olein while phosphatidic acid showed no antioxidant effect. Antioxidant activity of phosphatidyl ethanolamine was more than phosphatidyl choline at low temperatures. Antioxidant activity of phosphatidyl ethanolamine decreased faster than phosphatidyl choline as the temperature was increased. Therefore Standard Coefficient of phosphatidyl choline is greater than phosphatidyl ethanolamine.

Listeria monocytogenes is notable among the pathogens which cause food – borne infections because of the high incidence of fatalities in those who develop systemic infection. The aim of this study is to determine the antimicrobial resistance pattern of Listeria monocytogenes isolated from fresh cheese in Marvdasht. In this cross- sectional and descriptive study 428 fresh cheese samples were collected from 4 areas of Marvdasht during May to September 2007. All the samples were transferred to enrichment media and then cultured in various types of selective media. Biochemical tests were employed for identification of suspected bacteria. Finally, antibiotic resistance of isolated Listeria was evaluated by using CLSI. Out of total collected samples, Listeria monocytogenes was isolated from 56 samples (%13.08). The most frequency of isolated bacteria were in Kamfiroz (%4.67), Dorodzan (%3.97), Markazi (%2.57) and Seydan (%1.89) respectively. Fisher test indicated significant correlation between months of sampling and Listeria monocytogenes isolation (p = 0.004). All the isolated Listeria had sensivity to Ampicillin and most resistance was observed for Tetracycline and Ceftriaxone. The results indicated a notable contamination of fresh cheese with Listeria monocytogenes in Marvdasht.

One of the most important problems in kilka meal factories is stick water production, as a waste, from meal production process. Five hundred litters of stick water is produced for each 1000 kg of kilka fish. This waste has rather high protein and might be used as substrate for the growth of bacteria such as lactic acid bacteria. In this study Lactobacillus bulgaricus and Lactobacillus plantarum were used for SCP production from stick water. Adaptation of Lactic AcidA bacteria to pure stick water was performed by increasing the concentration of stick water in distilled water. The growth of bacteria was studied by spectrophotometric method and reading the optical density of bacteria at 600 nm. The effect of glucose, as additional substrate on SCP production, was also evaluated. After separation of biomass, the final product was lyophilized by freeze dryer and then was analyzed for amino acid profiles, total protein, total fat, moisture and ash.The results showed that the amount of produced SCP from L. plantarum and L. bulgaricus were 13-15 g/l and 16-19 g/l in normal stick water and 20-22 g/l and 21-25 g/l in the presence of glucose respectively. Mean value of total protein, total fat, moisture and ash in produced SCP were 82.26%, 1.02%, 0.54% and 15.58% whereas the percent of these values in stick water were 5.15%, 2.26%, 92% and 0.57% respectively. The results showed that amino acids composition in produced SCP is comparable with the suggested pattern of requirement by FAO/WHO.

Dehydration is one of the methods employed for food preservation. In this study the effect of drying on the quality characteristics of apricots consisting of browning, shrinkage, rehydration, hardness and residual sulfites has been investigated. Ripened apricots with 83- 87% initial moisture content were employed. Statistical analysis concerned with the effect of heat variations on quality indices namely browning, water absorption, texture hardness and residual SO2 were carried out using MINITAB and SAS software. The results indicated that the effects of drying methods on browning, rehydration, residual sulfite of dried apricots were highly significant, but the methods had no significant effects on shrinkage and hardness. This investigation indicated that hot air drying at 60oC was found to be the most suitable condition.