فصلنامه پژوهش های صنایع غذایی
سال بیست و یکم شماره 1 (بهار 1390)

The effect of the addition of freeze-dried sourdough containing Lactobacillus plantarum ATCC 1058 and Lactobacillus reuteri ATCC 1655 on loaf physical and sensory characteristics as well as the shelf life of bread was investigated. Freeze-dried sourdough caused a decrease in pH and an increase in total titrable acidity of dough and the resulting bread. However, the physical properties of the bread (volume, height) were not changed. The moisture content of the control bread was significantly higher than that of sourdough added samples. The least moisture content (25.66%) was reported in freeze-dried sourdough bread containing Lactobacillus reuteri. Sensory characteristics of all breads were negatively influenced during bread storage. Maximum sensory was obtained for control bread followed by sourdough bread containing Lactobacillus reuteri. The addition of dried sourdough increased the shelf life of the bread. The starter Lactobacillus reuteri inhibited mold growth and extended the shelf life of the bread to 10 days compared to that of control bread (4 days).

In this study the antioxidant properties and total phenolics content of methanol (80%), acetone and water extracts of olive leaves produced by maceration method were examined. Two varieties of olive including Koroneiki and Roghani were studied. Various experimental models including reducing power, total antioxidant capacity and DPPH radical scavenging activity were used for evaluation of antioxidant activity of extracts and compared with synthetic antioxidants (BHA and BHT). At the next stage, effect of methanol extract of Koroneiki on oxidative stability of sunflower were assessed using peroxide value and thiobarbitoric acid index. Results revealed that the highest phenolic content (196.6±0.33 mg TAE/g extract) and the lowest IC50 in DPPH (106.065±0.55 µg/ml), reducing power (258.137±0.16 µg/ml) and total antioxidant capacity (205.9±0.18 µg/ml) indices were related to the methanol extract of Cronaiky. Also, methanolic extract of Cronaiky at 1000 ppm could control peroxide value and thiobarbitoric acid index and could be used instead of BHA and BHT at 100 and 200 ppm levels.

Milk thistle plant (Silybum marianum) is one of the medicinal plants which possess important nutritional and medicinal applications. It is shown that extracts of its leaf and the oil extracted from its seeds can retard liver diseases; and promote antioxidant and anticancer effects. In this research, physicochemical properties and fatty acid composition of extracted oil from milk thistle seeds were studied. The total oil content of the seeds was 28.9% and physicochemical properties were as follow: refractive index 1.452, chlorophyll content 0.55 mg pheophytin/kg oil, acid value 0.25 mg NaOH/g Oil, peroxide value 0.7 meq O2/kg Oil, saponification value 181 mg KOH/g Oil and iodine value 105 g I2/100 g Oil. Fatty acid composition of milk thistle oil was also analysed by gas chromatography. Among determined fatty acids, linoleic acid (39%) and oleic acid (36.7%) were the highest, followed by palmitic acid (10.1%), stearic acid (6.8%), linolenic acid (3.6%), arachidic acid (2.9%) and behenic acid (0.57%). Based on the results obtained, milk thistle seeds were rich in oil and essential fatty acids and this is important from nutritional and medicinal points of view, therefore cultivation of this oilseed for production of edible oil can be studied for consumption.

Inulin is widely used in functional foods throughout the world due to its useful nutritional and functional properties such as fat replacer, texture improvement and prebiotic effects. Salsify Plant is the one of valuable source of inulin, but few studies exist on its extraction. In this research, central composite design (CCD) was performed to investigate the effect of each variable, time (5-40 min), solvent: solid ratio (5-15 v/w) and temperature (40-90°C) on inulin extraction yield from salsify and optimization of conventional extraction of inulin. Response surface methodology (RSM) was also employed to optimize multiple variables to predict the best performance conditions with a minimum number of experiments. Chemical properties and mineral contents of salsify plant were also determined according to AOAC methods. The results of analysis of variance showed that effects of time and temperature on inulin extraction were significant (P < 0.05). The optimal conditions for maximizing inulin extraction yield (13.23%) were at 56.24°C, solvent: solid ratio of 8.97:1 (v/w) for 39 min.

One of the main deficiencies of yoghurt drink is undesirable flavor and swelling due to microbiological activation that leads to decreasing the shelf life and consumer acceptance. This study has been conducted to determine the microbiological contamination sources during production of Iranian yoghurt drink (Doogh) in three local dairy plants, situated in Mashhad, Iran. Samples were collected at sixteen different control points, which involved every stage of production from the beginning to the end. Each plant was visited three times for sampling. Microbiological analysis of all samples was performed to determine total aerobic bacteria, coliforms, psychrophilic bacteria, LAB and yeast according to the Institute of Standards and Industrial Research of Iran (ISIRI). The results showed that the hygienic quality of Doogh is dependent on the quality of raw milk, the effectiveness of heat treatment, the microbiological quality of added ingredients and packaging materials, the cleanliness of surfaces coming into contact with the Doogh and the efficiency of the plant sterilisation. Starter culture as the possible contamination sources of psychrophilic bacteria, coliform and yeast, potable water and washing water as the contamination sources for coliform and yeast, nuzzles and packaging materials as the contamination source of coliform, yeast and total aerobic and mesophilic bacteria and production room air as the contamination sources for psychrophilic bacteria, coliform and yeast were determined. Results showed that factories certainly have various contamination sources because of the unstandardized design of Doogh factories in Iran. Therefore, it is necessary to determine critical control points in all factories and organize auto-control systems in order to eliminate or at least minimize the risk of contamination.

Soy protein concentrate (SPC) which is one of the well known food ingredients, is produced especially from defatted soy flour and flash desolventized white flour with maximum PDI, but other soy flours may also be used to produce products with different properties. In this study, four different soy flours including defatted soy flour (fat content 3.67, PDI 55.10), defatted and toasted soy flour (fat content 3.78, PDI 10.72), low fat soy flour (fat content 14.34, PDI 32.71), and full fat soy flour (fat content 22.08, PDI 28.72) were used to produce SPC by two washing methods (alcohol washing and acid washing) and chemical properties and key protein functionalities were determined. SPC from full fat soy flour had higher yield but lower protein content due to its residual oil. Alcohol washing had higher yield whereas fat, protein, and fiber contents were decreased. PDI of alcohol washed SPCs had lower content and, in contrast to acid washed SPCs, did not relate to PDI of starting materials. Under the same washing condition, SPC from defatted soy flour had higher water holding capacity, fat binding capacity, emulsification, and foaming properties. SPC from acid wash procedure had higher emulsifying and foaming properties while alcohol washing enhanced water holding and fat binding capacities.

The most common disease caused by wheat protein (Gluten) ingestion is celiac, and the only effective treatment is strict adherence to a 100% gluten free diet for life. The objective of this study was to evaluate the effects of guar and microbial transglutaminase (T.G) enzyme on farinograph properties and bread quality of gluten free composite flours(Soya flour, Rice flour and corn starch). In this study, guar gum was added at two levels (2, 3%) and T.G was added at three levels (0, 1, 10 u/g pro) to the formulation. Results showed that guar addition caused increase in specific volume, but T.G had a negative effect on it. Guar addition had no effect on the crumb texture of bread, but addition of 1 u/g pro of T.G caused appropriate texture crumb in bread. Incorporation of guar decreased the crumb hardness 2 hours after baking comparing to control but with increasing the addition of T.G crumb hardness was increased. Addition of 10 u/g pro of T.G retarded the staling of gluten free breads, but guar addition had no effect on staling.

The effect of types of gums including arabic and guar on the physicochemical properties of frozen yogurt was investigated. The results showed that the gums had no effect on pH but caused a significant increase in overrun of samples (P< 0.05). The lowest overrun (22.37 %) belonged to control sample and the highest overrun value (39.38 %) belonged to sample containing 5 g/l arabic gum. In terms of viscosity, frozen yogurt with 3 g/l guar gum and control sample had the highest and lowest value, respectively. Addition of gums improved melting properties, significantly (P>0.05). The longest and the shortest first dripping time were related to samples with 5 g/l arabic gum and control sample, respectively. Melting rate of frozen yogurt also decreased significantly by addition of gums.

Despite of long use in traditional medicine, the potential of antioxidant activity of acorn fruit are still lacking. Our study goals were to assess the antioxidant potential of methanol (80%), ethanol (70%) and water extracts of Iranian acorn variety (Q.branti var persica). Total phenol content was evaluated spectrophotometrically and antioxidant activity was evaluated using three different methods including reducing power assay, scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and total antioxidant capacity and the results were compared with synthetic antioxidant, BHA and BHT. For all the methods tested the antioxidant activity was concentration dependent. Methanol extracts of acorn fruit showed the highest total phenol content (138.49 mg TAE/gr dry extract), DPPH scavenging effect (EC50= 49.5 mg/ml), reducing power (EC50=230.9 mg/ml) and total antioxidant activity (EC50=424.81 mg/ml) compared to other methods. Results indicated that in all the methods tested, antioxidant activity of BHT was significantly higher (P<0.05) than extracts. Although the antioxidant activity of methanol and ethanol extracts in scavenging effect on DPPH was greater than that of the BHA, the difference was not significant in total antioxidant capacity assay (P < 0.05). The results indicated that acorn fruit are a potential source of natural antioxidants.The activity of the methanol and ethanol extracts in the scavenging effect on DPPH was greater than that of BHA but greater than that of a-tocophero

In this study, the effect of the clove essential oil (EO) (0.1 %) and grape seed extract (GSE) (0.1 and 0.2 %) alone and in combination with each other on different spoilage related bacteria (mesophilic viable count, psychrotrophic viable count, lactic acid bacteria and Pseudomonas spp.) of raw buffalo patties was examined during inadequate refrigeration temperature (8 C) for 9 days. Results showed that until the end of storage, incorporation of 0.1% EO significantly effect the growth of Pseudomonas spp., psychrotrophic and lactic acid bacteria (P0.05) and did not affect growth of mesophilic bacteria. However, combining EO (0.1 %) and GSE (0.1 and 0.2 %) yielded any significant effect on mesophilic bacteria and Pseudomonas spp. During the storage of patties, mesophilic and psychrotrophic bacteria were most resistant and sensitive spoilage groups to the agents by 0-0.5 and 0.8 log cycles reduction, respectively. In conclusion, these findings demonstrated that in spite of the efficiency of clove EO for controlling spoilage flora of patty, GSE in mentioned concentrations had not satisfactory inhibitory activity on spoilage bacteria.

Wheat dough rheological properties are usually studied using empirical tests such as farinograph and extensigraph methods. These methods require large amounts of flour sample, which is a restrictive factor in wheat genetic and breeding studies, where small amount of flour is available. Thus, suitable rheological tests are necessary which could predict or correlate large-scale rheological tests in one hand, and involve less amount of sample on the other hand. Dough oscillatory tests require small flour samples and provide useful information about dough rheology. Since, dough major properties are determined by gluten fraction, and considering the fact that that glutenin macro-polymer (GMP) test requires less amount of sample, in this study GMP rheological test was used for evaluation of dough rheology. Correlation between dough oscillatory test parameters with farinograph parameters was carried out. Results showed that there is a significant (α<0.05) correlation between storage modulus, tan delta in GMP oscillatory test with Farinograph parameters such as dough development time, dough stability and Farinograph quality number.

The effect of two types edible coatings, based on methylcellulose (MC) and gum tragacanth (GT) in combination with soy flour on physiochemical properties of fried donuts were studied. Dough was prepared with 0, 5 and 10% substitution of wheat flour with soy flour. Dough surface coated with hydrocolloid solutions (1% w/w) then fried at 150°C. Addition of soy flour did not show significant effect on moisture and oil content of the fried donut (P>0.05) but significantly (P<0.001) reduced the volume of the fried donuts. However, coating was effective method to reduction of oil content. Because of film forming properties, GT and MC coatings significantly (P < 0.05) reduced oil uptake but they did not have significant effect (P > 0.05) on moisture content and volume of the fried donut. Farinograph evaluation of dough showed that the addition of 10% soy flour considerably (P< 0.001) increased water absorption.