IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2005 | Volume:2 | Issue:3|Papers Count:9

This study carried out to determine the antifungal effect of some plant essential oils (Thyme, Tarragon, Caraway seed, Peppermint and Pennyroyal) on industrial white cheese. Two concentrations (0.3 & 0.4 %) were added in white cheese, which their fungal population was determined previously. For comparison purpose, identical cheese sample without any essential oils were chosen as control groups. All of the samples and controls were kept in 12 oC for 2 weeks, and checked for fungal population at 72, 168 and 336 h intervals. The results showed that the population of fungi grew in control groups and reached to a level of 104cfu/g after 336 h, but in treatment groups the essential oils of the examined plants showed desirable antifungal effect. The essential oils of the Thyme and Tarragon showed the most effective antifungal activity and inhibited the growth of fungal population completely, where as the others could not control the growth of fungi completely, although the final fungal population after 336 h were within the standard range (102cfu/g).  With regard to our finding, the essential oils of the examined plants have desirable antifungal effect on cheese and can probably be used as a natural preservative in foods.

In tropical and dry farming areas, in some seasons, wheat use after harvesting with out any delay to obtain its optimum quality. This wheat can’t be used industrially, because have no essential gluten matrix. Furthermore flour and bread which is made, have no enough quality and a lot of it will be wasted. During this project five kind wheat [Azar2, Dez, Sardari, Showa and Star] is tested. The results shown that the storage of them for 50-60 day after harvesting can improve qualitative specifications of this kind such as; zeleny, gluten index, dough resistance, water absorption, valor metric value and bread volume. According to this, storing wheat for 50 – 60 day after harvesting is essential for having optimum gluten matrix and wheat quality for baking and is offered.

Frying oils undergo quality changes due to long term heating at high temperature in the presence of oxygen and moisture. The aim of this study was determination of fry-life of two formulated frying oils produced in pilot scale. After determination of physical and chemical characteristics of primary oils, two formulations, i.e. formula 1 or F1 (palmolein and sunflower oils 50:50) and formula2 or F2 (palmolein, sunflower and cottonseed oils 50:25:25) were prepared by blending, then TBHQ (100ppm) and citric acid (100ppm) were added to them. For determination of fry-life potato slices (Agria variety) were fried at a rate of 200g/30 min (180 °C) in a 40-litter fryer, until one of the characteristics (peroxide value or PV, acid value or AV, smoke point, total polar compounds or TPC, Fritest and Rancimat) reached the discard point for frying oil .PV were variable due to decomposition in high temperature and reproducing during cooling of the oils .AV and TPC were increased during frying. The increasing of AV was higher in control, reversely two formulated frying oil's TPC were more than control .A sample of partial hydrogenated frying oil produced by an Iranian factory was used as control. Oxidative stability of two formulated frying oils and control were determined by Rancimat in 110°C. Oxidative stability of frying oils were reduced during frying as well as smoke point , although this reduction was faster in control, and after 25hrs frying reached the discard point (178 °C) .The results of Fritest were not similar to TPC in the last steps. Statistical analysis did not show a significant difference (P<0.05) in the fry-life of F1 and F2 (TPC of F1 and F2 were 21 and 20.5 hours, respectively) but there was a significant difference between two formulated frying oils and control (P<0.05). The control was discarded after 26.5 hrs frying. Regarding the fry life, nutritional value (especially trans fatty acid content) and economical aspects (cost of hydrogenation) ,F1 was the best frying oil(F1>F2>control)and could be suggested as a substitute for hydrogenated frying oils.

In this research, a gravity separator apparatus was used for separating Sunn Pest–Damaged Wheat from good wheat. Influence of parameters of machine table (longitudinal and latitudinal slopes, oscillation frequency and amplitude and velocity of air) for obtaining of maximum separation of Sunn Pest–Damaged Wheat from good wheat has been studied. Using of dimensional analysis and a model study that is common in fluid mechanic, some dimensionless parameters were produced that were effective in reduction of numbers of parameters. Results showed that increase of latitudinal slope of table from 0.5 to 2 degrees and reduction of longitudinal slope from 5 to 3 degrees increased separation of Sunn Pest–Damaged Wheat. A dimensionless number v/aω which shows ration of innercy force of air current blown to wheat to force arising from oscillation was considered in ratio of separation. The results of the experiment showed that the separation of Sunn Pest–Damaged Wheat get to maximum 95.14 percent in  v/aω=152.3 longitudinal slope 3 degree, and latitudinal slope 2.

Artificial drying of agricultural products is one of the most common methods of preservation. Proper drying procedures eliminate the extent of spoilage during subsequent storage and increase the shelf life of the product. Controlled the drying process is important for improving dryer design. A finite element method is used to obtain numerical solutions to the simultaneous moisture equation describing the moisture removal process for isotropic sphere and axisymmetric ellipsoid. It assumes that moisture diffuses to the outer boundaries of the kernel in liquid form and that evaporation takes place only at the surface of grain. Thin layer of wheat dried at 35, 45, 50, 60 and 70 ºC temperatures. The least and the most values of Root Mean Square Error between sphere model and experimental data are 0.02984 and 0.04973 respectively and between ellipsoid model and experimental data are 0.00971 and 0.02021 respectively. Simulation of ellipsoid model results agreed well with the experimental data of thin layer drying. So ellipsoid model for simulation of mass transfer in wheat kernel during drying can successfully be used.

This research has been done to find out optimize process conditions for producing pomegranate juice powder by spray dryer. To do so a pilot scale spray dryer was used and the effects of different parameters were determined. The result show that Malt dextrin with De=6 as drying aid with fruit juice to Malt dextrin ratio equal to 65/35 and %0.3 zincstearate for free flowing state give best product quality. Dryer chamber temperature was 120 degree of centigrade, atomizer rpm was 1400, input to output air temperature was 170/103 and feed flow rate was 36 CC/MIN. Properties of pomegranate juice and pomegranate juice powder were analyzed and has been reported.

Chitosan, a deacetylated derivative of chitin, is found in crutacean, arthropod, cell walls of some fungi, fish shell and shrimp shell. The objective of this research was to investigate the effectiveness of chitosan (extracted from shrimp shell) as a stabilizer and thickener and to compare its textural effects with commercial chitosan and carboxymethyl cellulose (CMC) in mayonnaise. In this study chitosan was produced by chemical method from shrimp shell. The percent recovery of chitosan from shrimp shell on wet basis was 17%.Protein and ash contents and degree of deacetylation of the produced chitosan were determined and compared with commercial chitosan. The effect of different concentrations of chitosan on rheological properties of mayonnaise in comparison with commercial chitosan and CMC were investigated. The emulsion stability and viscosity of mayonnaise samples at different chitosan concentrations (0.1, 0.2 and 0.3%) were determined. At 0.3% concentration the highest viscosity of mayonnaise was achieved. Also the results showed that mayonnaise containing 0.2% of produced chitosan can have the same viscosity as commercial mayonnaise (containing 0.2%CMC). Sensory evaluation by panelists proved that in term of texture, there are no any significant differences between the mayonnaise samples containing different concentrations of produced chitosan and commercial chitosan. This investigation demonstrated that chitosan can be used in mayonnaise and other similar emulsion products as a new stabilizer and thickener agent.

Application of high isostatic pressure in biological and food researches has been extensively studied in the last decade. It has recently been proposed that high isostatic pressure might be applied to increasing both the activity and stability of several enzymes. In this research the enzymatic activity, CFU and morphological changes of commercial S.cerevisia under 0, 50, 75, 100, 125 and 150 MPa pressure at 5, 10, 15 minutes pressurization after 24 hours keeping in 4C° were studied. The results statistically analyzed and showed that 50 MPa pressure didn’t affected on yeast cells but increased the enzymatic activity in 75 and 100MPa pressure at 10 and15 minutes pressurization. In addition the images of scanning electron microscope (SEM) showed that despite of increasing activity of enzyme the structure of yeast cell walls changed and hollowed in 100MPa pressure. The enzymatic activity and CFU (1log.) significantly decreased in 125 and 150 MPa. Inactivation of yeasts and decreasing the enzymatic activity can be due to morphological changes of yeast cells by induced high pressure. The images of scanning electron microscope (SEM) after one month pressurization and keeping in 4C° showed that all of treated yeast cells were destroyed.