IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2004 | Volume:1 | Issue:1|Papers Count:8

Microencapsulation is defined as the technology of packaging solids, liquids or gaseous materials in minature (diameter between 1 and 1000 mm) in which the sealed capsules can release their contents at the controlled rates and under the specific conditions. Microencapsulation of cream is among those methods that can be used to prevent its oxidation and therefore increase its shelf life. Many researches have been carried out on the microencapsulation of cream (it has many applications in various food industries) and results indicated that the limited number of coating materials have been successfully used for the encapsulation of cream. In the present work, whey powder containing approximately 12% of protein was used as the main wall constituent. Gluten gelatin refined starch and licorice extract were also used in varying amounts as a partial replacement for the whey powder in the wall formation. Cream was used as the core material and the spray drying technique was used for the microencapsulation process. The effects of the type and the concentration of the wall materials as well as the amount of the core material on the microencapsulation efficiency and microencapsulation yield were investigated and the results were reported. 

Effect of frying conditions was studied in color changes of French fries potatoes in deep-fat frying. Color scale has been chosen as a parameter to evaluate color changes due to the temperature of fat, kind of fat and the thickness of potatoes slices. After blanching in water bath for 5 to 15 minutes at 70-85oC, they were soaked into the solution containing: 0.4-0.8% of caramel, 0.02-0.08% of turmeric, 0.3-1.4% of dextrose and 0.5-2.2% of sodium acid pyrophosphate. The results showed that the lightness of the color increased at the beginning of the frying stage and then, it remained constant. As the thickness of the potatoes strips decreased, the lightness of the color decreased. The best results obtained at the temperatures below 170°C with the lighter color.

Milk is considered as a main foodstuff and is of great importance in the countries where the contamination of this foodstuff to bacteria such as yersinia entrocolitica and listeria monocytogenes can be very harmful to people. In this research, we tried to study the contamination of milk to these bacteri. Therefore these 200 samples of raw milk and 200 samples of pasteurized milk were provided through cluster random sampling and then, they were tested bacteriologically. After bacteriological experiments, 3 (1.5%) listeria monocytogenes and 6 (3%) yersinia entrocolitica were found in the 200 samples of raw milk. No listeria mohlocytogenes was found in the 200 samples of the pasteurized milk but 2 (1%) yersinia entrocolidca were found. Based on the results obtained from different countries (and also iran) regarding this bacterium it is highly recommended to consider the importance of exact and correct principles of pasteurization and not to use raw milk.

The main goal of this interventional study was to evaluate the antibacterial effects of the volatile oils of some plants including thyme (Thmus Vulgaris), Tarragon (Arlemisia dracunculus), Caraway Seed (Caram Carvi), Penny royal (Mentha pulgium) and peppermint (Mentha piperita) in cheese. Therefore, their volatile oils were extracted using steam distillation methody and from the two concentrations close to the level of MIC of each herb's volatile oil (Thyme 0/1% and 0/2%, the others 0/3% and 0/4%), some 106 CFU/g sacteria (E.coli k12) were inoculated into the sample and control cheeses. All sample and control cheese were kept at 12ºC (Optimum temperature for ripening of cheese) for one week and were checked for the number of sacteria after 24, 48, 78 and 168 hours. The results also indicated that the volatile oils of Thyme caused 3 and 4 log reduction of E.coli at 0.1 and 0.2% concentrations in the samples after 168 hours. The oils of Peppermint, Carawey seed and Peny royal showed moderate effect and caused 2 and 2.5 log reduction at 0.3 and 0.4% concentrations to the control after 168 hours. The volatile oils of Tarragon caused 1 and 1.5 log reduction to the control at 0.3 and 0.4% concentrations after 168 hours. According to the results of this study, it is applicable to use these volatile oils as the natural preservatives and flavoring agents in cheese.

Olive fruit has enzymes which can affect the quality of its oil. In this research, the effects of blanching on the quality of the oil, oil yield, chlorophyll and polyphenols at 92oC for 1, 2, 3, 4, 5 and 6 minutes and also keeping the fruits for 15 days at room temperature were studied.Results showed that the heat treatment reduced acidity. Increasing the time of blanching increased the chlorophy content of the extracted oils which in turn increased its peroxide value. Insufficient blanching reduced total polyphenols of the oils extracted from the fruits. Heat treatments and the time of keeping of the fruits had significant effects (99% confidence) on the oil yield, but the reaction of these two factors was not significant at 95% confidence. Increasing the time of blanching and also keeping of the fruits increased the oil yield.

In order to compare the effects of 2 packaging methods (normal and vacuum packing) and their combinative effects with 1% lactic acid spray on the shelf life of mutton, 8 samples of meat from 8 carcass were taken and each sample was divided into two portions and treated with lactic acid spray and another two without any treatment four portions. Then the samples were packed and kept in chilled room at 3oC. They were taken out tegining from the 4th day (with 3 days intervals), and examined for chemical (pH, TVN), microbial (total count, coliform and total anaerobe counts) and organoleptic test (weep loss percent, color and oder status). Overall, it was concluded that the amounts of the assessed chemical and microbial parameters (other than total anaerobic counts) of normal packaged meat were higher than those of the meat in the other methods of packaging (P<0.05). Total anaerobe count of the vacuum packaged meat was higher than the normal packaged meat (P<0.05). The lowest level of weep loss of meat was occurred in the normal packagings. On the other hand, the worst quality of the color and odor status was distinguished in the normal packaged meat during the storage period, however the best color and odor status of meat was occurd in the vacuum packaging (until the 10th day). All kinds of the packaged meats had undesirable color and odor after 15 days of storage. In normal packaging, the chemical and microbial paremeters of the treated meats (by 1% lactic acid) were differed significantly from those of the untreated meat (P<0.05), but this difference was not significant in vacuum packaging. Considering the obtained results of chemical, microbial and organoleptic tests and taking in to account of the permitted level of TVN (19.7 or 20 mg/100) and the total count (107 CFU/g), according to National Iranian Standards, it was estimated that the shelf lives of meat in the normal packaging and vacuum packaging were four and 10 days, respectively. Additionally, because of the convenience of chemical and microbial parameters in the normal packaged meat sprayed by 1% lactic acid, this treatment is recommended to improve the keeping quality of normal packaged meat.  

Protein as a nutrient and functional ingredient has a vital role in the metabolism of body. Athletes and those who have to lessen their body weight need more protein than the ordinary people. Soy protein isolate (SPI) is a good source of protein and contains all of the essential amino acids, but it has some limitations for using. In this study, the effect of xanthan and carrageenan on the qualitative properties of foaming of SPI (i.e. foam stability, foam capacity, solubility and viscosity) were studied. Therefore, combination of xanthan (X) in the levels of 0, 0.04, 0.09, 0.13% and Carrageenan (C) in the levels of 0, 0.03, 0.07, 0.09% were used. Statistical results showed that xanthan and carrageenan had significant effects on the foam stability, foam capacity, solubility and viscosity. The results also showed that foam stability was occurred at the higher amounts of xanthan and carrageenan (X=0.13%, C=0.09% and X=0.09%, C=0.09%), while in the less amounts of xanthan and carrageenan (X=0.04%, C=0% and X=0.04%, C=0.03%), the highest capacity of foam was observed. The highest solubility of foam was occurred in the higher amounts of xanthan (X=0.13%, C=0%, X=0.13%, C=0.07%, X=0.13%, C=0.09% and X=0.09% C=0.09%). It means that combination of xanthan/carrageenan is important which affects the solubility and foaming properties of SPI. The results showed that foam stability does not relate to foam capacity.  

The effect of different hydrocolloids (guar‚ loucast bean‚ xanthan and carboxy methyl cellulose) on rheological properties of wheat flour dough and the final quality of Lavash breads was investigated. The study of rheologyical behavior of dough containing hydrocolloids was performed using farinograph‚ extensograph and falling number. Water absorption was slightly increased by hydrocolloids. This result was expected due to the well-known water holding capacity of hydrocolloids. Rheological characteristics of wheat flour dough were modified to different extent by hydrocolloids with varying chemical structures. The greatest effect‚ but not the test‚ at dough level were promoted by xanthan followed by guar. Generally‚ hydrocolloids strengthen the wheat flour dough. The final quality of Lavash breads was determined by panel test. The data obtained from panel group for breads with and without hydrocolloids‚ indicated that the hydrocolloids delayed the bread staling specially with guar gum. In contrast‚ the hydrocolloids increased the moisture retention and water absorption especially with xanthan and guar gums. In addition, textural studies revealed that the addition of guar gum reduced the firmness of bread. The data of both dough rheological properties and bread quality drive us to conclude that guar gum has good properties to be used as improver in baking of Lavash bread.