IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2008 | Volume:5 | Issue:2|Papers Count:15

The effect of CO2 (0.5 l min-1 for 15 min) and orange juice (30% v/v carrot juice) on phisico-chemical characteristics as well as microbial flora of carrot juice within the three months of storage was investigated. Both orange juice and CO2 caused a decrease in pH value of carrot juice but pH reduction was higher when orange juice (30 percent) was added. Samples of carrot-orange juice had higher value of acidity and lower pH. Blending orange juice with carrot juice caused higher percentage of precipitation, decrease in a* and b* values and increase in L* value. The results of this experiment showed that sugar decreases the percentage of precipitation in pasteurized carrot juice. No microbial growth was detected in either of the treatments.

Texture quality factors of two apple varieties after cold storage duration are evaluated by Magness-Taylor and fruit pressure tester instruments in the same conditions. Force (N) Force/area (F/cm2) and Force/Deformation (F/mm) were determined .All of obtained results were statistically analyzed by Randomized Complete Block Design and means separated by Duncan Multiple Range Test .The results were showed that ,the texture strength and quality of Red delicious apple is better than Golden delicious after cold storage duration. Also the texture quality factors obtained by fruit pressure tester in the same conditions are always more than Magness Taylor and there are high significant differences between the results of two instruments. For prevent of any mistake in evaluating of maturity and texture quality of apples any instruments must be evaluated individually and there is no similarity between the results of them.

In order to determine the effect of different ripening time and ripening temperature conditions on the flavor, aroma and texture development and its acceptability for consumer and also selecting the optimum conditions of cheese ripening ,an analysis was done with CRD test and three replications on 4 types of cheese having different ripening conditions including: traditional cheese A (two weeks at 16oC and one month at 4oC)-traditional cheese B (one week at room temperature and one month at 14oC)- UF-C cheese (one day at room temperature and 10 days at 18oC and two weeks at 4oC)-UF-D cheese(one day at 25oC and 4 days at 4oC). Chemical properties such as NPN/TN (non protein nitrogen to total nitrogen), ADV (acid degree value) and total acceptance at different storage time analyzed. The results showed that traditional cheese A and UF-D had the largest and lowest contents of NPN/TN, ADV and total acceptance, respectively. The effect of increasing NPN/TN, ADV on sensorial characteristics and total acceptance of cheese was not significant for UF-D only, and total acceptance increase showed the maximum amounts at the initial two weeks in the other samples. At the same time and temperature, traditional cheese had larger amounts of NPN/TN but UF type cheese had larger amounts of ADV. Modeling of the results by Response Surface Method indicated that the effect of increasing values of ADV (lipolysis) was greater than NPN/TN (proteolysis) on the intensity of cheese ripening process and total acceptance, and therefore between 4 types of cheese optimum ripening conditions was for traditional B.

In this research diacetyl production as a buttery flavor in food industries by Lactic Acid Bacteria (LAB), Lactococcus and Leuconostoc genus was investigated. Batch fermentation process accomplished on MRS (De Man, Rogosa and Sharpe medium) broth medium, medium based on whey powder and based on skim milk powder at different conditions of temperature, agitation speed, glucose as carbon source, tri-sodium citrate as precursor of diacetyl production, inoculum, catalase enzyme, bovin blood as heme protein source and CuCl2. Optimum conditions were determined for achivement of highest production yield. This research indicated that the optimum fermentation conditions for diacetyl production by LAB were: 32oC, 180 rpm, glucose 6 g/l, tri-sodium citrate 5g/l, inoculun 5%, catalase enzyme 6 ml/l, bovin blood 4 g/l, CuCl2 15 mg/l. Finally, for production of diacetyl, a fermenter was used with 10 liter volume, inoculum size 5% (v/v) with working volume of 6.5 liters. Agitation and temprature were maintained at 180 rpm and 320C, respectively. Diacetyl concentration under optimized condition in fermenter was obtained as 945 mg/l.

The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging. There are many studies about antimicrobial properties of spice extracts; however their application to edible films is limited. In this study chitosan-based edible films containing thyme and clove essential oils were prepared at 0.5, 1 and 1.5 percent v/v. Antibacterial properties of edible films were tested against five strains of Gram-positive and Gram-negative bacteria. Physical and mechanical properties of films including humidity content, water vapor permeability, tensile strength and elongation at break were measured. Films containing thyme essential oil showed larger inhibitory zones (p<0.05) compared to those of containing clove essential oil. Films were more effective against Gram-positive bacteria than Gram-negative ones. Incorporation of essential oils increased water vapor permeability of chitosan-based films. Incorporation of essential oils decreased tensile strength of films. Films containing thyme essential oil showed larger reduction in tensile strength property compared to those of containing clove essential oil.

Iranian tea industry problems caused to related section damage. Low quality of Iranian black tea and change in sense of consumers taste is one of the reasons. It is produced various teas to attract of consumer opinion. Permissible additives using is not usual in Iranian tea industry (before packaging). One of the natural additives of black tea (i.e. Qare-Qat) evaluated in this experiment. The experiment carried out by using a Split-Plot with two factors in three replications. Storage period was distributed in four levels (0, 2, 4 and 6 months) in main plots and added Qare-Qat fruit amount in subplots in four levels (0, 5%, 10% and 15%). Qualitative traits of tea including organoleptical tests (as made tea apparent, color, perfume, and flavor of tea beverage) and chemical tests (as measuring of theaflavin (TF), thearubigin (TR), total color (TC) and brightness (B) of tea) studied. Chemical tests results showed that "Tea + 5 and 10 percent Qare-Qat fruits" treatment has more TF, B and TF/TR ratio than control (pure tea) and this difference was significance in 1% level. However, taste tests did not revealed significance difference between control and tea + Qare-Qat blends.

Effect of two storage temperatures -14±2oc and-28±2oc was investigated on distribution and redistribution of Fe, Cu, Zn, Mg, Mn, Hg, Pb and Cd metals in tissue and viscera of green back mullet. Statical results showed that average amount of Fe metal in tissue of mature and immature fish stored at -14oc (respectively 77.1 ppm and 166.6 ppm) was more than both fresh mature and immature fish (28.5 ppm and 88.1 ppm) and fish stored at-28oc (26 ppm and 109.1 ppm). Amount of Zn metal in the viscera of mature fish stored at-28oc (56.8 ppm) was more than fresh fish (43.5 ppm) and fish stored at-14oc (43.5 ppm). Likewise amount of Pb metal in the viscera of immature fish (59.9 ppm) and fish stored at-14oc (58.3 ppm) was less than immature fish stored at-28oc (110.2 ppm). Considering that the amount of other metal did not show significant changes during frozen storage, it seems that-28oc temperatures provides better quality from the view point of distribution and redistribution of heavy metals, and fish tissues stored at this temperature have more food immunity and health for consumers.

Losses of agricultural products and the related financial losses are considerable in Iran. Potato is one of the most important crops in Iran and has the most nutritious energy per area. The losses of potato are considerable as statistical reports. The mechanical damage is one of the factors in potato losses that occur during harvesting and handling of potato tubers. When reduction in mechanical damage of tubers is of concern, attentions are automatically drawn towards the design and adjustment of the potato harvester. Of course the design and adjustment of the potato harvester is one of the coin, the other side is the potato tuber themselves. For some potato varieties that are highly susceptible to mechanical damages, even a well designed and adjusted harvester can still cause extensive damage. For this reason a prior knowledge about damaging impact energy threshold of potato tubers are as important as the knowledge about the harvester.In this research a constructed pendulum was used to measure the damaging impact energy threshold for Agria, Aula, Marfona varieties. After measuring volume of damage, the effect of impact angle, varieties and tuber size were studied.Results show that, varieties, impact angle and tuber size has significant effect on the volume of damage and aula variety is more susceptible to damage than other varieties. Although volume of damage in large tubers are higher than other sizes.

This study was conducted to produce UF white cheese with the mixture of KCl and NaCl salts and its effect on microbial properties including Total Count, Mould, Yeasts and Coliforms and Compositional properties such as moisture, fat, total nitrogen and water soluble nitrogen. Changes in acid degree values (ADV) in all treatments were also investigated.  Four treatments of low-salt White Cheese with salt ratios of NaCl/KCl: 1.50: 1.50 (A) 1.00: 2.00 (B) 0.75: 2.25 (C) and 3.00:00 (D, as control) were prepared by dry salting practice. The samples salted with various proportions of NaCl and KCl had significantly (P<0.001) lower bacterial counts than those salted only with NaCl. The lowest bacterial count was observed in treatment C. Neither mold and yeast nor coliform bacteria was detected in all cheese samples in freshly made or stored cheese. The results of acid degree value (ADV) showed that all treatments after 15, 30, 40 and 50 days of aging except after one day aging had significant (P<0.05) differences. However treatments D and A had the lowest levels of ADV. The quality property such as composition (moisture content, fat, total nitrogen with dry basis, water soluble nitrogen) was measured. No significant (P>0.05) difference was observed in compositional properties.