IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2006 | Volume:3 | Issue:3|Papers Count:10

Electrical conductivity (EC) is the ability to conduct electricity which is expressed as micro Siemens per centimeter (ms/cm). The conductance of the milk is attributed mainly to its salts content especially Na, K and Cl ions. Since measuring the milk’s EC is a rapid and inexpensive method for determining of the milk quality, therefore correlation between EC with pH, acidity, and total microbial count (TC) in raw milk was studied in order to assess the freshness of milk in this research. In a pilot study, using skim milk, pH, acidity, and TC were changed and EC measured at 25oc. Then a total of 200 samples of whole milk were obtained from the receiving platform of a dairy plant in Tehran. In one trial 100 samples of whole milk were examined for pH, acidity and TC. Also EC was measured in different temperatures of milk samples at the time of the analysis. In the second 100 samples of whole milk, pH, acidity and TC determined and EC measured at 25oC. According to the results obtained from the pilot study (with 10 repetition), increasing the pH caused a decrease in EC and vice versa (P<0.01). There was no significant correlation between EC and TC (P>0.05). No significant correlation was found between EC with pH, acidity and TC in other trials (P>0.05). It seems many factors may affect the EC in raw whole milk. Therefore measuring EC solely cannot determine the milk quality.

Saffron is one of the important agricultural products in Iran and has got importance in the Iranian agricultural export products. Iranian saffron dries under uncontrolled condition, as a result it’s got low quality. The aim of this study was to determine the effects of the three different ways of dehydration: Solar, Vacuum and Traditional on the qualitative characteristics of the saffron. The samples were picked randomly from the saffron farm on the Qayan city, The stigma's separated from the flowers and the chemical tests were done on the fresh stigma's and samples dried under controlled conditions(vacuum, solar) and then they were compared with the traditionally dried one's. Quality attributes of dried samples were determined by chemical, microbial and sensory tests and compared with traditionally dried samples. Results of the chemical test indicated that, the amount of the crocine was high in solar, vacuum oven dried samples, in compare with traditionally dried samples (shade & R.T): the Safranal measured by HPLC method was the same in dried samples in three methods. The results of the sensory tests on color, aroma and texture showed that, the color in dried state was desirable in vacuum and solar dried than traditionally dried samples, color in liquid state, (vacuum dried, solar dried samples) had desirable quality. The microbial tests on samples, indicating that, the solar and vacuum dried samples were in standard levels but traditional dried samples were not in the standard level. In conclusion, if we consider the quality parameters (color, aroma, texture and microbial status of dried saffron), the quality of the solar and vacuum dried samples was high to campare with the traditionally dried samples. As a result the solar and vacuum methods of dehydration can be applicable for saffron preservation.

One of the most effective surfactants, which is increasingly used to retard the staling of bread, is Sodium stearoyl lactylate (SSL). This research was carried out to assess the staling of flat bread containing different levels of SSL with different methods. Therefore, Taftoon bread was baked from dough containing 0.25, 0.50, and 0.75% SSL with standard method, sensory and staling evaluations were done on days 1, 2 and 3 by means of 5 trained panels of referees. Moisture content of the breads was determined in the same days with standard method. The texture of breads was evaluated by tensile, compression and shear tests on days 1, 2, 3 and 4 with Instron. Trained panel of referees could not find any significant difference between the sensory characteristics of breads but showed that chewing ability of the bread containing 0.50% SSL was improved from 5.5 to 6.1. Results of texture measurement showed that the force required to compress, shear, and tensile breads was reduced in breads containing SSL With regard to the results of the other tests; we could reveal that compression test was not suitable for Taftoon bread, which is flat bread and has a low thickness. Moisture of the breads did not change significantly on the tested days. The scores of staling were reduced, although most of them were not significant and this decrease was from 3.4 to 1.8 for the standard and from 3.6 to 2 for the bread containing 0.25% SSL and from 2.4 to 2.6 for the bread containing 0.50% SSL and from 3.7 to 2.4 for the bread containing 0.75 %SSL.Therefore we could conclude that by using sensory evaluation and texture analysis together, we could assess the bread staling.

The main objective in sugar industry is to remove the colorants and other non-sucrose compounds in order to obtain thin sugar juice with high purity and quality. The aim of this research was to study the potential of ultrafiltration process and its operational conditions (process time, transmembrane pressure & temperature) on improving the purification and de-colorization performance of thin sugar beet juice. Experimental data was obtained using the pilot plant UF membrane system equipped to a spiral wound module and a polysulfone amide membrane with MWCO 20kD. In this work, the effect of transmembrane pressure (at levels of 1, 2 & 3 bar), process temperature (at levels of 30, 40 & 50oC) and operation time (at levels of 15, 30 and 45 minutes) on the purification indexes in sugar industry (Brix, polarization, purity, hardness & color) has been investigated. The results showed that the increase of duration of UF process decrease the separation degree of CaO content and turbidity, whereas the purity ratio and color removal increased for the same condition. It was found that increasing process temperature led to decrease the separation degree of CaO content, turbidity and color removal, however the purity ratio increased in this case. Increasing transmembrane pressure also improved the separation performance of non-sucrose compounds for all the UF conditions studied. The trials displayed satisfactory separation with an average purity rise of 0.72 unit, 7.2% lower CaO content, 72.5% lower turbidity and 12.62% lower color in the permeate.

In this investigation, a number of canned Killka with oil and brine filling media were produced to survey the impact of filling media type on canned common Killka quality by traditional Mediterranean method. Qualitative characteristics including moisture, total lipid, free fatty acids, peroxide, tiobarbituric acid, fluorescence compound in aquatic phase of lipid extract obtained from fish and canned fish, and the fluorescence compound existed in filling media were determined. Results showed that hydrolytic rancidity product and the filling media fluorescence compound in brine canned was higher than the oil canned. The primary and secondary lipid oxidation indices (tiobarbituric acid and peroxide) had no ideal efficiency to evaluate the loss of quality due to the filling media type, while the fluorescence index had perfectly showed the quality loss. With regard to present interactions between fish tissue and filling media, it’s recommended determine the amount of filling media fluorescence compound as a good technique for quality assessment.

Purslane (Portulaca oleracea L.) is an annual, summer crop and belongs to Portulacaceae family. Although it is grow as a weed plant in field, but it is cultivated in wide range in south part of Iran. Pursalne is important in respect to unsaturated fatty acids and high nutritive value. For determining fatty acids, oxalic acid and mineral elements (K, Mg, Ca, Fe) of Iranian purslane cultivars, this research was carried out. Cultivars "Behbahan, Ahwaz, Borazjan and Tehran" were planted in greenhouse. Determination of fatty acids by gas chromatography showed that linolenic acid (omega-3) of leaf and seed were 19.69-30.15% and 19.42-29.81%, respectively. Oxalic acid content of leaf cultivars was over the range 40-80 g per 100 g fresh weight and the lowest amount was determined in cv."Borazjan". Dry matter content of leaf varied from 4.25 to 4.71%. Cultivar "Borazjan" had the highest potassium and calcium and iron content of cv. "Behbahan" was higher than other cultivars. Among mineral elements, magnesium content of cv. "Tehran" was 84.78 mg per 100 g fresh weight. Mean of potassium, magnesium, calcium and iron of Iranian purslane was 500, 66, 154 and 31 mg per 100 fresh weights, respectively. This research showed that Iranian purslane cultivars are rich sourse of omega-3 fatty acid, mineral elements and have lower oxalic acid content and recommended for human nutrition.

In this study macaroni was enriched at three levels with thiamine, riboflavin, niacin, and iron (as NaFeEDTA, 3H2O and SO4Fe,7H2O) in the range of 4.4-11, 2.64-4.8, 35.2-75, and 28.6-88mg/kg flour respectively. The influence of drying and cooking on the retention of these micronutrients were determined by HPLC. However, same effects on organoleptic characteristics of the samples were also evaluated by thirty in-house panelists.After drying, retention of vitamins, B1, B2 and niacin, were 86.1- 87.32%, 52.54-63.92% and 58.14-76.39% and after cooking were 67.79-73.72%, 71.5-79.08% and 62.80-70.17% respectively. No significant difference was observed in organoleptic characteristics of enriched samples, but the differences between each enriched sample and reference sample were significant (a£0.05).Regarding to the results of the research, enrichment of macaroni with 11mg thiamine, 4.8mg riboflavin, 75mg niacin and 28.6mg iron (SO4Fe, 7H2O) per Kg of flour weight, is recommended.

In this research stabilization and clarification of pomegranate juice were studied. This juice was analyzed and its effective constitutes in this process were determined and important factors in after haze production were evaluated. Pectinas enzyme was used for pectin elimination and optimized consumption amount, temperature and time were obtained as 110PPM, 50C, 60min. respectively. Clarifying materials such as Gelatin (70 g/ton), Kieselsol 15 % (250ml/ton) and Bentonite (250g/ton) were used and in each case optimum condition and their advantages have studied. Our work has shown that carbon active is not acceptable for pomegranate juice clarification. The process has the best result in low temperature (20C). Also, for the first time PVPP (polyvinylpolypyrrolidone) was applied to solve secondary hazes problems and to produce stable clarified juice whose satisfying results have reported. Its consumption amount was determined as 80g/100 lit.