IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2012 | Volume:9 | Issue:36|Papers Count:15

In this study, Mazafati date samples were dried using a cabinet drier at five temperatures (50, 60, 70, 80 and 90 oC) and air flow rate of 1 m/s. Changes of total soluble solids, browning, pH, acidity and color parameters (L*, a* and b*) of date samples during drying were determined and compared. The results showed that total soluble solids, browning index and acidity increased and pH of date samples decreased.Moreover, L* and b* color parameters decreased and a* value increased. Overall, it was concluded that the moisture of Mazafati dates can be reduced by industrial drying. Furthermore, air temperatures of greater than 70 oC have negative effects on color of the date samples. Therefore, drying temperature of 70 oC was found to be the optimum condition for drying process of Mazafati date.

Pistachio kernel Akbari variety cultivated at damghan coated by whey protein based edible film incorporated with zataria multiflura essential oil. Minimum inhibition concentration and minimum lethal concentration of zataria multiflora essential oil against Aspergilus flavus were determined by inspection of mould growth inhibition on culture surface by direct method. Different concentrations 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 5000 and 5500 ppm of zataria multiflura essential oil were used in edible coating composition of pistachio kernel for measuring extension inhibition of inoculated disk growth including nine days mould culture in coated pistachio. Results shown that in essential oil concentrations lower than 4000 ppm, A. flavus grown in samples. With increasing essential oil concentration, inoculated mould growth reduced significantly. Afterward inhibition of above mentioned concentrations of zataria multiflura essential oil in pistachio kernel coated by whey protein based edible film incorporated with different concentrations on production aflatoxins B1, B2, G1 and G2 were analysed by high performance liquid chromatography (HPLC), results shown that concentrations higher than 4000ppm could inhibited aflatoxin production in pistachio kernel.

In this study carps slaughtered by exsanguination and hypothermia and post mortem flesh quality attributes in order to determine effects of pre mortem activity during slaughtering on fish flesh quality evaluated. Results showed different slaughtering methods significantly affected on flesh quality (P<0.05). Maximal rigor index was observed after 12 hours post mortem in hypothermia group, however rigor index reached maximum at 3 and 9 h post mortem for the asphyxia and exsanguination groups. In overall during experiment period flesh pH in hypothermia group was higher than other groups. Flesh pH in hypothermia, exsanguination and asphyxia was 6.53, 6.34 and 6.32 respectively.In this study refraction index ranged 1.36-4.84. Drip loss had significantly differences in experimental groups (P<0.05). Drip loss (%) in hypothermia, exsanguination and asphyxia groups 72 h post mortem was 1.73, 1.84 and 1.86 respectively. Flesh colorimetric analysis showed no significantly differences among experimental groups (P>0.05). Hypothermia, exsanguination and asphyxia slaughtering procedures significantly affected on colorimetric skin color parameters during time and in experimental groups (P<0.05). During trial period skin L*, b* and Hue* increased and skin a* decreased. Chroma* showed no considerable differences during trial. Results of this work showed slaughtering fish by hypothermia had higher flesh quality in comparison to other groups.

Plant essential oils are increasingly used as natural food preservatives. Understanding their chemical composition and their antimicrobial activity in the context of food health and safety seems indispensable.In the present study the chemical composition of essential oils of Mentha longifolia L. and Cuminum cyminumL., which were obtained using a Clevenger apparatus, was analyzed by GC/MS. The antimicrobial effect on growth of Bacillus cereus and Bacillus subtilis in different concentrations during 15 days incubation at 8 and 25 oC was done in commercial barley soup. The taste acceptability of these essential oils was also assessed. The result indicated pulegon with 31.54% and cuminaldehyde with 29.02% were the most compounds found in Mentha longifolia L. and Cuminum cyminum L., respectively.These essential oils at the 8 oC showed significant reduction of bacterial count. The lowest concentration of the essential oils inhibited bacterial growth compared to the controls. Essential oil of Mentha longifolia L. showed more antibacterial activity compared to Cuminum cyminum L. essential oil in similar concentrations. On the other hand, Bacillus cereus was more sensitive to these essential oils than Bacillus subtilis. A concentration of 0.15 mg ml-1 of these essential oils showed the maximum taste acceptability.This study clearly demonstrated that these essential oils could be used in some food systems without any undesirable palatability.

Ohmic heating has an advantage over conventional indirect heating methods because heater (electrode) surfaces temperatures are comparatively lower as heat is generated within bulk fluid. Conventional ohmic heating under typical low frequency alternating current (50 or 60 Hz) could cause hydrogen and oxygen evolution due to electrolysis of water. This process could develop the electrodes decay or corrosion. Any decay or corrosion of electrodes shorten the life time and contaminate the food. The main objective of this study was to investigate the rate of the electrodes corrosion in the ohmic heating process. For this purpose the concentrations of Fe, Cr, Ni, Mn, and Mo from the stainless steel electrode migrated into ohmic and conventionally treated soup were measured. In this study migration of the major key metal ions from stainless steel measured by Atomic Absorption. The results showed that overall ohmic treatment yielded the same migration residues of all metal ions, compared to the conventional retorting with similar electrodes. Concentrations of all metal ions migrated into food samples after ohmic treatment were far lower than dietary exposure levels so that this technique can ensure the safety and quality of food supplies.

The present work was undertaken with an objective to study the design, development and construction and performance evaluation of a batch ohmic heating system. Direct ohmic heating (Joule’s heating) is a technology to warm up the food using an electric energy where electric current is passed through a material which gets heated by virtue of its electrical resistance. In this study, firstly new batch ohmic heating containing a static cell (200-mm-long Teflon cylinder with 94 mm diameter at a constant voltage gradient of 15 V/cm) was developed and constructed. To evaluate the performance of this heating unit various food systems was used, i.e. sodium chloride solutions (concentrations: 0.2 and 0.6% w/v), starch solutions (2 and 5% w/v) and 0.5% w/v NaCl, a two-phase food systems (5% starch, 0.5% w/v NaCl and oil (1% and 10% w/v). Heating rates for previously named food systems were determined by tracking and recording the temperature profiles for a given time intervals. The data indicates the heating up rate increases with increasing concentrations of starch and salt but decreases with increasing oil in food.

In this research, the effects of three variables, soymilk concentration (0-25%), CaCl2 (0.3-1%) and coagulation temperature (30-40 oC) on textural properties of UF Feta cheese made from cow's milk and soymilk blend were investigated. Texture profile analysis (TPA) and penetration test were used to determine textural properties of products. At TPA test, hardness, cohesiveness, springiness, gumminess, chewiness and hardness 1 work done characteristics and at penetration test, hardness adhesiveness, adhesive force and hardness 1 work done characteristics were measured. The central composite experimental design (CCD) was used and the data were analyzed using response surface methodology (RSM). Coefficients of determination, R2, of fitted regression models for all characteristics were above 0.85. The Result of analysis of variance (ANOVA) table showed that lack of fit was not significant for all response surface models at 95%. Therefore, the models for all response variables were highly adequate. Also there was extra similarity between results obtained from TPA and penetration test for same traits. Therefore, when necessary we can replace these experiments by each other.

Barbari is one of the most common flat bread in Iran, with a relatively short shelf life. In this study different packaging material and gas composition inside the packaging were investigated in order to extension the shelf life of Barbari bread enriched with whole soy flour. Gas compositions of packages were selected as 70%CO2 and 30%N2, 50% CO2 and 50%N2 and normal air considered as control. Bread samples were packed into the different packaging i.e. oriented polypropylene (OPP) (33m) as the control, high-barrier laminated of Polyethylene terephthalate– Aluminum – Linear low-density polyethylene (PET–Al–LLDPE) (12-7-65), and vacuum bags PET-PET-LLDPE (12-12-65). Quality characteristics of bread samples were evaluated during 21 days of preservation in ambient condition (25±1 oC and 38±2% relative humidity). Microbial stability of bread, texture as staling rate index and organoleptic quality of the new products estimated periodically. In the treated and control samples increasing Co2 concentration caused increase in the both hardness and shelf life.Organoleptic test showed that, CO2 gas affected the bread taste with undesirable taste under MAP (modified atmosphere packaging) storage. 3 layers Packages contains aluminum due to high resistance to vapour demonstrated more effect on maintaining quality and softness of bread during time. Vacuum package and 3 layers Packages also prevents microbial bread spoilage by prevention of oxygen entering in packages.

The objective of this research was to produce fermented dairy beverage with Propionibacterium freudenreichii ssp. shermanii and study the microbiological characteristics immediately after fermentation and during cold storage. In this study, impact of two process variables of incubation temperature and inoculation ratio on microbiological characteristics was studied by full factorial design. For the preparation of the fermented dairy beverage, a mixed culture of Lactobacillus acidophilus and Propionibacterium freudenreichii ssp. shermanii was grown at the ratio of 1: 2, 1: 4 and 1: 8 and incubation was performed at 30, 35 and 40 oC until the pH reached 4±0.1. Cell count of L. acidophilus was conducted on MRS Agar and incubation at 37 oC. Enumeration of P. freudenreichii ssp. shermanii was done on sodium lactate agar (NaLa agar) medium and incubation at 30 oC. In the most suitable condition for propionic acid production, profile of viability of microorganisms was determined in intervals of 0, 7, 14, 21 and 28 days. Also, phase separation of produced beverage was studied during the first week of storage at 4 oC. The maximum viable cell count of P. freudenreichii ssp. shermanii was occurred by inoculation ratio of 1 to 4 and incubation temperature of 30 oC. There was an adverse and significant (P<0.05) relationship between viability of P. freudenreichii ssp. shermanii and incubation temperature. The maximum cell count of L. acidophilus was observed in a mixed culture of L. acidophilus and P. freudenreichii ssp. shermanii at ratio of 1 to 8 and incubation temperature of 35 oC. Considerable decreased cell counts of P. freudenreichii ssp. shermanii and L. acidophilus were obtained during the first and the last weeks of cold storage, respectively.

Malting process includes steeping, controlled germination that after kilning nutritional properties and crispy of product enhance. Adjuncts are used in the most countries for cost reduction purposes without any undesirable effect on final product. The purpose of this study was determination of changing length, width, thickness, kernel density, bulk density, porosity, total nitrogen, reducing sugar, diastatic activity, cold water extract, pH, ash and texture during malting, and also mashing extract of malt process by using unmalted barley (sahra cultivar) as adjuncts at the rations of 20, 40 and 50 % was evaluated. Results showed that width, thickness, diastatic activity, reducing sugar and cold water extract of the samples increased over the malting time, whereas kernel density, bulk density, total nitrogen and ash decreased.Scanning electron microscopic examination of barley was revealed digestion of cell walls and protein matrix of endosperm walls. Increasing rations of unmalted barley as adjunct in mashing decreased the diaststic power, color, soluble nitrogen. Using unmalted barley as compared to mash from malted barley (100%) showed that the ration of 20% was better than the other rations.

Edible coatings are thin layers that are on surface of food materials and they are such as protector.Films and edible coating which are prepared from natural polymers especially proteins are under consideration in recently years. Aim of this search, is possibility of production of edible film from chickpea protein isolated and determinate the effect of chickpea protein isolated concentration and plasticizer percent on some properties of edible film. So was considered with using from central composite design of chickpea protein isolated in concentrations 4 -10 g, and glycerol plasticizer in range of 40- 60% of weight of chickpea protein isolated in pH=9.5. In this study was considered physical and qualitative examination like water vapor permeability, film solubility, transparency of edible films. Results showed that percent of plasticizer in experiments had right effect on water vapor permeability; thus increasing of protein concentration was caused increasing of water vapor permeability measure at statistical surface (P<0.01). The increase of plasticizer concentration is caused solving of films and increase of protein isolated concentration is caused to decrease of transparency of edible films.

Soy flour contains large amount of proteins, so that it show variety of functional properties. In this paper functional property such as water and oil absorption, foaming properties, emulsification and solubility of heated and unheated soy flour was determined. The effect of pH and ionic strength on these functional properties was studied. Foaming and emulsifying properties and protein solubility depended on pH and its minimum was in isoelectric pH. Emulsifying properties in native and heated soy flour was increased with increasing ionic strength until 0.4 molar. Heating increased water and oil absorption but decreased foam capacity, emulsification and protein solubility.