JOURNAL OF FOOD RESEARCH (UNIVERSITY OF TABRIZ)
Year:2012 | Volume:22 | Issue:1|Papers Count:10

Scaling methods has many equations that are used to create the general flow curve to describe flow behavior of systems with different viscosity, density and particle size. These methods can give a general flow curve for all concentrations in non-Newtonian media and a general flow curve obtained from one sample can be used to predict the flow curves of the same samples with different viscosities. The aim of this study was to evaluate various scaling and rheological model to investigate the flow curves of various suspensions consisting of tragacanth gum (TG) (0.5, 1% wt) and whey protein isolate (2, 4% wt), and to determine the best-scaling law and rheological model. The scaling methods were relative viscosity, Peclet number, and Reynolds number. The results showed that the best scaling method is Peclet number. The flow behavior of all samples was successfully modeled with the power-law, Ellis, and Cross models; the power-law model was found to the best describe the flow behavior of dispersions. The flow behavior index decreased and consistency index increased when TG concentration increased.

Wheat starch is the most famous type of starch in many parts of the world. The health beneficial effects of oat have been well documented. However, less information is available on the physicochemical properties of oat starch and its derivatives. The main aim of this study was to compare the effects of hydroxyporpylation on wheat and oat starch gels. Therefore, wheat and oat starch were hydroxypropylated using 30 mL propylene oxide at 40 °C for 24 h. The texture of the starch gels (10% starch solid) was determined using a Stable Micro Systems TAXT-2i Texture Analyzer. From the resulting force/deformation curves, the textural parameters of hardness, work, cohesiveness, springiness, gumminess and chewiness were calculated. The results showed, the hydroxypropylationion of wheat starch reduced gel firmness, while it enhanced oat starch gel hardness.

In this study, the optimum condition for producing pre-cooked and dried red kidney bean with shorter cooking time than the ordinary red kidney bean was determined. Therefore, red kidney bean was soaked in water at different temperatures (25, 40 and 60 °C) and then was pre-cooked at 93 °C until it became soft. Then it was dried using hot air at different temperatures (50, 60 and 70 °C).The results showed that with increasing the soaking temperature, the speed of water absorption, the time required for drying and cooking time of the beans increased. The pre-cooked and dried samples had lighter color than the ordinary beans. No need for soaking and almost 50% shorter cooking time than the ordinary beans were the advantages of this product. Based on the results of this study to produce pre-cooked red kidney bean, using 50 °C water for soaking and 40 °C air for drying are suggested.

Walnut usually classified in different quality groups due to its high economic price and therefore it is required to determine physical properties of it, especially obtaining the necessary information for designing sorting and grading machines. In this research, the physical properties of Kaghazi cultivar of walnut, including dimensional properties: length, width, thickness, arithmetic mean diameter, geometric mean diameter, roundness, surface area, and also gravitational properties: mass, volume and true density and their variations were determined in three quality groups of white sound, dark sound and damaged kernels. The results indicated that the mean values of length, width, thickness, arithmetic mean diameter, geometric mean diameter, roundness, surface area, mass, volume and true density were equal to 27.74mm, 26.32mm, 10.78mm, 21.61mm, 19.85mm, 0.72, 1243.68mm2, 2.90gr, 2850mm3 and 1.03gr/mm3 in white sound kernels, respectively. In addition, the results of ANOVA showed a significant difference between quality groups based these physical quantities. In this relation, it is possible to distinguish between sound and damaged kernels according to their mass, volume and density. However, according to frequency diagrams of physical properties, it is not possible to reach the 100% of separation. Therefore, it is necessary to use a series of separating units, in which every unit use a specific property.

The effect of adding microbial transglutaminase either with rennin or after cutting the cheese curd was studied on chemical, textural and microstructural properties of low-fat Iranian White cheese. In both cases, addition of transglutaminase increased the moisture content, cheese yield, protein recovery and ratio of moisture to protein.Treatment of cut curd with transglutaminase led to a higher ratio of moisture to protein and less stress at fracture and young’s modulus. Transglutaminase yielded in a network with porous microstructure and reduced compaction.

Mentha spp. has been used as a folk remedy for treatment of nausea, bronchitis, flatulence, anorexia, ulcerative colitis, and liver complaints due to its ant inflammatory, carminative, antiemetic, diaphoretic, antispasmodic, analgesic, stimulant, emmenagogue, and anticatharrhal activities. This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Menthe long folia Hudson. Total phenolic constituent of the extract was 4.5 g/100 gas Gallic acid equivalent. GC–MS analysis of the oil resulted in the identification of 45 constituents, cis-piperitone epoxide, polygene and piperitenone oxide being the main components. Antioxidant activity was evaluated through 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay and b-carotene/linoleic acid assay. The essential oil and methanol extract were individually tested (disc-diffusion assay and evaluating minimum inhibition concentration (MIC)) against a number of bacteria. The essential oil showed strong antimicrobial activity against bacteria tested whereas the methanol extract almost remained inactive. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g. in the inhibition of free radical 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and b-carotene/linoleic acid systems. In the former, the extract was able to reduce the stable free radical DPPH with an IC50 of 55.3 mg/ml while that of the oils was 10630 mg/ml. When compared to BHT, a synthetic antioxidant, both showed weaker ant oxidative potential. Similarly, in b-carotene/linoleic acid assay, these samples were not effectively able to inhibit the linoleic acid oxidation; exhibiting only 24% and 36% inhibitions at 2 mg/ml, respectively; both were far below than that of BHT.

The aim of this study was extraction of phenolic compounds from Touyserkani variety of walnut husks with two extraction methods (traditional method and with microwave assisted extraction (MAE)) and with solvents (methanol 80%, ethanol 50% and water) in different times. Total Phenolic contents were determined by Folin Ciocaltue assay. Then the antioxidant activity of extracts was assessed through reducing power assay, DPPH radical-scavenging activity and total antioxidant activity. The results showed boiling water in traditional method and methanol 80% in microwave assisted extraction were optimum solvents. Lowest IC50 in DPPH radical-scavenging activity in traditional method was water extract and it in MAE was ethanolic extract. Finally, effects of methanol extract in retarding the soy oil oxidation were examined. Methanol extract with the concentration of 1000 ppm could control oxidation. Result of this study showed that walnut husk is a potential source of natural antioxidants.

Battered foods are popular due to appearance and taste characteristics such as their crispy texture, desirable color and flavor. The quality of coated products is influenced by rheological properties of the batter. In this study, the rheological properties of two types of batters (batter with typical formulation and batter with 2% Methyl Cellulose) were investigated. The batters were formulated using different ratios of wheat, soy and corn flours. The batters in power-law model showed shear-thinning behavior. The rheological properties varied with different types of flours and their combination ratios. MC increases the batter consistency and enhanced the shear-thinning behavior of the batters. The values of flow behavior index (n) in different batter formulations were found between 0.36 to 0.62. Batters viscosity varied from 0.68 to 7.33 Pa.s at 200 s -1 shear rates. In all samples, batter with 50% soy flour provided the highest apparent viscosity among all formulations.

This study was conducted for evaluating the effects of two chemicals on quality and shelf-life of plum cultivar "Golden Drop". The experiment was carried out with five treatments and six weeks storage as a factorial experiment with a complete randomized design with three replications. The quality characteristics of fruit such as weight loss, fruit firmness, soluble solids contents, pH, titratable acidity and ascorbic acid were assessed in summer 2010 at flowering biology and developmental physiology lab, University of Tabriz. Treatments were the concentrations of 60 and 80 mM calcium chloride and 1 and 3 mM salicylic acid and distilled water (control treatment). After treatment with dipping method, fruits kept into a cold room with a temperature of 1-2 °C and 80% relative humidity and then qualitative parameters were measured every week. Results showed that effect of treatment and time was significant in all characteristics at 1%. Time and treatment interaction on fruit firmness and soluble solids contents was not significant, whilst interaction effect treatment and time on weight loss, pH, titratable acidity in statistical level 1% and ascorbic acid content had significant diversity in statistical levels 5%. Mean comparisons showed that between control and other treatments were significant differences in all characteristics. Calcium chloride solution of 60 mM was the best treatment for the maintenance fruits vitamin C content.

A symbiotic ice cream containing 1% of resistant starch as a prebiotic component and two strains of lactic acid bacteria (L. casei and B. lactis) as probiotic bacteria was made by traditional ice cream manufacturing method. The survival of microencapsulated and free probiotics in ice cream was studied over a period of 6 months during storage at -20°C. Microencapsulated probiotics in alginate-starch beads were survived 30% more than encapsulated bacteria. So the number of viable probiotic bacteria in functional ice cream were more than 109 CFU/g by two months, which is higher than that recommended by the International Dairy Federation (107 CFU/g). In conclusions symbiotic ice cream is a good vehicle for delivery of probiotics in human diet.