IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2009 | Volume:6 | Issue:3|Papers Count:15

Starch is the most abundant carbohydrate biopolymer that has excellent film-forming properties. But poor resistance to water vapour transport and poor mechanical properties are of its main problems. In this study a series of corn starch films with varying concentrations (0–20 %W/W) of citric acid and carboxymethyl cellulose (CMC) were prepared by casting method at 60°C. The effects of citric acid on water vapor permeability (WVP), moisture absorption, solubility and mechanical properties were investigated. The WVP decreased from 4.63 to 2.61×10-7 g/m.h.Pa as the citric acid percentage increased from 0 to 10%W/W. When the citric acid content of the films reached to 20%W/W, WVP increased about 15%. Moisture absorption and mechanical properties exhibited similar trends. In the presence of 10% citric acid, the introduction of CMC improved the moisture resistance of the composites. Using of 20%W/W CMC in the formulation increased ultimate tensile strength (UTS) by more than 59% compared to neat starch film. However, by increasing of the CMC concentration, the strain to break (SB) did not reduce significantly.

According to increasing trend of the consumption of ready to use leafy vegetables, mainly impact of freezing on sensory attributes of the vegetables and necessity of determination of the best conditions for frozen storage of leafy vegetables, this research carried out for determination of the best frozen storage time and temperature of Allium ampeloprasum, Lepidium sativum and Stureia hortensis mixtures.This study was done at first for storage of ready to use and comminuted leafy vegetables entitled Ghormeh Sabzi mixture in -9, -12 and -18°C as well as 120, 150 and 180 days by explorer method. At second for frying of vegetables of Ghormeh Sabzi and comparison of sensory attributes of freezed vegetables at each month by experimental method. Sensory attributes all treatments containing color, taste and acceptability were evaluated and compared statistically. The results of freezing temperature in 3 times indicate that color in -18°C is the first rank (P£0.05). Flavour has the first rank in -18°C in 120 and 150 days but flavour in 180 days in -12°C is the first rank without significant difference with -9°C and -18°C. Furthermore, acceptability in -18°C in 3 times is the first rank. The results of freezing time during 3 temperatures indicate that color, flavour and acceptability are not significantly different.The research results indicate that sensory attributes of the vegetables during 180 days frozen storage is affected by freezing temperature mainly rather than freezing time.

The high molecular weight polymeric fraction of gluten, glutenin macro-polymer (GMP) shows strong relation with breadmaking quality of wheat. In this study, GMP was extracted from different Iranian wheat cultivars with different breadmaking performances. The correlation was investigated between the wet weight and (small-strain deformation) rheological characteristic of GMP-gel with bread quality (loaf volume and height). The results showed a significant relation between gel amount and bread loaf volume and height. However, no positive and significant correlation was found between small-strain deformation rheological characteristics (storage modulus and tan delta) with breadmaking characteristics. Concluding, despite to GMP wet weight which is accepted as a predictive measure for breadmaking quality, small-strain deformation rheological analysis of GMP-gel can not be used for screening breadmaking quality between wheat cultivars.

The effect of flour hydration on the rheological characteristics of bread dough was investigated. For this purpose, hydrated zero-developed (zero mechanical energy developed; ZD) doughs, which hydrated out side of the mixer were used. The influence of hydration temperature (5 and 25°C) and time (1.5, 4 and 24 h) on hydration ability of doughs was investigated. Farinograph and Extensigraph experiments were used to study the behavior of hydrated doughs upon different hydration treatments. Results indicated that increasing hydration time and temperature led to an increase in hydration performance, thus hydration phase in Farinograms was decreased and finally disappeared. Comparing doughs prepared from ZD doughs versus those mixed from conventional flour-water mixtures showed that reduction in hydration phase (arrival time) in ZD doughs, especially upon hydration at 25°C for 24 h, arrival time was totally disappeared. However, doughs prepared with ZD-dough had lower Farinograph "stability" and higher "degree of softening" values compared to those mixed from flourwater mixtures. Only hydration at 25°C for 24 h gave suitable doughs for Extensigraph experiments. Evaluation of Extensigram of such dough compared with doughs mixed from flour-water mixer showed better rheological performance (higher Rmax , energy to extension and Ratio values).

The purpose of this work was to determine the effect of roasting temperatures and additives application on pistachio oil quality during the storage. The chemical and sensory analysis were performed on samples of roasted pistachio nuts only with salt (F1), without any additive (F2), with salt plus 1% ascorbic acid (F3), with salt plus 2% ascorbic acid (F4), with salt plus 1% sodium metabisulfite (F5) and with salt plus 2% sodium metabisulfite (F6). All samples were roasted at three temperatures (90, 120 and 150 C). The chemical analysis includes measurement of peroxide value, thiobarbitoric acid value (TBA) and free fatty acid (FFA), and also the sensory analysis includes rancidity and total acceptance were performed during 3 month of storage. Free fatty acid (%), peroxide and thiobarbitoric acid values as well as rancidity increased across the storage time for all treatments. Addition of ascorbic acid as an antioxidant, did not affect the total acceptance of the product but provided protection against lipid oxidation during the storage. Furthermore, using sodium metabisulfite prevented samples from oil deterioration being a little less efficient compared with ascorbic acid. During the storage, the pistachio nuts only with salt and without any additives (F1 and F2), had more FFA (%), peroxide and TBA values, and less total acceptance than other formulations. In addition, using of high temperature of roasting led to less quality of pistachio oil and decreased the total acceptance.

In this research, microbial, recombinant and animal rennet were used in the production of Iranian white cheese. The produced cheeses were compared regarding the yields of product, the rates of the proteolysis index, chemical, textural and some sensory properties during ripening period. The results indicated that there were significant differences in total solid content, salt and pH values of cheese samples (P< 0.05). The highest and lowest yields of cheeses were obtained with animal and microbial rennet, respectively. The proteolysis rates were significantly different with three produced cheese samples (P< 0.05). It was significantly higher with microbial cheese than with other samples. The hardness of cheeses produced using animal and microbial rennet were respectively maximal and minimal at the end of the ripening period. The observations of protein network arrangement also showed that the protein content of matrix has been decreased during the repining period. The maximal and minimal decrements were belonged to the cheeses produced by microbial and animal rennet, respectively. The highest and lowest sensory scores were obtained with control sample (animal rennet-based cheese) and microbial rennet-based cheese. According to this research, the cheese produced by microbial rennet showed lower quality compared to the animal and recombinant rennet. In general, because of the low availability of animal rennet and low quality of the cheese produced by microbial rennet, it seems that the recombinant rennet can be used as a proper substitute in cheese production industry.

Washing operation with different dilutions of salt water (3, 2, 1, 0.3) at different times (5,10 and 15 minutes) was used to reduce fishery odor from Silver and Big head carp fish pastes. Results showed that elimination of fishery odor increased while extraction of soluble proteins with salt water increased. Sensory analysis was used to determine the best formulae of 50,60 and 70 percent fish meat from the best eliminated fishery odor sample that sample with 70 percent fish meat selected as the best formulae. For determination of quality changes at -18°C, 2 variable level of BHA antioxidant (0.01 and 0.02 percent) with a blank sample (without antioxidant) were prepared. Results showed that total count of bacteria reduced and reached to 0 after 60 days while TVN and peroxide factors increased in each sample during storage time. So both peroxide and TVN tests could used for determination of storage time.

A structural study of traditional Iranian breads, in relation with staling has been carried out in this research by Scanning Electron Microscopy (SEM) employment. Popular Iranian flat breads of Barbari, Lavash an sangak were selected and stored up for durations of 24, 48 and 72 hours. During these time intervals, staling phenomenon occurred but the rate was varied among different bread kinds. It is evident that staling progress with time lapse, but it is different for 24, 48 and 72 hours of storage times. Microscopic study showed a quicker process of staling in Barbari bread during the first 24 hours of storage. Sensory evaluation was done for all the samples in respective time intervals. Results indicated no significant differences among panel judgements while there existed significant structural differences among bread samples. All samples became staled as compared with control, but Barbari bread became staler as compared with Lavash and Sangak. Overall results reveal that retrogradation of starch granules occurs during storage of bread, particularly at time lapses of 48 and 72 hours. Staling phenomenon occurred in all breads while its rates were different. In addition, it was shown that coagulation of gluten network during baking and its intensity during storage was an important factor. Flour components, baking conditions, time and baking process were also important interventing factors.

Consumption of meat products such as Patti is increasing specially in big cities, so safety and quality of theses products are very important. With consideration of meat price and possibility of substitution cheap kind meat, In this study 288 industrial and 96 hand made Patties marketed in Tehran tested for determination the kind of content meat by sandwich Elisa method .Results of this study demonstrated that in analyzed samples there was not swine and equine meat, but 43/8 percent of samples were not complying with production license formula and label claim for kind of content meat.

The effect of three hydrocolloids with different chemical structure and from different sources on the rheological properties of wheat flour dough, fresh baguette bread quality and its influence on bread staling were studied. The influence of the selected hydrocolloids (Guar, Pectin and Xanthan gum) on rheological behavior of dough was tested by using extensograph and farinograph. Rheological characteristics of wheat flour doughs were modified to different extent by hydrocolloids of varying chemical structure. The greatest effects, but not the better ones, at dough level were promoted by xanthan followed by guar, these hydrocolloids strengthen the wheat flour dough. Hardness and sensory characteristics of bread after storing for 24 and 48 h. Hydrocolloids affected in different extent to stored bread. Although different improvements were observed associated to specific hydrocolloid, guar was the hydrocolloid with an improvement effect on all the parameters tested, specific volume index and crumb hardness. In addition, during storage, guar gum showed an anti staling effect, reducing the crumb hardening.

The chemical composition, sensory attributes and acetaldehyde content of yoghurts produced from ultrafiltered milk retentates and normal yoghurt made with SMP were studied and compared. UF yoghurts had more content of acetaldehyde, protein, lactic acid and total solid than control but lactose content and syneresis were at lower level. The amount of produced acetaldehyde was dependent to the protein amount and by increasing the latter the acetaldehyde got higher. The quantity of acetaldehyde decreased during the storage of yoghurt. Scores for sensory analysis of UF yoghurts were higher than control. Yoghurt made from UF retentate with 13.5 % TS and 5.3% protein got the highest rating for all sensory properties and was comparable with one of the most acceptable yoghurts produced in Iran.

The aim of this research was to compare the benefits of wheat enrichment in the farm with flour fortification in the factories. Three experiments have been carried out in the early of third Millennium in 6 different provinces, i.e. East and West Azerbaijan, Kerman, Sistan and Balouchestan and Southern Khorasan. The first and second experiments (2000-02 and 2002-04), were designed based on t-distribution and included two treatments: The control plots were given nutrients based on Farmer's conventional fertilization practice (NP) and the treated plots received nutrients based on soil tests (balanced fertilization) in Meyaneh (3 wheat farms) and Naghadeh (1 wheat farm) in East and West Azerbaijan provinces. In the wheat fields, micronutrient-fertilizer solution with 0.5% was sprayed at three stages (stem elongation, heading, and a week after flowering). After harvesting, the grain yield, phytic acid, Zn and PA/Zn molar ratio were measured. Then, whole-wheat bead and regular bread prepared from these farms were fed for 4 and 6-month periods to different groups in Tajark, Khanghah and Kahriz villages in East and West Azerbaijan, respectively. Before and after feeding the village inhabitants, zinc (Zn) and iron (Fe) concentration were measured in their blood serum. In the third experiments, in the summer of 2003, a study on the effect of fortification and improvement of the quality of bread on the health of consumer subjects was carried out on the total personnel of Moghadam Mersad Military Station. A number of the drafted military service personnel of Moghadam Mersad Military Station and some personnel from Ravar Aboozar Military Station were selected for blood tests. During a 4-month test period, bread consumed at the Station and the associated units was fortified and the correct procedure of baking was taught to the bakers. The amount of Zn and Fe in the blood serum of the subjects was determined with an atomic absorption spectrometer. Fortification of the wheat flour was carried out at the Baghin Martyrs Station, by adding, 80 mg Zn; 50 mg Fe; 10 mg vitamin B1; 2.5 mg Vitamin B2; and 5 mg vitamin B6 per kg of flour. In the first and second experiments, the results demonstrated that there was a significant difference at one percent level for grain yield (a=0.01). Also, the statistical analysis revealed a significant difference for phytic acid, Zn and molar ratio of phytic acid to Zn (PA/Zn) in all wheat farms. Consumption of whole wheat bread in comparison with white bread for 4 and 6-month periods noticeably increased Zn and Fe concentration in blood serum especially in 6-month period. While the average Zn and Fe concentration in the blood serum in the second experiment for the control was 80 and 100, they were increased to 110 and 130 mg/deciliters after the intervention in Kahriz village. In the third experiment, in places where bread was not fortified, the average level of Zn in the blood serum of individuals was measured to be 72 mg/deciliters; whereas, the serum Zn of the test subjects consuming fortified bread for a three-month period averaged 89 mg/deciliters (P<0.01). For persons who fed on unfortified bread, 47% suffered from Zn deficiency but those who used the superior quality, fortified bread, only 10% suffered from this deficiency (P<0.01). While the number of people using stomach-problem-related medicines at the Beghin Martyrs Station during a 4-month period before the experiment was figured to be 1615, it was reduced to 1375 cases after the test; or a 15% decrease during a 4-month period. In conclusion it can be mention that superiority of the enrichment in the farm over flour fortification in the factory has been proven. Enrichment is preferred to flour fortification and its most important benefits are at least 20% increase in wheat yield as well as grain quality and more than 10% increase in minerals concentration due to more uptake by human's digestion system.