مجله علوم و صنایع غذایی ایران
سال نهم شماره 2 (پیاپی 35، تابستان 1391)

This project was carried out in order to increasing of shelf life of Kilka Fish and prevent of color changes during cold storage. Edible film made by sodium alginate (1. 5 and 2% concentrations) was used for fish packaging at time 0. Cleaned Kilka fish was packaged in disposable dishes and covered by cellophane was used as control samples. The samples were kept at -18oC. Examinations were carried out for a period of six months. No statistically significant difference was observed in total bacterial counts nad staphylococcus bacteria in the covered samples compared with the control samples (P>0. 05). Coliform، Escherichia coli and Pseudomonas bacteria contamination were negative until the end of storage period in the samples. No statistically significant difference was observed in protein، lipid and ash in test samples compared with the control samples. Statistically significant difference was observed in free fatty acids، thiobarbitoric acid، Peroxide value، TVN and pH in test samples compared with the control samples. Statistically significant difference was observed in moisture in the covered samples compared with the control samples (P> 0. 05). Sensory analysis carried out to Ranking method. Statistically significant difference was observed in overal acceptable in the covered samples compared with the control samples. Statistically significant difference was observed in this index in the covered samples with 1. 5% concentration compared with the covered samples with 2% concentration. Covered samples with 1. 5% concentration had better quality compared with the covered samples with 2% concentration. The covered samples had a favorable quality until the end of storage period. But، the control samples had a favorable quality for a period of three monthes.

Using well method and Macrodilution technique، the effect of annatto extract (norbixin 1%) on growth ability and spore germination of several pathogenic bacteria (Staphylococcus aureus، Bacillus sereus، Clostridium perfringens and Escherchia coli) was investigated. According to the results emerged from inhibition zone diameter evaluation، the annatto extract showed inhibitory effect on S. aureus، B. sereus and C. perfringens (with 13، 12 and 10 mm inhibition zone diameter، respectively)، but it was inactive against Ecoli. The outcome of Macrodilution technique indicated that the minimum inhibitory concentrations in 106، 104 and 102 cfu/ml of S. aureus and B. sereus are 1. 2، 0. 6 and 0. 3 g/l of the annatto extract. The concentration values، however، are 2. 4، 1. 2 and 0. 6 g/l at the same cfu/ml of C. perfringens. In addition، the abovementioned concentration values of annatto were capable of inhibiting spore germination of B. sereus and C. perfringens. As an overall result، annatto can be used as a natural antibacterial food additive in many food products.

In this research، the effects of different levels of retentate fat (0، 2، 6، 10، 14 and 18%) and CaCl2 (0 and 0. 02%)، on the coagulation (coagulation time، whey amount and yield) and chemical characteristics (fat، total solids، acidity and pH) of UF-Feta cheese made from retentate powder were studied. Furthermore، the effects of salting manner (addition on special paper after coagulation or direct addition to retentate)، on the coagulation and chemical characteristics of full-fat sample were investigated. The statistical analysis showed that، the coagulation time and whey amount were increased with fat reduction، whereas the yield was decreased significantly (p < 0. 05). Adding CaCl2 had significant (p < 0. 001) reducing effect on coagulation time and this effect was more observable in cheese samples with fat levels lower than 10%. The effects of CaCl2 on whey amount، yield and chemical properties were insignificant. On the other hand، fat reduction had significant effect on all the chemical properties. Maximum fat content، total solids and acidity; and minimum pH were observed in cheese sample that made of 18% fat retentate so that، differences with other treatments were significant (p < 0. 05). The addition of salt directly to retentate (without using of special paper) decreased the total solids and whey amount and increased yield، but pH and acidity didn’t show significant differences.

Listeriosis، an infectious disease caused by eating contaminated food with the bacterium Listeria monocytogenes، has been recognized as an important public health problem. The disease affects primarily pregnant women، newborns and adults with weakened immune system. With the aim of using plants essential oil as natural antibacteria، the effect of Cumin (Cuminum cyminum) essential oil (in 0/02% and 0/04% concentration) was studied on Listeria monocytogenes in Iranian white cheese as a food model inoculated with 10³ cfu/ml in milk consumed for cheese making during 60 days storage period and compared with the blank sample which was not contained essential oil. According to results Listeria monocytogenes after 1 log reduction was not isolated from cheeses containing 0/02% and 0/04% Cumin essential oil after 30 and 15 days of storage time respectively. But in cheese without Cumin essential oil (0%)، the bacterium was isolated during the period of study. Statistical analysis with Repeated Measures Define in SPSS 16 showed significant difference between all treatments (p<0. 05). Also One-Way ANOVA showed that the difference of bacterial loads (Listeria monocytogenes) after 7th day of storage was statistically significant (p<0. 05). These results showed that Cuminum cyminum essential oil has antibacterial effect on Listeria monocytogenes

In this study، phenolic compounds of acorns (Q. castaneifolia var castaneifolia) were extracted with water and ethanol (70%). Total phenolic content of water and ethanolic (Et) extracts were 238. 85 and 142. 18 mg TAE/gr dried extracts، respectively. Antioxidant activity was evaluated using three different including scavenging effect on DPPH radicals، reducing power of Fe+3 and total antioxidant capacity. The results were compared with synthetic antioxidant، BHA and BHT. In all the methods، the antioxidant activity was concentration dependent. Ethanolic extract of Q. castaneifolia was the highest in DPPH assay (EC50=34. 28 µg/ml). In the reducing power and total antioxidant capacity، BHT obtained the best results followed by ethanolic extract، BHA and water extract. Also، the protective effect of ethanolic extract in stabilizing sunflower oil was tested. Ethanolic extract of acorn at three different concentrations، i. e. 250 (Et-250)، 500 (ET-500) and 1000 ppm (Et-1000) was added to sunflower oil. BHA and BHT at 100 and 200 ppm were chosed as standards along with the control. All samples were incubated in open beakers at 70°C in the dark for 12 days. The peroxide and tiobarbitoric acid values of the samples were determined at definite time intervals of 0، 2، 4، 6، 8، 10 and 12 days. Results showed that ethanolic extract at all concentration retarded the retarded the oil oxidation. Et-1000ppm and Et-500 ppm exhibited stronger antioxidant activity compared to BHT-200 and Et-250 was better than BHA-100.

Mastitis is one of the most common diseases that can affect composition of milk and hence the products derived from it. In this study oscillatory rheological tests were carried out to determine the effect of somatic cell counts (SCC) on viscoelastic properties of strained yoghurt. Results of strain sweep tests showed that by increasing SCC in samples، structural strength، yield stress، flow point and dependence of elastic modulus (G¢) to strain outside of linear viscoelastic range (LVE) were decreased. Frequency sweep test results revealed that for all samples elastic behaviour dominates the viscous one over the whole range of frequency but by increasing SCC، G* decreased and G¢ became more frequency dependent which means a weaker and also less gel structure، for samples with higher SCC. It was indicated that somatic cell count of milk is a critical factor which affects the quality and yield of strained yoghurt

The chemical composition of the essential oil of Cinnamomum zeylanicum (Nees) that has been used in food indusries were analysed by GC–MS and 21 components were detected. The major component characterized in the essential oil was E-cinnamaldehyde (60. 41%). The other components were linalool (6. 46%)، Ortho methoxy cinnamic aldehyde (3. 63%)، βcaryophyllene (3. 5%)، 1، 8-cineole (3. 32%)، Eugenol (3. 19%) and etc. The antimicrobial activity including minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of cinnamon essential oil were evaluated against five food born pathogenic and spoilage bacteria including Listeria monocytogenes، Escherichia coli، Pseudomonas fluorescens، Lactobacillus plantarum and Lactobacillus sakei. The MICs of cinnamon essential oil against L. sakei and the other bacteria were observed 250 and 500 µg/ml respectively. The MBC of cinnamon essential oil against Pseudomonas fluorescens and Lactobacillus sakei was 1000 µg/ml. The MBCs for the other bacteria were more than 1500 µg/ml.

The effects of turmeric extract on the shelf life of whole، vacuum-packaged rainbow trout، stored under refrigeration (4±1◦C) were studied by monitoring the microbiological (total viable count، psycrotrophic)، chemical (PV، TBA، FFA)، pH and sensory changes for a Period of 20 days. Turmeric extract significantly (p<0/05) delayed lipid oxidation in treated samples. psycrotrophic bacteria and total viable count of treated samples with turmeric extract maintained lower than the proposed acceptable limit (7 log cfu/g) as far as microbial spoilage significantly (p<0/05) decreased in turmeric samples in comparison with the control samples. According to sensory and microbial analysis turmeric samples in compare with the control samples were acceptable for eat to end of storage.

Edible films and coatings are used to protect food products and improve their quality and shelf life. The objective of this study was to evaluate the effect of two methyl cellulose- based active coatings on the quality and storage life of tomato. Fruits were dipped in to active methyl cellulose (MC) coating (MC، glycerol and potassium sorbate) or active MC-palmitic acid coating (MC، glycerol، potassium sorbate and palmitic acid) for 1min at 20oC، then air-dried at room temperature and stored with uncoated samples at 15 oC and 80-85% RH for 21 days. At one day intervals، coated and uncoated fruits were removed and evaluated for weight loss، total soluble solids، titrable acidity، pH، skin color، firmness، failure energy، ascorbic acid content، yeasts and moulds count and overall acceptability. It was revealed that the coated fruits showed lower weight loss (up to 2. 5 times)، ripening rate، spoilage incidence (2-3 times) while، the skin color، ascorbic acid content، sensory quality and overall acceptability were higher in coated tomatoes when compared with control during storage time. However، non significant differences in the properties of tomato were observed by adding palmitic acid to the formulation of MC active coating.

In this study a number of 100 hamburger samples which were produced industerially from different batches were collected randomly from suprermarkets in Mashhad city، during the autumn months of 2006. For isolation of the bacteria، samples were، firstly enriched in modified trypticase soy broth containing novobiocin، followed by plating on sorbitol Mac Cankey agar supplemented with cifixime and potassium tellurite. Consequently the suspected non sorbitol fermenting (NSF) colonies were confirmed by biochemical tests as Escherichia coli and then employed for multiplex-PCR assay، using primers specific for O157 and H7 antigens gene. The m-PCR assay employed in this study may be a possible alternative to immunological assays which detects somatic and flagellar antigens. In this study، 9 NSF Escherichia coli colonies were isolated، and in multiplex-PCR assay two samples (4%) were confirmed as Escherichia coli O157: H7.