مجله علوم غذایی و تغذیه
سال سیزدهم شماره 1 (زمستان 1394)

In recent years، edible films and coatings have received much attention in food packaging. These packaging’s displays suitable film-formation properties such as their biodegradable and carrier of food additive such as antioxidant، antimicrobial، color and nutrients. The antioxidant activity (AA) of sage essential oil (EO) in various in vitro model systems was investigated. Physical and AA of Hydroxypropylmethylcellulose (HPMC) film with sage essential oil were also evaluated. In order to determine the AA of sag essential oil with DPPH radical scavenging، β-carotene/linoleic acid bleaching and reducing power assays، IC50 values were 907. 7، 454. 2 and 1362. 42 µg/ml respectively and sag essential oil showed lower AA as compared to BHT. Addition of essential oil to film led to 1. 5 times decrease in water vapor (WVP) and 1. 7 times decrease in oxygen permeability (OP). Films with essential oil have a lower transparency as compared to films without essential oil as lightness reduced from 95. 47 to 90. 3. The addition of essential oil resulted in a significantly decrease in tensile strength (3 times) and elastic modulus (2. 1 times) but elongation percentage haven’t significant difference (P>0. 05) with films without essential oil. Film with sage essential oil showed good protective effects against soyabean oil oxidation as peroxide value of the samples without HPMC film coating، packed by film and film with sag essential oil was 92. 7، 85. 9 and 66. 3 meq O2/kg oil respectively. The WVP and OP of HPMC edible film were improved by the addition of sage essential oil. Also، combination of essential oils into HPMC film is a suitable method for reducing of lipid oxidation.

Microbial transglutaminase (MTGase) enzyme is one of transferase enzymes that can catalyze the formation of ε-(δ glutamyl-)-lysine cross links in proteins via an acyl transfer reaction. The enzymatic cross linking of proteins by means of microbial transglutaminase strengthens protein-based food structures at the molecular level and positively affects properties such as serum holding capacity and gel firmness. In this study, the effect of using this enzyme (0.1, 0.2 and 0.3 g L-1), as a substitute for part of the skim milk powder, was evaluated.

The effect of enzyme on selected physicochemical (eg pH, titratable acidity, syneresis and viscosity) and organoleptic properties (texture, flavor, odor and overall acceptability) of spinach yoghurt was examined. Evaluations were performed at 0, 5, 10 and 15 days of storage at 4°C.

In general, addition of different concentrations of MTGase caused no significant changes in acidity and pH of yoghurt samples. However, it increased the viscosity and decreased the syneresis. It was indicated that the concentration of 0.1 g L-1 could be considered as the optimum concentration for MTGase. Although higher concentrations could produce better properties, but it was not economical, because fewer concentration of enzyme was able to create a sample similar to the control.

The results showed that the MTGase is an acceptable substitute for skim milk powder in spinach stirred yoghurt.

Pectin is a complex polysaccharide consisting mainly of esterified D-galacturonic acid residues in an alpha-(1-4) chain. The acid groups along the chain are largely esterifed with methoxy groups in the natural product. It has broad applications in both food and pharmaceutical industries where it acts as gelling and thickening agent. The present study was designed to determine the galacturonic acid content and degree of pectin esterification. In the current study Record cultivar of sunflower grown in Varamin region of Iran was selected for pectin extraction. The residue was dried in a drying chamber and stored at 4°C before use. The pectin was extracted by using 0.75% sodium hexameta phosphate at the pH of 3, 4 and 5 with the temperature of 75, 85 and 95°C for 20 and 40 minutes and the optimum conditions for the extraction of pectin, galacturonic acid content and the degree of esterification was studied. The highest yield was obtained at the pH of 5 and temperature of 95°C for 20 min. Galacturonic acid content or degree of purity related to the pectin was from 66.5% to 86%. Degree of esterification of extracted pectin was from 21% to 33% that clearly indicates the low methoxyl nature of the pectin. However, there were significant differences (p<0.05) between mentioned extraction condition factors, that is an important criterion for the quality of the pectin and the degree of esterification. It seems that the pectin extracted from sunflowers head show a high potential for commercial food applications.

During the past decades as well as in recent years, there has been an increase in the production of edible mushrooms in the world. Button mushroom (Agaricus bisporus) is the most popular edible mushroom having the largest production and consumption demand. Due to free exterior coating, shelf-life of these species of mushrooms is less than 3 to 4 days. The purpose of this study was to investigate the effect of chitosan-lemon essential oil on the shelf-life of whole button mushroom (Agaricus bisporus). The obtained lemon essential oil at the concentrations of 0.25% and 0.5% have been add to 0.25% and 0.5%chitosan solution. Mushrooms, either packed or unpacked were dipped into the solution and maintained in polyethylene containers at the temperatures of 4±1°C and 25±1°C. Weight loss (%), ascorbic acid concentration, respiration rate and colors of all the treatments were measured on the 3rd day. Lemonene is the most common monoterpene component in lemon essential oil. The chitosan-lemon essential oil coating had significant effect on the weight loss (%), ascorbic acid concentration, respiration rate and color changes over the time. Temperature and storage conditions had significant correlations with the mentioned factors. Increased concentration of chitosan- lemon essential oil is inversely related to the amount of weight loss (%) and respiration rate and it has a direct linear relationship with ascorbic acid retention. Based on the results of this study packed mushrooms with 0.5% chitosan and 0.5% lemon essential oil that was stored at 4±1°C showed superiority over the other conditions.

excessive use of artificial sweeteners along with increased body mass raises the risk of cardiovascular diseases, asthma, arthritis, type2 diabetes, stroke, high blood pressure and other diseases and leaves adverse metabolic effects. This study investigates the effect of fructose on obesity and its effects on biochemical parameters in adult male mice (NMRI).

Investigation was carried out in two stages. In the first stage of the treatment which lasted 8 weeks (n=6) the control group received water and rodent food, the obese group had a high-fat diet and the experimental group1received high-fat diet (1382 Kcal) along with 20% of fructose gavage.In the second stage of the treatment which lasted 12weeks, the control group 2, obese group 2 (received rodent food for the last four weeks) and experimental group 2 (received fructose with the same dosage for the last4 weeks) and the study continued for 12 week. The weights were measured every week and the amount of serum fructose and biochemical parameters were measured by sandwich Elisa method.

Obese and the experimental group1showed more weight gain as compared to the control 1 and statistically the results were significant (P≤0.001) but experimental 1 showed less weight as compared to the obese 1 but was not significant. Also the experimental group 2 showed higher weight gain as compared to control 2 which was statistically significant (P≤0.001). Fructose levels were higher in all the groups as compared to the control group. The same result was observed for glucose, total cholesterol, TG, LDL with the decrease of HDL.

The extra calorie intake is stored in the form of fat leading to weight gain and it is indicated that the receiving of 20% fructose does not play a strong role in gaining weight.

Ketchup is a heterogeneous suspension that is used as a condiment to improve the flavor and color of the food. During storage it changes color, losing consistency with the occurrence of syneresis. In this study the stabilising effect of salep and carboxy methyl cellulose (CMC) on the acidity, pH, color, syneresis, rheological characteristics, microstructure and sensory properties of the ketchup have been examined. In this research salep at the level of 0.18, 0.36, 0.45, 0.54, 0.72 and 0.9% with CMC were used in the formulation of ketchup. Color parameters, syneresis, the rheological characteristics, microstructure and sensory properties of the samples were evaluated after one day and thirty days of production. The samples containing 0.45% CMC and 0.45 to 0.22% salep after one day, and samples containing 0.45% CMC after thirty days of production had the least brightness. The samples with 0.9% salep had the maximum red intensity for both periods and samples containing 0.72% and 0.9% salep had the best color score after one day and thirty days of production, respectively. Syneresis in the samples were decreased by the addition of salep in both periods. CMC have a greater impact on the psuedoplastic behavior of ketchup and the highest viscosity was related to the samples containing 0.72% salep. By fitting the power law equation, sample containing 0.45% CMC showed stronger gel structure as compared to other samples containing salep. Microscopic images showed the sample containing 0.72% of salep had more compact and better texture than others. The scores given to the sensory properties were in acceptable range and there were no significant differences between the samples. Salep had a positive effect on the color of ketchup, reduced the syneresis and improved the viscosity. Although CMC had a greater impact on psuedoplastic behavior of ketchup, but microscopic images of the samples confirmed better and more compact structure for samples containing 0.72% salep.

Somesynthetic antioxidants namely BHA and BHT are used as food additives in order to improve the quality and shelf life of food. Although these antioxidants exhibit higher antioxidant activity as compared to the natural antioxidants such as ascorbic acid, but in relation to their safety and related aspects to health, there is a cause for concern. Therefore the use of natural antioxidants to replace the synthetic antioxidants is considered as an important aspect and research concerned with this matter has been regarded quite important. Peptides obtained from proteins hydrolysis are examples of natural antioxidants that have been discussed in recent researches. In this study protein hydrolysate was produced from soya protein isolate using Alcalase 2.4l and the effect of different hydrolysis conditions such as temperature, time and enzyme/substrate ratio, on degree of hydrolysis and antioxidant activity of the product were investigated in a completely randomized design and then the Fe++ chelating activity and reducing power of protein hydrolysate was evaluated. The highest degree of hydrolysis was observed at 55°C after 210 minutes with the enzyme/substrate ratio of 90 Anson unit/ Kg substrate that was 30.27 %. Under these conditions, the Fe++ chelating activity reached its maximum concentration, whereas the Fe+++ reducing power showed the absorption of 0.15 that indicated lower value as compared to the highest obtained reducing power. The protein hydrolysate obtained from soya can act as a natural antioxidant with a high nutritional value and other biological properties and in appropriate concentrations might act as the synthetic antioxidants.

A comparison has been made regarding the effect of conventional polyethylene packaging and nano silver based on titanium dioxide concerned with the fungal growth of bread consumed. This experimental study was conducted in order to increase the shelf life storage of the bread produced.

Twenty-four samples of 6 different types of bread loaf were randomly obtained from 12 bakeries in District 2 of Tehran. The samples were packaged with 3% and 5% nano coatings and also conventional polyethylene coatings as the control group. The bacterial examination of the samples were carried out twice on 1st, third, seventh, fourteenth and twenty eight days according to the national standards of Iran.

This study showed that the film type and storage period were the main factors that significantly influenced the fungal flora of bread (P = 0.000). With the presence of nano coatings fungal flora of bread decreased with an increase in the storage period. However this correlation was not similar in most of the breads examined and also the fungi types, therefore significant differences were observed (P = 0.000).

According to the results of the present study and regarding the growth population with respect to the improvement in the safety, nano-silver particles which are based on titanium dioxide are preferred over the polyethylene packages. Therefore using such packages are highly recommended in bakery industry after the safety assessment of nano-composite.

According to the nutritional investigations, date fruit (Phoenix dactylifera L.) has a good nutritional value and is potentially a strategic export product due to its widespread cultivation in Iran. Date fruit plays an important role in the diets of Iranian people. For these reasons, monitoring the quality and safety of date is necessary and essential. In this survey, 15 samples of different brands of sayer date fruit were collected through Ahvaz market in order to analyse the heavy metals namely Pb and Cd, as well as Fe, Cu and Zn and detect aflatoxins B and G and evaluate the microbial contaminations. Sample preparations of date fruit were carried out according to AOAC 999.11 (Pb, Cd, Fe, Cu and Zn), ISIRI 6872 (aflatoxins) and ISIRI 10899-1 (yeast and mold) standard methods. The mean values of Pb, Cd, Fe, Zn and Cu were 0.062, 0.040, 4.6, 1.5 and 2.5 µg g-1, respectively. There was no evidence to verify aflatoxins B and G existences in the collected samples. Microbial experiments have been performed on yeast and mold in date fruit samples. The results indicated no microbial contamination except in one sample suspicious to the presence of mold that was over the tolerable level according to ISIRI 16217. According to the results, the date fruit distributed in Ahvaz city was relatively healthy and safe to be consumed.

Hydrocolloids (gum) refers to series of polysaccharides and proteins that are dissolved or dispersed in water and increase the viscosity. The aim of this study is to investigate the effects of different drying methods on the rheological and textural properties of Balangu seed gum. Three different methods consisting of oven drying (40, 50, 60, 70 and 80°C), freeze drying and vacuum oven drying have been investigated. Rheological and textural properties of the solutions (0.55 and 3 %) were determined by a Brookfield rotational viscometer and texture analyzer respectively. The apparent viscosity of the solutions prepared from dried gum at different conditions and shear rate 60 s-1 varied from 0.056 to 0.203 Pa.s. By increasing the oven temperature from 40 to 80°C, the apparent viscosity of gums decreased from 0.161 to 0.056 (shear rate 60 s-1). The amounts of hardness, stickiness, consistency and adhesiveness of Balangu seed gum gel (3%) were changed from 33.1 to 46.9 g, 9.90 to 14.8 g, 245.3 to 487.8 g.s, and 64.1 to 130.8 g.s at different drying conditions respectively. The results indicated that freeze-dried gum exhibited the highest viscosity among all the dried gums and with increasing oven temperature the apparent viscosity of gums was decreased. The highest value of hardness and consistency of gum texture were related to the freeze-dried gum.