Iranian Food Science and Technology Research Journal
Year:2005 | Volume:1 | Issue:1|Papers Count:10

Viscosity (m) and density (r) are important physical properties for analysis of membrane processes performance and for designing a new membrane process. In addition, the energy requirement for fluid pumping is depend on these two physical properties magnitiude. In this study, firstly, the effects of different process factors such as transmembrane pressure (51, 101, 152, 203 and 253 kPa), temperature (30, 40 and 50oC) and the effects of physicochemical properties such as milk pH (6.67, 6.43, 6.25 and 5.97), milk fat percent (0.09, 1.19, 2.4, 3.26) on the viscosity and density of permeate have been considered. Two linear Multiple regression models were then developed by Sigma stat software for prediction of m and r during milk ultrafiltration. The experimental results showed that m and r decreased as fat percent or temperature increased. pH had no considerable effect on m and r.Furtheremore, increasing transmembrane pressure to 152 kPa led to an increase in both m and r, while further increasing to 253 kPa resulted in a decrease in both m and r. The statistical modeling results showed that the viscosity is only significantly depend on temperature and there was an excellent agreement between actual and predicted data (R=0.976), whereas the density is siginificantly depends on both temperature and fat percent and there was a good agreement between experimental and predicted data (R=0.904).

Utilizing natural clay in the traditional production of the grape concentrates in the villages cause the input of large amounts of some metals (solutes) in the product which will be harmful for the consumers. To eliminate the natural clay from this procedure in nonindustrial scale, bentonite was selected as an aid-clarifier and examined in treatments under these conditions: two levels of bentonite (1gr/liter, 2gr/liter), primary temperatures of 25, 50 and 80oC, two methods of clarification (with preheating to 65oC and without preheating) and time duration 3 hours. Results showed that the clarification of the grape juice concentrate in this scale was the best when 1 gr/liter of bentonite (in jelly form) was added to juice in the room temperature and held for 3 hours before filtration with a suitable cloth and preheating to 65oC. For a product with acceptable taste it should be increased the pH of grape juice after clarification; so for this purpose the addition of Na2Co3 (about 1.5 gr/liter) is recommended.

Bulk tomato paste which is produced by most domestic factories in cocentrations more than 35% (35-40 degree of brix), and filled in to barels as bulk quantity under non -hermetic conditions. The microbial contamination level in this product is high since there is no any post heat treatment. for sterilization and microbial redaction Barels maybe stored at coldstore or ambient temperatures for more than 8 months. With limiting of raw material (tomato fruits) in winter, bulk tomato paste is reconstituted and filled in cans as or commertial conservation. On the basis of the results obtained from the evaluation of fungal contaminations in bulk tomato paste in cold store, it was determined that the main fungal flora of this product is contained different species of two genera Aspergillus and Penicillium.These moulds grow easily in temperatures near 0C and influence the qualitative properties of the product. It was found that using high brix (»38) in production of tomato paste and storing in 0C had only, limiting effect on the fungal growth and could not prevent it completely.

In this study, soymilk curd (tofu) was produced and evaluated at three stages according to Iranian preference. In the first stage, the effect of soybean varieties (Williams & Habbit), production methods (Traditional & Recommended), and formulation (0, 10 and 20% cheese whey instead of water used in soymilk production) on the qualitative and quantitative J characteristics of tofu were evaluated.In the second stage, fresh tofu was stored in brine or cheese whey containing salt at different concentrations (2, 4 & 6%) and the quality of tofu was then evaluated. In the third stage, the consumer preference and the consumption attributes were determined. The results shown that the best quality of tofu will be achieved when the Williams variety, the recommended method and 0% whey are used. Furthermore, the results indicated that the most appropriate storage medium is cheese whey with 4% salt. Such product can gain the 72% of the consumer's acceptability.

Tomato is one of the most important crops with a yeild of 98.8 million tons in more than 128, 000 hectare of area under cultivation and 3.7 million tons production in Iran. With regard to technological advancement (improvement, development) and increasing demand of tomato and their products in Iran and all over the world, it is necessary to know about affecting factors on production, process and storage of this product more precisely. In recent years, many researches have been performed to study physic-chemical and sensory characteristics of tomato in order to forecast necessary parameters in cultivating and selecting of the tomato variety corresponding to their own application (fresh eating, processing and both of them). In this research, the effect of variety and storage on physical properties of tomato paste produced from four tomato varieties (Cal.J.n.3, Early Urbana Y, Early Urbana111 and Peto early C.H) has been determined in one year storage under ambient temperature (average temperature 25oC ). The analysis of data on physical properties including: %PWR, RF Index, consistency and color showed that, Early Urbana Y had the highest consistency, PWR and total scoring for all of the properties Early Urbana Y totally was the best. Cal.j.n.3 variety in the most physical properties had the least changes during storage and from this point of view it was the most stable variety during storage of tomato paste.

The effect of thyme and ajowan essential oils (200 mg/1and 300 mg/1 respectivilly) on growth of aflatoxin-producing strain of Aspergillus parasiticus on 2 stages of pistachio (green and with dry peel) was studied. Also Organoleptic tests for evaluating odor and flavor residual of essential oils on pistachio were also performed tested.The Collected data were statistically analyzed. The results showed that thyme essential oils at 200 mg/I had stronger effect than ajowan essential oils at 300 mg/L in terms of control the growth of Aspergillus parasiticus inspite of more thymol content of ajowan which might be as a resalts of synergistic effect between thymol and other phenolic compounds such as carvacrol in thyme. evaluation of organoleptic by 13 panelists showed that the sample which was treated by ajowan oil scored as more acceptable than the others. It was concluded that both thyme ajowan essential oils are promising natural fungistatical agents and can be used instead of currently used synthetic fungicides.

Food borne viral infections are recognized increasingly as human illneses. Hepatitis A virus (HAV) is an important pathogen which has been responsible for water and many food - borne outbreeks especially milk. In this study for approaching to best diagnosis method of HAV in milk by ELISA technique, various dilutions of HAV antigen (1 ml/L, 10-3 ml/L, 10-6 ml/L, 10-9 ml/L) were added to UHT milk.Various treatments for virus (antigen) isolation, showed that milk with acidic coagulation, following filtration with paper and membrane filters, had the most optical density. It's indicated that this treatment resulted the best diagnosis (p<0/05). Also it has been revealed that this method has not any sensitivity for quantitative determination of HAV (antigen) in milk.