نشریه پژوهش های علوم و صنایع غذایی ایران
سال چهارم شماره 2 (پیاپی 8، نیمه دوم سال 1387)

In Iran, the majority of vegetable oil producers, use PET for packaging their products. Due to high solubility of PET oligomers in the oils, and shelf life of liquid oils, it is expected that some compounds migrate into the oil. This study was carried out to determine the amount of migration of terephtalates from PET bottles into sunflower oil and the effect of temperature and storage time on the degree of migration. 42 samples of liquid sunflower oil packed in one litre PET bottles, from single production bach of pars vegetable oil, were kept at 20˚C and 40˚C. Experiments were carried out on three bottles taken at different periods of time (10, 20, 30, 70, 145 & 202days). According to Castle method, alkaline hydrolysis of all PET oligomers to terephthalic acid followed by its methylation to dimethylterephthalate (DMT) for the measurement of DMT, derivative UV spectrophotometer was used according to Reeves.The results showed that the maximum level of migration of terephthalates at 20 ˚C was 29.43 + 0.93 and at 40˚C was 29.58 + 1.15. Therefore the amount of overall migration obtained in this research is lower than the international permitted level (lower than 60 ppm) and sunflower oil after the final migration can be safely consumed. Migration increased with the passage of time until it reached to its highest level and then stopped (P=0). Migration is faster when the temperature is increased (P=0.014). Therefore, migration is dependant on both temperature and contact time (P=0.001). In this research, linear dependence between migration and square root of time has also been demonstrated (r = 0.96 at 20 ˚C from time zero to 145 days and r = 0.95 at 40˚C from time zero to 70 days). Reproducibility of the method was evaluated by calculating the relative standard deviation which was equal to 3.21% and the detection limit of the method was 0.21 ppm. In conclusion migration of PET oligomers was dependant on time and temperature, until it reaches an equilibrium.

In this work, the effects of acetic and lactic acids addition to rice during cooking, on the texture and morphological properties, and too, the gelatinization temperature (GT) of the cooked Domsiyah rice was investigated. All experiments were carried out in triplicate and data analyzed in randomized completely by SPSS15 software. The results showed that acid addition to rice during cooking cause a decrease in firmness and GT, but had no significant effect on adhesiveness of samples. Also, the results of the scanning electron microscopy on the outer surface of cooked rice kernel revealed that the acid's addition to rice during cooking cause a reduce in pore size and porosity. According to amylography and SEM results, it seems that acid's addition to rice during cooking, cause the better gelatinization and closer pores on the outer surface of cooked rice. The results of this research can be used in improving in quality attributes of cooked rice and other products that contain rice flour and rice starch, according to the aim and application of the desirable product.

Usage of different lactic acid bacteria strain is one of the reduction methods in phytic acid content of bakery products. In this study the effect of making sourdough with L. plantarum and L. reuteri with DY=160 and DY=200 and replacement ratio 10, 20 and 30% instead of flour in dough formulation on phytic acid content of Lavash bread was investigated. The highest decrease in phytic acid content is related to using sourdough involved L. plantarum with DY=200 and 30% replacement of sourdough (44.06%).Usage of sourdough causes flavor and chew ability modification in bread. The best flavor is related to bread which is made of sourdough involved L. plantarum with DY=200 and 30% replacement. But biophysical properties containing texture, form, shape, and up and down surface in this sourdough application gain lower score than bread which is made of yeast.

In this study, physicochemical and organoleptical properties of muffin cake prepared by substitution of egg white with different levels of whey protein concentrate (WPC) and different levels of guar and xanthan gums in the furmolation were evaluated.WPC at three levels; 25, 50 and 75 %, guar gum at two levels; 0.1 and 0.3 %, and xanthan gum at two levels; 0.1 and 0.15 %, were considered as variable treatments. Data analysis showed that addition of WPC, significantly affected the physicohemical and sensory properties of the samples. Moreover guar and xathan gum affected all the physicochemical and sensory properties except for the after one and two days of storage, crust colour and taste. The results of this research showed that although WPC alone was not an appropriet substitution for egg white, the application of WPC at levels of 25 and 50% along with guar (0.3%) or xanthan gum (0.15%) could be an appropriate substitution for egg white while maintaining sensory properties and improving almost all of the physicohemical characteristices of muffin cakes.

Effect of ascorbic acid and alpha amylase on rheological properties and specific volume of strudel bread was examined. Enzyme in three levels (0,300, 500 ppm) and ascorbic acid in three levels (0,100,200ppm) were used. Strudel was storaged in -17.c for 7 days. The samples thawed and proofed (Relative humidity 70%, temperature 40.c, time 45min) and then baked and specific volume was measured by seed displacement method. Rheological properties of dough were measured by brabender farinograph and extensograph. Rheological results indicated that ascorbic acid increase the dough strength and extensibility of dough. In addition, enzyme and ascorbic acid increase specific volume of strudels. The best samples produced by 200 ppm ascorbic acid and 500 ppm enzyme in combination.

Honey is a plant extract that is gathered with bee and saved in comb after some modification. The apparent properties of honey, for example color, flavor and concentration, depend on rearing region of bee, climate and harvest season. The aim of this study was to investigate quality and adulteration in honeys that were presented in shiraz province. 96 samples of honey during 4 seasons (2007-2008) were collected. All the samples were evaluated by some tests such as diagnosis of artificial sugar, diastase activity, Hydroxy Methyl Furfural (HMF), determination of reducing sugars, saccharose, fructose to glucose ratio, pH, free acidity, moisture, ash, electrical conductivity, Suspended Solids (S.S) and deviation of polarized light. After statistical analysis of data, we concluded that in spring, summer, autumn and winter seasons, 25%, 37.5%, 16.7% and 48.53% of honey samples and totally %31.25 of whole samples of honey was recited is in a way of spurious. According to this results, it is proposed that using simple, fast, cheap and reliable laboratory methods for studying of adulterations in honeys that were presented (traditional and factorial packed) and following by related organization to prevent these instances.

This study has been done to survey of solvent system effect on extraction of grape seed extract and its antimicrobial properties. For this purpose, grape seed extracts were extracted with six different solvent systems. Minimum Bactericidal Concentration (MBC) of extract on six spoilage and Food-born pathogens was determined. The results indicated that MBC of different extracts have no significant difference and its value for Salmonella enteritidis, Escherichia coli, Enterobacter aerogenes was 1000 ppm. This value for S.aureus and listeria monocitogenes was 500 ppm. Results showed that gram positive bacteria were more sensitive than gram negative ones.