نشریه فرآوری و نگهداری مواد غذایی
پیاپی 3 (پاییز 1388)

Freezing causes changes on chemical and microbial quality of butter. In this research, effects of two different temperatures -9 and -18oC on changes of moisture, fat, acidity and peroxide value and also Coliform and Psychrotrophic microorganisms in frozen butter were studied. Results showed that values of moisture and fat during 7 months of frozen storage at two temperatures decreased 1.8% and increased 1.78%, respectively. Acidity and peroxide value during 7 months of storage at two temperatures had no significant difference changes (P<0.05). Coliform microorganisms were destroyed after 2 months of freezing and the numbers of cells became zero. The numbers of Physchrotrophic microorganisms did not out of the range of standard in all and at -18oC in compare to -9 oC was decreased more. Effects of storage temperatures and different weights on the chemical and microbial quality of butter were not significant (P<0.05).

Estimation of fillet biochemical composition and processing yield is primary needs for fish processing. Present study was aimed to investigate for determining fillet biochemical composition and processing yield of bighead (Hypophthalmichthys nobilis) for nutritional labeling and economical estimation of its products by regression equations. For this purpose 55 specimen of bighead were applied in range of marketing size and their fillet yield, moisture, lipid, protein, ash and energy content were measured in wet and dry weight. Then the relationships between these parameters with fish size were considered and types of their relationships were determined. According to obtained results, the relationship between logarithm of moisture and ash with logarithm of total length and weight were inverse linear regression (P<0.05) but the relationships between lipid, protein, energy content and fillet yield with total length and weight were positive linear regression (P<0.05). In generally these equations are in form Y=bX±a. with regarded to these relationships and determining their equations, it could be sorted fishes by machine, then it could be done by obtained equations for economical estimation and determining moisture, lipid, protein, ash and energy content of each group for nutritional labeling.

Lycopene is a natural and dominant pigment in tomato which today its extraction enhancement from tomato and tomato products is trying. In this study at first wed use pectinase at 25, 30, 35 and 40 ml/Kg concentration at 0, 30, 60, 90, 120 and 180 effecting time in 55 0C constant temperature incubation. Then before extraction half of samples were washed with 94% ethanol at 60 0C for 5 second. It has been shown that in these conditions lycopene concentration in oleoresins enhances with enzyme concentration and lycopene drived from ethanol treated samples were higher than samples untreated with ethanol (P<0.01). In samples treated with ethanol maximum lycopene in 110 g oleoresin was 10744.5 mg at 35 ml/Kg at 60 min whereas in samples untreated with ethanol lycopene concentration was 3524.63mg/ 100g oleoresin at 40ml/Kg at 180 min. Lycopene extraction yield from 100 g dried tomato peel in these conditions were 10744.5 and 7930.43 in samples treated and untreated with ethanol, respectively.

In this study, binding ability of Lactobacillus rhamnosus LGG to aflatoxin of pistachio was investigated. Results indicate that the bacterium has aflatoxin surface binding ability of 35% (with initial concentration of 10 ppb aflatoxin) in exponential phase. Acid and heat treatment increase this ability to 85%. In the second concentration of aflatoxin (20 ppb), this binding ability for viable cells and acid, heat treated cells increased to 60% and 90%, respectively. Binding appears to be a physical phenomenon that reaches to maximum point within first 2-3 hours of process. Also, results showed that bacteria immobilization on aflatoxin contaminated pistachio had no effect on color and peroxide value. Bacteria cells, viable or nonviable, are effective in aflatoxin binding and this property is considered as a good solution, especially for foods having high risk of aflatoxin contamination.

Many Factors can affect wheat gluten properties and functionality. One of the most important, factors is the wheat bug damages. Insect injects a salivery proteinase into wheat kernel that causes weakening of gluten, substansial losses in physical quality, dough properties and baking performance. Bread baked with the insect-damaged flour has a much lower volume, poor crumb sensory quality (texture, colour, odour and taste). Gum and oxidant agents are interesting alternatives as chemical improvers, for flour with low or weak gluten. In this study effects of guar gum and ascorbic acid to improve chemical, rheological and baking properties of bug damaged flour were investigated. Guar and ascorbic acid were added in 3 levels: 0.5, 1, 1.5 percent and 100, 150, 200 ppm respectively. Data were analyzed in factorial experiment design and the means were evaluated in form of mathematical models with 3d- surface charts. Results showed that bread baked with bug damaged flour had poor quality and low sensory scores. Addition of guar and ascorbic acid could improve dough and bread quality but the best treatment was addition of 0.5 percent guar and 200 ppm ascorbic acid together.

During storage, serum separation is a major defect that affects the market share of Doogh. Therefore, in the present study the effects of high shear stirring and homogenization, as major operation units, on the stability was investigated. To do so, Dooghs were stirred at various speeds and time scales (9000 rpm and 11000 rpm for 30 s and 2 min), homogenized at different pressures (0, 20, 50, 80, 100, 120, 150, 180 and 200 bar), as well as treated at combined conditions of agitation and homogenization (9000 rpm, 1 min; 11000 rpm, 1 min; 100 and 200 bar) and their effects on serum separation of Iranian Doogh (59.3% water, 0.7% salt and 40% yoghurt) were studied. Our results revealed that shear stirring and homogenization could significantly increase serum separation in comparison with control where the effect of stirring speed was more pronounced (P<0.01). Moreover, the influence of their combination was considerablely higher than their effects in a single form. In addition, following all these treatments the apparent viscosity reduced and a significant increase in serum separation perceived.

In this study, moisture dependent physical, mechanical and nutritional properties of sesame seed were evaluated. In the moisture range of 4.54–19.27% (d.b.), seed length, width, thickness, arithmetic mean diameter and geometric mean diameter increased linearly from 2.93 to 3.01 mm, 1.74 to 1.78 mm, 0.78 to 0.86 mm, 1.81 to 1.88 mm and 1.58 to 1.66 mm respectively with increase in moisture content. The sphericity, surface area, one thousand seed mass, true density and porosity increased from 54.04 to 55.25%, 6.68 to 7.35 mm2, 2.43 to 2.75 g, 1207 to 1236.8 kg/m3 and 51.03 to 53.12%, respectively, while bulk density decreased from 591 to 579.5 kg/m3. The terminal velocity and angle of repose increased from 4.95 to 5.4 m/s and 31.5 to 32.8º, respectively. The highest static coefficient of friction was found on the plywood surface. The static coefficient of friction increased from 0.54 to 0.56, 0.50 to 0.54 and 0.41 to 0.45 for plywood, steel and galvanized iron sheet, respectively. The results of mechanical test showed that the force required for initiating seed rupture decreased from 25.66 to 18.36 N and 27.56 to 21.20 N, and the energy absorbed at seed rupture increased from 15.52 to 18.08 mJ and 15.84 to 18.33 mJ, with increase in moisture content from 4.54% to 19.27% d.b., for vertical and horizontal orientations, respectively. Sesame seeds contained high amounts of oil (46.57%), crude protein (23.75%) and calcium (0.98%). The mineral contents of the seed for Phosphorus, Potassium, Magnesium and Iron were 508.3, 486.7, 288.2 and 10.7 mg/100g of dry matter, respectively. The major fatty acids were oleic acid (43.4%), followed by linoleic acid (36.3%), palmitic acid (11.75%) and stearic acid (6.25%).

Triticale (X Triticosecale wittmack) is a hybrid seed plant result from wheat and secale. This seed has high amylolitic and protelytic activities, introducing it as adjuncts in mashing process. In this study, influence of malting process on physico-chemical properties variety of barley (namely Sahra) and Triticale and malt quality of them were investigate. Malt of barley was selected as reference and the effect of adding unmalted triticale, as adjunct, in malt of barley (20, 40, 50 %), on physico-chemical properties of wort such as diastatic power, cold water extract, hot water extract, color and pH was investigated. Results showed malting of these grains, induce an improved in diastatic power and cold water extract and a decreased in total nitrogen and ash content. Mixing of 20% triticale produced more hot water, total soluble, nitrogen extract, dry matter, and reduced sugar while the lowest value observed in mixing of 50%.

Present study examined the effect of storage conditions (packaging type, storage temperature and time) on physicochemical and microbial properties of tomato juice. Samples were stored for one and three months in two packaging types (bottle and doypack) at 4, 25 and 35oC. Results obtained from testes (pH changes, acidity, solid soluble content, vitamin C content, and microbial load) showed that no significant differences are observed in the quality of both kinds of tomato juice packed. However duration and temperature of storage have significant effects on microbial specification and nutrition value (vitamin C content) of tomato juice. It proves that samples were stored at 4˚C for a period of one month had the best quality.

This study was conducted to evaluate the effects of freeze-thaw cycles on some quality parameters of silver carp fillets. The prepared fillets were packaged in zip lock bags and were subjected to 0, 1, 2, 3, 4 and 5 freeze-thaw cycles, respectively. Heme iron content decreased, and dry matter increased as the number of freeze-thaw cycles increased (P<0.05). In the fillets that were thawed 1, 2 and 5 times, free drip loss on cooking were significantly (P<0.05) more than fresh fillets. The highest water holding capacity observed in the highest pH value. L*, a*, b* and total color difference values (from the fresh sample) (∆E) increase with increasing freeze-thaw cycles. Folding test showed that, gel forming ability of silver carp fillets decreased with increasing freeze-thaw cycles. The results revealed that multiple freeze-thaw have undesirable effects on physical and chemical quality of fillets, therefore re-freezing of thawed fillets is not recommend.