IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2005 | Volume:2 | Issue:2|Papers Count:12

In our country, bread is mainly baked from flours with high extraction rate and low fermentation time that it results in increasing of the phytic acid and its undegradation in bread making process. This reaction results in low absorption and bioavailability of minerals (specially Fe) and proteins in the body. Good conditions during fermentation of bread dough can have a significant effect on the lowering of phytic acid in the final product. In this study the effect of quantity and type of the leavening agents, fermentation time and temperature on phytic acid content of dough was investigated.Barbary dough was prepared using flours with 81% extraction rate. Afterwards the effect of different treatments such as; different leavening agents (dry yeast, fresh compressed yeast, sour dough and without leavening agents), 1.5, 2.5 and 3.5 (h) fermentation times, 25, 35, 45oC fermentation temperatures on phytic acid content of doughs were investigated. The results showed that 3% fresh compressed yeast, 2.5 (h) fermentation times and 25°C & 35°C temperature were the best treatments for decreasing the phytic acid content in the barbary dough.

In order to conduct impact loading test on agricultural materials, a frictionless instrumented pendulum was developed. The apparatus consists of a heavy anvil, with minimum vibration, a pendulum arm with impact weight, graduated plate (scale), a potentibmeter and an electronic data acquisition unit. Technical specifications and dimensions of the apparatus are suitable for testing of various agricultural commodities, including small grains, by impact loading. This apparatus can be utilized to determine: strain energy, kinetic energy to rupture, coefficient of restitution and specific energy. In order to investigate the capacity and technical specifications of the instrumented pendulum, single kernels of five wheat varieties at two levels of moisture content (6.5 and 15%), w.b) were tested. The pendulum was used successfully for rupture energy measurement and related parameters. According to the results, wheat moisture content had a significant effect in coefficient of restitution and strain energy. However, taking into account the grain dimensions (in the form of specific energy), its effect was reduced. The minimum kinetic energy required for causing failure in the dry and moist samples was determined to de 33 and 72 mJ, respectively. Results indicate that it is possible to distinguish wheat varieties based on strength properties extracted from pendulum impact loading test and that obtained data scatter is less than observed in static compression tests.

Microflora of agriculture's products is one of the important quality factors. Ten varieties of dates (Phoenix dactylifera) at three stage of edible maturation (kharak, rutab, tamr) were examined for total microbial count, yeast and molds in Khuzestan of Iran. In this study young (<I0 years) and old (>40 years) date palms were compared. Total counts, yeast and molds were high in kharak and increased sharply at rutab, then decreased at tamr. Microbial counts of kharak were higher than tamr. Total microbial, yeast and mold counts were the highest at rutab in all of the samples (p<0.001). Old of date palms did not significantly effect on microflora of date fruits (p<0.001). Aspergillus was detected only at kharak in two varieties and did not show in any samples. If condition of after harvesting is to be good, this product can export better.

Change in some quality characteristics of the kutum (Rutilus frisii kutum) was investigated. In this work, changes in moisture (M), total lipid (TL), peroxide value (PV), thiobarbitoric acid (TBA), free fatty acid (FFA), and heme iron (HI) and sensory evaluation (such as texture, general appearance, eye, color and odor of gills) were determined during 1, 4, 7, 10, 13 and 20 days after ice storage period. Statistical analysis showed significant decrease in all samples with regard to oxidative and hydrolitic deterioration (P<0.05). Also, sensory evaluation through indexes of eye, texture, general appearance, gill odor and gill appearance were recorded excellent to good till 4th and good to acceptable until 10th days.

Temperature history of unhulled pistachio is important because of its effects on shell staining. Shell staining causes pistachio nuts to have less commercial value. Laboratory tests showed that two factors (temperature and holding time) and their mutual effects have significant effects on the degree of pistachio's shell staining. The study on two Iranian pistachio varieties (Akbari and Kalleghochi) indicated that there is no significant difference between these two varieties in terms of shell staining. In addition, it was found that if nuts are kept at 40°C more than 24 hours, shell staining would be greatly increased. At 30°C the minimum holding time required for staining is 36 hours.The results also showed that in bulks of unhulled pistachio, which were stopped before processing, there was a high temperature in the core of the bulk because of improper ventilation, while the temperature in the baskets was about 3.5°C to 6.4°C under the ambient temperature. This study indicated that if any delay occurred in the processing, basket keeping of nuts will cause less temperature increasing and less poor quality. Therefore, the safe holding time of the product will be increased.

Moisture sorption isotherms are useful in food dehydration, storage and packaging. Due to the complex food composition, theoretical prediction of the isotherms is not possible and experimental measurements are necessary.Moisture sorption isotherms of black currant raisins were determined at 30, 40, 50, 60, 70 and 800C, using the standard static gravimetric method developed by the European cooperation project COST 90. GAB, Smith, Oswin, Halsey, Henderson and D'Arcy-Watt equation were fit the data. The experimental data were fitted well with GAB equation at 40, 50 and 800C, with Halsey equation at 30 and 600C and at 700C with D' Arcy- Watt equations. So, Isosteric heat of sorption data obtained at different moisture content.

In this study, the effect of different levels of powdered and granular forms of activated carbon on patulin reduction in apple juice has been investigated by HPLC, using factorial experiment based on completely randomized design. Results showed that powdered form on patulin reduction of apple juice was more effective than granular form. Patulin content was reduced significantly by increasing the level of powdered form, whereas patulin content was removed completely by using 5 g/l in all contact time levels (5, 15, and 30 min). Also patulin content has been decreased significantly by increasing the contact time with lower content of powdered form. The patulin content was reduced to 2.4 mg/l by using 3 g/l of powdered form with 30 min contact time which did not have statistically difference with complete diminishing of patulin. According to the acceptable level of patulin in apple juice (50 mg/l), 3 g/l of powdered form with 5 min contact time could reduced the patulin amount to lower than the acceptable level.

The effects of pH (4,4.5 and 5), inoculum level (102 and 104), temperature (5,15,25,35 and 45 0C)and type of the food (barley or mushroom soup) on lag phase of growth of Staphylococcus aureus in packet commercial Iranian soups (barley and mushroom) were evaluated as a factorial design study. The lag phase of growth of this bacteria was affected significantly (P<0.05) by the variables of "Temperature", "Inoculum" and 2-way interaction of "Inoculum x Temperature" but not by kind of soup used in this study. Regression equation was derived relating lag phase of growth to "Temperature", "Inoculum" and 2-way interaction of "Inoculum x Temperature". From this model the values of predicted tag phase of growth of Staphylococcus aureus can be calculated from any combination of the factors in this study (R2 = 0.952).