IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2015 | Volume:12 | Issue:46|Papers Count:21

Studies on the production of protein supplements for phenylketonuria (PKU) patients indicate that whey protein is one of the most important protein sources for production of these compounds, owning to its specific combination of amino acids. Whey is considered as one of the most polluting by-product in environment, otherwise, it is an excellent source of functional proteins that can be used in medicine and special diet products. In this study, three different concentrations of whey protein concentrate (WPC) were used as a substrate for three enzymes Flavourzyme®, Neutrase® and Protamex®. Effect of substrate concentration and hydrolysis time were studied on the separation efficiency of phenylalanine using response surface methodology (RSM) design. Phenylalanine was removed from hydrolyzed samples using ultra filtration (UF) and its concentration was measured using HPLC technique. Results of this study showed that samples hydrolyzed by Flavourzyme® contain the lowest level of phenylalanine. Also, process optimization was done in order to predict the best conditions of hydrolyzing. The best condition in order to remove the maximum phenylalanine from whey proteins was found for the minimum hydrolyzing time and the lowest substrate concentration for all three enzymes.

Unfavorable conditions in the production and storage of traditional breads, lead to a high decline in bread quality and thus severe damage and high economic losses. Hence, in this study Baked-Off Technology (BOT) and Modified Atmosphere Packaging (MAP) were used for increasing the shelf life of part-baked product. For this, part-baked Sangak bread was packaged in polyamide/polyethylene bags of 100 mm thickness with three compositions gas included %100 CO2, %50 CO2: %50 N2, %25 CO2: %75 N2 and air as a control and storage at 25oC for 21 days. During storage, quality and microbial features of product such as moisture, texture, total count and mold and yeast count was assessed at intervals of three days. The results showed moisture and texture of part-baked Sangak are not influenced by the atmosphere in the package. While the number of total microorganisms and also mold and yeasts are totally dependent on the amount of carbon dioxide used in the headspace. To increase the proportion of carbon dioxide, the growth rate of bacteria and fungi can be slow. In addition, in this study, significant effect of storage time on all of the qualitative and microbiological characteristics of part-baked Sangak was observed during storage.

The health-conscious public demands high-quality and low-calorie products that are low in fat and sugar. IN this research, the effect of fat replacement with inulin was studied. Physical properties of cake batter such as viscosity and also physicochemical properties of cake (moisture content, volume, fat, textural firmness and sensory properties) were determined. Results showed there were no significant differences in batter viscosity and moisture, volume and textural firmness between control cake and those prepared with %20 fat-replacer level (p>0.05). Increasing the level of tat-replacer from20 to %60 resulted in significant decrease in the physic-chemical properties of cakes (p<0.05). Cakes prepared with %20 replacer level hand higher mean scores for flavor and overall acceptability compared to control. Increasing the level of replacer from 20 to %60 resulted in significant decreases in all sensory properties rating scores compared to that of the control.

Antioxidants have a wide range of application in food industry. Beside by attention to rising in universal attitude to use from natural antioxidants, at this study antioxidant extracts of barberry fruits extracted by subcritical water at 120-180oC and 10-50 Bar and radical scavenging power, reduction power, stability power of edible oil matrix and amount of Total Phenolic Compounds (TPC) of extracts investigated in Folin method. Results showed that amount of Total Phenolic Compounds changed from 2073.81 until 2553.79 mg Gallic acid per 100 grams of Dry Material (mg G.A/100 g D.M) that maximum of Total Phenolic Compounds, observed at 160oC and decreased with rising temperature, whereas radical scavenging power and stability power in edible oil of extracts increase with temperature. Optimization of extraction process did at different temperatures and pressures condition for receive to maximum amount of Total Phenolic Compounds, stability power, reduction and radical scavenging.

Major data about antibiotic residues in food limited to raw material. Because food was cooked before consumption, it’s necessary to assess effect of heat treatment on antibiotic residues. The goal of this study is to evaluate effect of frying on tylosin residue in meat. Tylosin was added in three levels 4, 8 and 16 mg to 20 g minced meat samples and they were fried at 180oC during 3, 5 and 7 min. Tylosim amount was measured before and after frying by HPLC and tylosin reduction percent, samples center temperature and their weight reduction percent were determined after frying. In all treatments tylosin in fried samples was significantly less than raw samples (p<0.05). Tylosin reduction (%) amount had significant and positive correlation with frying time, sample weight percent and center temperature. By increasing frying time, weight and tylosin lost and center temperature reductions have been increased. Although frying resulted in tylosin residue reduction in meat, it isn’t grantee for this goal therefore it is necessary to reduce tylosin residue in meat by its correct consumption in animals and withdrawal period consideration.

In this study, the antibacterial aqueous extract of mountain sagebrush, Artemisia sieberi, Artemisia aucheriand Hyssopus officinalis against the bacteria such as Escherichia coli, Staphylococcus aureusand Listeria monocytogenes were investigated. The extracts were prepared by maceration and then the minimum inhibitory concentration (MIC) using the broth micro-dilution and minimal bactericidal concentration (MBC) was measured. The minimum inhibitory concentration of aqueous Artemisia aucheri and Artemisia sieberi against Escherichia coli, Staphylococcus aureusand Listeria monocytogenes was 160, 80 and 80 mgml-1 respectively. Also, the minimum inhibitory concentration of aqueous extract of hyssop against Escherichia Coli, Staphylococcus aureus and Listeria monocytogenes was 80, 40 and 40 mgml-1 respectively. Based on these results, the aqueous extracts of the three plants have the strong antibacterial effect against gram-positive bacteria. The most sensitive organism regarding extracts experiment was Listeria monocytogenes wheras the most resistant bacteria was Escherichia coli. Among the extracts, the hyssop had the highest antibacterial activity While the antibacterial activity of aqueous extract of Artemisia aucheri and Artemisia sieberi were identical.

Sourdough fermentation by lactic acid bacteria and baker's yeast with acidification of dough and producing lactic acid and acetic acid has significant effects on quality characteristics of bread. Application of liquid sourdough in bakery industry has attracted much attention due to higher dough yield, ease of transition and one-step process in order to achieve desired texture and flavor characteristics in final product. In the research, Response surface liquid methodology was used to optimize sourdough fermentation for increased acidification. Fermentation time (5.3- 18.7 hrs.), temperature (21.6- 38.4oC), and dough yield (249.6- 350.4) were considered as independent factors according to central composite design and their effects were studied in liquid sourdoughs fermented with Lactobacillus casei subsp casei, Lactobacillus fermentum and Saccharomyces cerevisiae. lactic acid and acetic acid contents and total titrable acidity (TTA) were considered as the main responses. The second order polynomial models satisfactory predicted the effects of variables on acidification properties (R2adj>0.80). Statistical analysis showed that all the responses were significantly (P<0.01) correlated to fermentation time and temperature. Increase in fermentation time and temperature was associated with an increase in lactic acid, acetic acid and TTA and fermentation time was the most affecting factor on acidification. Lactic acid was not affected by dough yield but the lower dough yield caused in high acetic acid content and acidity. Based on response surface and contour plots, the optimum conditions for maximum acidification were: fermentation time (21 hrs.), temperature (38oC) and dough yield (DY: 325).

One of the most important problems in date processing is unsuitable storage conditions, packaging types and then changing physicochemical characteristics. In this research date fruits (Kabkab variety) were packed within aerobic atmosphere and vacuumed PA/PE pouches and stored at different temperatures (-20, 4, 25 and 40oC). The samples were evaluated for textural parameters (hardness, adhesiveness, cohesiveness and springiness) monthly during the storage period up to 6 months. The storage temperature, time and packaging type greatly (P<0.01) affected hardness, cohesiveness and springiness tested in date fruits during storage. Time and packaging type had significant effects on date adhesiveness, while temperature did not affect it. All texture properties were higher in the dates stored at 40 ºC within all packaging types in sixth month. An increase of hardness was detected for atmospheric and vacuum packed dates throughout the storage period. However, it was noted that increasing was significantly greater at 40oC compared to other storage temperatures.

In the present study Protein hydrolysate was prepared from the sheep visceral (stomach and intestine) using Alcalase 2.4 L. The effect of temperature (40, 45, 50 and 55oC), time (in six levels) and enzyme/substrate ratio (30, 60 and 90 Anson unit), on degree of hydrolysis and antioxidant activity were investigated using factorial experiment. The highest degree of hydrolysis was observed at 45oC, after 180 min and enzyme/substrate ratio of 90 Anson unit/ Kg substrate (p<0.05). Under these conditions, degree of hydrolysis was 36.92%. To study the antioxidant activity of protein hydrolysate, DPPH radical scavenging activity, ferric reducing power and effect of protein hydrolysate on stability of soybean oil were measured. All antioxidant activity experiments were performed at constant temperature (45oC). The highest DPPH radical scavenging activity and ferric reducing power were achieved after 150 min at enzyme/substrate ratio of 90 Anson unit/ Kg substrate (p<0.05) and after 180 min at 90 Anson unit/ Kg substrate (p<0.05), respectively. Results show that protein hydrolysate can be used as a natural antioxidant source instead of synthetic antioxidants.

Mayonnaise is a kind of oil in water emulsion, that most widely used sauce in the world. Egg yolk is a key ingredient in mayonnaise, due to excellent emulsifying properties. Nevertheless, one main problem with egg yolk is its high cholesterol content, so different attempts have been carried out to develop low cholesterol mayonnaise. The aim of this study was to prepare low cholesterol mayonnaise containing wheat germ protein isolate (WGPI) and xanthan gum (XG) as egg yolk substitutes. The mayonnaise prepared with different composition of WGPI, egg yolk (0-9% of each component) and XG (0-0.5%), as formula variables by applying the optimal mixture design approach. Effect of this substitution on rheological characteristics and microstructure of mayonnaise samples were evaluated. The results indicated that all mayonnaise samples exhibited thixotropic shear thining behavior under steady shear tests, which fitted by Power law model and the factors related to this model were specified in the samples. Also, it was observed that mayonnaises exhibited weak- gel like properties, by using dynamic oscillatory shear tests and had significant effects on acquired parameters from frequency sweep test, such as storage modulus, loss modulus and tan delta. According to rheological and microstructure results, the low cholesterol mayonnaise contained WGPI and XG shows similar characteristics to those of a typical mayonnaise. Formulation 10 (71.5% and 4.2% egg replacement with WGPI and XG, respectively) shows the most similarity to control sample.

Microbial spoilage and staling are the most important reasons for the amount of bread waste. In order to extend the bread shelf life, either different bread improvers such as hydrocolloids or appropriate specific packaging like modified atmosphere packaging (MAP) can apply. In this study, the effects of hydrocolloid on quality properties of Sangak bread were investigated. The gum Hydroxypropylmethylcellulose (HPMC) was added to the formulation at 0.5 and 1% (w/w of flour) concentration. As a control, no gum added formulations were used. Wheat bread samples were packaged in polyamid/ polyethylene bags with different gas combinations. Two gas concentrations tested included: air, and 100% CO2. All packaged bread samples were stored at 25°C for 15 days. Quality and microbial features of bread such as moisture, texture, and mold and yeast count were assessed at intervals of three days during storage.Statistical analysis of the results of bread quality characteristics during storage revealed that, the gas in headspace of package did not significantly affect the product moisture content, while shear stress, maximum force and the microbial load of the samples were thoroughly impressed by it. So that with carbon dioxide, the growth of mold and yeasts was more limited. Also was observed all product quality characteristics change significantly during storage time. So that the reduced moisture were observed up to 12th day. Conversely hardness, shear stress and microbial load increased during the storage period. The breads containing 1% HPMC showed the lowest maximum force and shear stress. Control showed the highest moisture and mold and yeast count all over the storage period.

Yoghurt is one of the fermented dairy products with high nutritional value and short shelf life where its shelf-life can be prolonged by drying. Therefore, in the present study, the fresh yoghurt with different amounts of dry matter (10, 20 and 28% w/w) was dehydrated by microwave-vacuum dryer at different levels of microwave powers (35, 135, and 260 W) and definite absolute pressure (125±5 mbar). Then, the effects of type (gum tragacanth, guar gum, locust bean gum, Persian gum, and casein powder), quantity (0.25, 0.5, 0.75 and 1% w/w) in singular and combined forms (tragacanth: guar, Tragacanth: locust been gum, and guar: locust been gum), combination ratio (80: 20, 50: 50), and adding stage (pre/post drying) of hydroclloids over sensory and rheological properties of instant yoghurt were evaluated. Results showed that higher microwave powers and dry matter percent led to the shorter and higher drying rate, respectively. Regarding rheological properties, the storage modulus was significantly higher than loss modulus (G'>G'') and elastic behavior was observed in majority of samples. However, sample with Guar: locust bean gums showed inverse features, also Complex viscosity and loss tangent of most samples (pre drying method) were similar to control, except one with guar: locust been gum. Furthermore, the most accepted reconstituted yoghurt was one containing gum tragacanth, and baking powder followed by one with 0.6% tragacanth: locust bean gum (80: 20, 0.6%) which were prepared with pre-drying method. Moreover, it was found that the adding stage of hydrocolloids had significant effect on the evaluated properties of instant yoghurt where pre-drying method was recognized as the most appropriate one.

Traditional dairy products harbor a complex microbiota composed by several microbial groups, including lactic acid bacteria (LAB) and yeasts. The common method to detect LAB is to culture the products on media containing cycloheximide (CHX) to prevent yeast growth by interfering with protein synthesis. However, some yeast species and strains show natural or acquired resistance to this antibiotic and thus can be specifically selected in media with CHX. The aim of this research was to identify such CHX-resistant yeasts. To this purpose, 25 samples of home-made dairy products were plated on MRS medium with 0.01% CHX; after incubation (48 h, 30oC), 32 colonies of presumptive yeasts were picked up. Catalase test and morphological investigation confirmed that 19 were yeasts.  After DNA isolation, randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) with primer M13 was applied to gain information on genomic relatedness among isolates. Visual comparison of RAPD-PCR pattern allowed selecting five representative isolates for further analysis. Primers ITS1 and ITS4 were used for specific amplification, and the PCR-products were sequenced after purification. The results of sequencing revealed that all isolates belong to Kluyveromyces marxianus, a species with a high technological potential.

Pesticides are found in fresh fruits, vegetables and different processed products as well. In this research, diazinon residue in tomato and also effect of different processes in tomato paste production on residue amount was studied. Applying HPTLC method, measurement of the pesticide residues was carried out on arrival, before washing, after washing and rinsing, in the juice, after concentration, and in the tomato pomace. In this study two different kinds of spiking on the tomato fruit was used: Immerging of tomatoes into 2 ppt solution of diazinon and water for one and ten minutes. Samples were analyzed in triplicate and the standard deviation was 2.63. Effect of chlorination on reducing the pesticide residues level was also measured after ten minutes dipping. Experimental results revealed that diazinon residues in tomatoes after one and ten minutes dipping were 16.56 and 19.8mg/g, respectively. Effect of different processes during tomato paste production on residue amount after one and ten minutes dipping were as follow: after washing was 13.04, 16.6μg/g, in the juice and in the tomato pomace samples was 12, 13.68 mg/g and 30.52, 39.96 mg/g. tomato paste sample was 8.84 mg/g for ten minutes dipping. Effect of chlorination on reducing the pesticide residues level of measured 24.96μg/g, for ten minutes dipping.

In current study, rotatable response surface method was employed for optimizing the effect of dough mixing time in low speed (MTLS) (63 rpm, 2-8 min) and dough mixing time in high speed (MTHS) (180 rpm, 2-8 min) on bread quality (moisture, water activity and specific volume) and shelf life (bread hardness during 6 days) of Barbari bread. The results showed that linear term of MTHS was effective factor on moisture and bread hardness in day 4. Water activity and specific volume was forcefully affected with quadratic effects of MTHS and MTLS. Besides, interaction terms of MTHS×MTLS has the highest effect on bread hardness during storage. The best bread quality and shelf life was achieved in 7.24 min MTHS and 3.45 min MTLS.

The effects of microwaves on physicochemical properties of corn and oat starches were investigated.  Separate suspensions of corn and oat starches in distilled water (8% w/w) were made and heated in a microwave oven at frequency of 2450 MHz and power of 360 W for 2.5, 5, 7.5 and 10 min. Then, swelling power, solubility, relative viscosity (using U-tube viscometer), cold water viscosity (using Rapid Visco Analyser) and textural properties (using Texture Profile Analyser) were investigated. Results showed that as the time of microwave processing increased, cold water viscosity and gel hardness decreased, however, swelling power and water solubility increased. Comparing to the conventional heating method, more reduction in the relative viscosity was observed for the microwave processed samples. In general, results showed that microwave processing had a stonger effects on structural and molecular properties of corn and oat starches than the conventional cooking. These changes may be further affect the quality of the final products.

Staphylococcus aureus is one of the pathogens that causing food poisoning in humans. According to the methods of preparing the traditional raw milk cheeses and various ways of enterance of S. aureus to milk, survey of contamination of cheeses by this bacterium, may help to decrease of food poisoning caused by this microorganism. In this study 80 cheese samples (200g) produced from sheep milk randomly chosen from Marand County and detection of this microorganism was done. Diluted samples cultured in the broth agar, and then colonies in the basis of conformation divided into four groups. Coagulase test was performed on the some colonies of each group and catalase positive colonies cultured in nutrient agar. Complementary test like glucose, manitol and coagulase reveal the coagulase positive organism. Finally the black, shining and convex colonies in Baird parker agar were counted. We found that all samples (80 cottage cheeses samples) were contaminated by this organism. 6.25% of samples contain more than 105 bacteria in each gram and 16.25% have 104-105 bacteria in each gram. In according to this study control and monitoring of dairy producer should be more and do not use non-pasteurized dairy product especially cottage cheeses.

Near infrared reflectance spectroscopy (NIRS) is a nondestructive and rapid technique applied increasingly for food quality evaluation in recent years. In this research optical method based on nearinfrared spectroscopy (900-1600 nm) has been used to determine sugar content in sugar beet. A total of 120 samples were used for the modeling, whereas 80 samples were used for the calibration set and 40 samples were used for prediction set. Four pre-processing methods, including average smoothing, multiplicative scatter correction (MSC), first and second derivatives, were applied to improve the predictive ability of the models. Then models were developed by partial least squares (PLS). The correlation coefficient (r) and root mean square error of prediction (RMSEP) were 0.84 and 1.8 for SC, whereas 0.95 and 1.7 for SSC, respectively. The results show that NIR can be used as a rapid method to determine soluble solid content and sucrose in sugar beet.