مجله علوم غذایی و تغذیه
سال چهاردهم شماره 4 (پاییز 1396)

Xanthan gum shows pseudoplastic behavior in solutions, and has less ‘gummy’ mouth feel than Newtonian ones. Therefore, xanthan gum has major application in food industry as a thickening and suspending agent. Xanthan gum is a bacterial gum and the production process is largely affected by the culture medium compositions. The aim of this study was to optimize an economic industrial medium for maximum yield of xanthan gum.
Xanthan gum production by Xanthomonas campestris ATCC 1395 using different culture medium was carried out in a stirred bioreactor with controlled pH and dissolved oxygen. A fractional factorial design was applied to identify the effective factors on xanthan gum production. Central composite design and response surface methodology were used to evaluate the individual and interactive effects of four major significant variables (glucose, sucrose, yeast extracts and (NH4)2SO4) on biomass and xanthan gum production in submerged culture medium composition.
The results indicated that both carbon and nitrogen sources had strong positive effects on xanthan gum production, but the carbon source, especially glucose, was determined to be more significant factor than nitrogen source in growth cell and production of gum. theoptimum culture medium for producing xanthan gum was composed of 53.75 (g/L) glucose, 27.8 (g/L) sucrose, 7.8 yeast-extract (g/L) and 5.6 (NH4)2SO4 (g/L). After 36 hours under the optimized culture medium in 5-L bioreactor the xanthan gum yield reached about 12.26±0.44 g/L, which was found to be in good agreement with the predicated value (12.43 g/L).
The optimized culture medium studied here can be a good candidate to improve the yield and consequently be more cost-effective in the production of xanthan gum.

Today one of the problems concerned with the agriculture and food industries is the import of approximately 90% of edible oils. It is therefore important to identify the chemical nature of an oil particularly the fatty acid composition in order to select the best quality. The aim of the present work is to evaluate seven different varieties of Canola and select the most suitable.
Seven different varieties of canola were obtained from Institute of Seed Improvement, Karaj Station. The seeds were subjected to oil extraction by solvent followed by the chemical analyses of the extracted oils namely fatty acid composition, induction period determination, quantitative determinations of Copper and Iron, quantitative determination of nonsaponifiable matter and qualitative and quantitative determinations of sterols and tocopherols.
The amount of the extracted oils for all the varieties examined ranged from 33.0 to 46.2%. The nansaponifiable matter content accounted for 1.88 to 3.10% where sterols were the major fraction. Tocopherols namely γ and α tocopherols were present but there were quantitative variations concerned with sterols and tocopherols in all the varieties examined. Mono and Poly unsaturated fatty acids concentrations ranged between 59.40 to 66.02 and 25.59 to 31.21 respectively among the varieties examined.
All the varieties examined had significant differences concerned with the chemical analyses. Oleic acid was the major fatty acid and traces of erucic acid were present among the examined varieties. All the crude extracted oils had induction periods ranged between 8.75 to 12.32 hours at 110˚C that might be considered satisfactory considering the fatty acid composition.

Ultrafiltered (UF) Iranian white cheese has the highest per capita consumption in Iran. Optimizing the formulation of transglutaminase -treated ultrafiltered milk makes it possible to develop a low-fat UF cheese with desired textural and sensory properties. However, persistence of active transglutaminase in cross-linking the cheese proteins during storage may adversely affect the product quality before it reaches the consumer. Thus, the present study aimed to monitor the changes in rheological and sensory properties of transglutaminase –treated low-fat UF cheese during shelf-life.
A control full-fat (16% fat), a control low-fat (5.95% fat) and an enzyme-treated low-fat (5.95% fat, 0.56 U transglutaminase/g protein, 8.79% retentate replacement with whey protein concentrate) ultrafiltered cheese were produced and their physicochemical, rheological and sensory properties were studied after 3, 20, 40 and 60 days.
Throughout the storage period, the lowest hardness parameters (fracture stress and Young’s, storage and lost moduli) belonged to the control full-fat sample, followed by the enzyme-treated and the control low-fat cheese samples. Hardness indices increased continuously during storage for all the samples among which the enzyme-treated cheese showed the highest rate of firming. This in turn led to significant difference (P Transglutaminase treatment of ultrafiltered milk results increase in hardness and thus decrease in texture desirability of the resultant low-fat cheese during storage.

Benzoate and sorbate are used to prevent the growth of microorganisms and to increase the shelf life of the food in general. The purpose of this study was to detect benzoate and sorbate in some food products using Dispersive Liquid Liquid Microextraction and High Performance Liquid Chromatography as well as to determine the extent of accordance between sorbate and benzoate contents in different foodstuffs with the permitted standard level.
Eight types of food samples consisted of soft drinks (n 15), Ultra High Temperature (UHT) milk (n=15), ketchup sauce (n=15), yoghurt drink (n=15), fruit juice (n=15), tomato paste (n=15), cake (n=15) and bread (n=9) were analyzed based on Dispersive Liquid- Liquid Microextraction method. Optimum conditions were determined as follows: sample volume, 5ml; extraction solvent (chloroform) volume, 250μl; disperser solvent (acetone) volume, 1.2ml; NaCl amount, 0.75 g/5 ml at pH of 4.
Benzoic acid was detected in 107 (93.8%) of the samples ranged from less than 0.1 to 1520 μg/mL and sorbic acid in 60 (52.6%) of the samples ranged from 0.08 to 2305 μg/mL. Among all the food samples, soft drinks indicated the highest concentrations of benzoate (1520 μg/mL) and sorbate (2305 μg/mL). 74.1% and 24.9% of food samples examined contained upper level of benzoate and sorbate respectively than the permitted level of National standard. Among all the samples, soft drinks and yoghurt drink were found to have the highest concentrations in this respect.
In general, sorbate and benzoate contents of soft drink, yoghurt drink, fruit juice, UHT milk, tomato paste and ketchup sauce were exceeded the amounts defined by the national standard, while industrial breads and cake samples had lower concentrations of these preservatives.

Modeling might be considered as a relationship between different variables during drying of food products and mass transfer kinetics and moisture diffusivity coefficients can be used as useful tools for the optimal control of the process conditions that improve the quality of the final dried product. Kiwi fruit has favorable taste and aroma and has a high nutritional value. The aim of this research work is to investigate the effect of radiation on the characterization of Kiwi fruit.
In this study the effect of radiation lamp power at three levels of 200, 250 and 300 W, at 5, 10 and 15 cm distance from sample surface on mass transfer kinetics, moisture diffusion coefficients, density, color change, texture and rehydration of the Kiwi were investigated.
The results showed that the lamp power and the distance from the sample surface have significant effect on moisture loss kinetics and drying time. By increasing the infrared lamp power, the weight loss is increased (61.01 %) and by increasing the infrared lamp power from 200 to 300 W, the effective diffusivity coefficient has been increased from 6.25×10 10 m2/s to 13.8×10-10 m2/s. The color of the samples were analyzed by image processing technique and the average color changes (ΔE) for 200, 250 and 300 W were 14.02, 19.09 and 21.66, respectively. The average density and rehydration for dried samples were 743 kg/m3and 229.18 %, respectively.
The effect of infrared power on effective diffusivity coefficient of Kiwi was investigated and found that the effective diffusivity coefficient is increased by increasing the source of heat. The hardness of dried kiwi slices through infrared dryer was in the range of 9.55-11.08 N. In the Kiwi drying process modeling as compared with other models, Page model had the best match with the experimental results.

Canola seed is one of the most important oil seed with high ratio of oil and high nutritional value and is economically recommended for cultivation and oil extraction. Extraction with ultrasound waves as a nondestructive and novel method might be employed. Therefore the aim of this research is optimization of extraction of canola oil by ultrasound waves and RSM.
In this project, Response Surface Methodology was employed for optimization of canola oil extraction by ultrasound waves using hexane and hexane/isopropanol as solvents by the ratio of 3:2 (v/v). The influence of extraction temperature in the range of 35, 45 and 55℃, ultrasound treatment time for 30, 60 and 90 minutes and ratio of solvent to canola in three levels of 5, 10 and 15 ml/g were analyzed by Box-Behnken Design (BBD) based on extracted oil percent. The fatty acid compositions of the extracted oils using ultrasound-assisted method and soxhlet method employing gas liquid chromatography were determined and compared.
According to the high values of correlation coefficients of selected models optimized for hexane solvent extraction methods (R2 =0.93) and hexane-isopropanol solvent mixture (R2 =0.97) and no significant lack of fit tests (P>0.05) selected models might be useful to predict the extraction percentage of canola oil.
The results showed that the optimum conditions for canola oil extraction by hexane (22.39 %) and combined hexane/isopropanol (30.66 %) were respectively at ultrasound treatment times of 69.5 and 87 minutes, temperatures of 55 and 55 ℃ and ratio of solvent to canola of 6.39 and 9.12 (%v/w). Extraction efficiency was significantly improved by ultrasound as compared to the soxhlet extraction. Fatty acid compositions of the canola oils were not significantly affected by the application of ultrasound (P> 0.05). Therefore ultrasound might be regarded as a simple and rapid method to improve the extraction of oil without affecting the quality of the fatty acids present.

Oxidation occurrence in milk and dairy products causes rancidity that leads to changes in odour and taste, loss of nutritional quality and safety. The aim of this investigation is to assess the antioxidant efficiency of cumin seed and tarragon essential oils (EOs) at different concentrations in full-fat white cheese at 4°C over a 60-day period.
The components of the extracted essential oils were determined by gas chromatography equipped with mass spectroscopy. In order to evaluate the antioxidant activity of EOs in cheese, peroxide and tiobarbituric acid values were measured as means to evaluate the extent of oxidation during 60 days of storage.
The main compounds present in cumin EO consisted of cumin aldehyde, α- terpinene-7-ol and γ-terpinene and the main compounds present in tarragon EO consisted of estragol, β-cis-Ocimene and β-trans-ocimene. Two percent concentration of essential oils of cumin and tarragon exhibited the best antioxidant activity during 60 days of storage. There were not significant differences between the peroxide and tiobarbituric acid values of the samples treated with 1% and 2% of cumin EO on the 60th day of storage. Final peroxide and tiobarbituric acid values of the samples containing 2% cumin and tarragon EOs were 0.19 meq O2/kg, 0.07 mg MDA/kg and 0.16 meq O2/kg, 0.03 mg MDA/kg, respectively. Significant differences were observed as compared to the control sample.
It was concluded that tarragon EO was more effective than cumin EO in order to protect the oil against oxidation and cumin EO at the concentration of 1%, obtained the highest overall score concerning the organoleptic acceptance.

Vacuum frying is a new technology that might be useful for producing new kind of snacks such as fruit and vegetable chips. The reason for this technology is to reduce the presence of oxygen and lower the processing temperature. The aim of this work is to determine the effect of process parameters namely time, pressure, temperature on the specific characteristics of green bean in order to achieve the optimal processing condition.
In this research, samples were processed in predetermined temperatures, pressures and times by using statistical response procedures. The effects of frying time and temperature and pressure on reduction of moisture, oil absorption, shrinkage, texture, and color were studied.
The optimum conditions of 119.13oC for the temperature, 285 mbar for the pressure and 14.63 min for the time were obtained. The results showed that the time of the exposure to frying has a direct and significant relation to vacuum pressure and the samples moisture level is related to frying time and the moisture of the sample is significantly reduced (pThe results indicated that vacuum frying can improve the nutritional quality of
the food with reduced cost and avoid the loss and wastage of the product.

Casein-based edible films due to high nutritional value have potential to protect the food products. The purpose of this investigation is to prepare sodium caseinate film containing Lactobacillus acidophilus and Lactobacillus casei and determine the antibacterial activity of the film against Listeria monocytogenes inoculated into the silver carp fillet.
In this survey, Lactobacillus acidophilus and Lactobacillus casei bacteria in the form of solution were added to sodium caseinate film and dried at 40°C for 24 hours. The effect of the film to control Listeria monocytogenes was determined on silver carp fillets and culture media during 9 days at 96 hour intervals. The viability of the LAB bacteria within 12 days in culture medium and fish fillet were studied at 96 hours intervals. The effects of incorporated bacteria on the physical and mechanical properties of the film were also examined.
The viability of lactic acid bacteria in fillets was increased. Both bacteria caused reduction in the Listeria count as compared to the control group. Lactic acid bacteria had a significant effect on the solubility percentage, moisture, L index and color difference, however there were not significant differences in tensile strength and elongation percentage.
Due to a significant decrease in L. monocytogenes viable count on culture media, it seems that the incorporation of LAB cells into films could be a useful method to control food pathogens.

The oxidation process in oils and fats and the speed of oxidation to some extent depends on the presence of prooxidants namely metals. The application of chelatingagents namely citric acid among others can retard this process. In this study the chelating effect of tea extract, tannic acid and citric acid are evaluated and compared to each other.
Copper in the organic form at the concentration of 0.1 ppm were added to tallow, sunflower seed, canola and olive oils and then by the addition of 0.01% citric acid, 0.01% tannic acid and 0.1% tea extract the effect of chelation concerned with each oil has been evaluated.
The results indicated that all the chemicals (citric and tannic acids) and tea extract added have chelating effect on copper and increased the induction period of the oils concerned.
It was concluded that tannic acid followed by tea extract and citric acid had the best chelating effect on copper.