Showing 7 results for SHahidi
A.r. Sadeghi Mahounack, F. Shahidi,
Volume 5, Issue 1 (spring 2001)
Abstract
The antifungal effect of sodium diacetate on inhibiting the growth of some bread spoiling molds was examined both in culture media and in flat bread “In situ”. In the first step, the antifungal effect of different concentrations of sodium diacetate: 0, 1000, 2000, 3000, 4000, and 5000 ppm were examined against Aspergillus sp., Aspergillus niger, Rhizopus sp., and Penicillium sp.
The results indicated that as the concentration of sodium diacetate increased, the mold growth decreased. At 5000 ppm the mold growth was inhibited up to fifth day (the last day of experiment). Based on these results, the antifungal effect of different concentrations of sodium diacetate was evaluated in bread “In situ”. In this stage Aspergillus sp. was selected as the indicator mold. The results indicated that if 3000 ppm of sodium diacetate is used, not only mold growth is inhibited but bread staling can also be prevented. This concentration of sodium diacetate does not have any harmful effect on texture and flavour, and can increase bread shelf life up to four days. Higher concentrations of sodium diacetate can inhibit mold growth completely, but have negative effects on texture and flavour. Therefore, 3000 ppm of sodium diacetate is recommended for increasing bread shelf life.
A. H. Elahami Rad, F. Shahidi,
Volume 8, Issue 1 (spring 2004)
Abstract
Bulk tomato paste is produced in concentrations higher than 35% (350 Brix scale) and its packaging is not hermetic. In recent years, the production of this product in our country has considerably increased. One of the most important problems in the tomato paste industry of Iran is the preservation of bulk tomato paste. Shelf-life of tomato paste depends on many factors such as initial quality of tomato paste, cooling conditions, salting, packaging, handling, and cold storage. The product factors evaluated in this study included: 1) microbial parameters such as total count, acid-resistant microorganisms, and Howard Mould Count and 2) physico-chemical parameters such as acidity, pH, amount of lactic acid (D and L forms), and total dry matter.
Experimental data showed that using high brix (35-38) in producing tomato paste along with salting the product surface and storing it at 0 ºC had only a limiting effect on microbial changes and could not prevent their growth completely. However, salting treatment had a great effect on surface growth of fungi and their ability to produce colonies and mycelia. On the basis of the results obtained from this study, cooling of bulk tomato paste in ambient temperature is critical to bulk tomato paste production process and also has an important effect on the quality and shelf-life of the product.
A. Sadeghi, F. Shahidi, S.a. Mortazavi, M. N. Mahalati, S.h.r. Beheshti,
Volume 12, Issue 43 (spring 2008)
Abstract
The aim of this study was to use Alpha-amylase termamyl 2-x for maltodextrin production from corn starch and evaluate its industrial uses. Based on the results obtained in laboratory, this process was accomplished in pilot plant scale. The process included preparation of starch suspension, pH adjustment, addition of enzyme, heating under stirring, continuous control of DE and Brix, enzyme inactivation in adequate DE, separation of soluble sections by centrifuge and finally spray-drying of the maltodextrin liquid. In this investigation, the amount of DE at dry matter was calculated under three enzyme concentrations (0.2, 0.25 and 0.3 ml of Alpha-amylase termamyl 2-x per Kg of starch) and in three different hydrolysis temperatures (60, 65 and 70 ºC) at constant pH (6). A completely randomized design with factorial arrangement and 5 replications was conducted. To study the relationship between DE and different parameters, multiple linear regression was used. Finally, for approximation of DE (based on enzyme concentrations, temperatures and hydrolysis times) a regression model was used. The results from different enzyme dosages at the same temperature and time of hydrolysis differed significantly (p≤ 0.05). Meanwhile, the best enzyme concentration and hydrolysis temperature for maltodextrin (high DE) production after 300 minutes were 0.25 ml of enzyme per kg of starch and 70 ºC, respectively. In these conditions, the least residual starch concentration and residual Alpha-amylase activity were observed.
A Kochaki, A Sadeghi, F Shahidi, A Mortazavi, M Nasiri,
Volume 13, Issue 47 (fall 2009)
Abstract
This study was intended to use the sourdough LAB containing specific starter cultures for Barbari bread production and reduction of its staling. For sourdough preparation, fresh microbial cells were collected by centrifugation from LAB cultures. Then 1.5% of flour (w/w) from these washed cells with the same amounts of wheat flour and tap water and 0.25% (w/w) active dry yeast extract, containing Saccharomyces cerevisiae were mixed. The effects of fermentation time (8, 16 and 24 hours), fermentation temperature (28, 32 and 36 ºC) and type of starter culture (Lactobacillus sanfransicencis, Lactobacillus plantarum and a mixture of both LAB) were analyzed in a completely randomized design with factorial experiment with 4 replications. Bread staling was determined by its measuring crumb hardness and specific volume in 1, 24, 48 and 72 hours after baking. Correlation between variables was obtained by multivariate regression, and regression models were exhibited. The results showed that sourdough had significant effect (p≤0.05) on reduction of Barbari bread staling at 1, 24, 48 and 72 hours after baking in comparison with control sample. Moreover, the sample prepared with Lactobacillus plantarum (24 h fermentation time and 32 ºC fermentation temperature) had the maximum specific volume and the least staling, 72 hours after baking.
M Bolandi, F Shahidi, N Sedaghat, R Farhosh, R Ghasemzadeh,
Volume 13, Issue 47 (fall 2009)
Abstract
Saffron is one of the most important crops in Iran and the quality of its dried stigma is highly depended on the processing and storage conditions. In this study, the effect of different storage conditions in terms of temperature (20, 30 and 40°C) and water activity (0.32, 0.52 and 0.75) during 12 weeks storage on color strength, aroma and bitterness of saffron were investigated. In order to study of moisture (water activity) different saturated solution of MgCl2, Mg(NO3)2, MgBr2 and NaCl in the various temperatures were used. Results showed the color strength decreased as temperature increased. Increasing of water activity resulted in deterioration of crocin and consequently decreasing of color. Furthermore, after 12 weeks of storage, the color strength had a noticeable decrease, the bitterness also decreased but the aroma increased.
H Baghaee, F Shahidi, M.j Vriadi, M Nasiri Mahalati,
Volume 13, Issue 47 (fall 2009)
Abstract
Cantaloupe (Cucumis melo L.) is one of the most important melons in Iran especially in Khorasan province. The cantaloupe seed is a good functional and nutritional source for human, having large amounts of essential amino acids and unsaturated fatty acids. In spite of nutritional and functional aspects, it does not have considerable applications in food industry yet. Cantaloupe seed milk's pH is about 6.8, so cannot be stored for a long time. In this work, pH of cantaloupe seed milk decreases to 4.15 in 3 treatments (citric acid, orange concentrate, and orange sacs) and a constant amount of lemon juice. At first, nutritive value of seed milk was measured. According to results, this milk is a good source of protein (1.52%), phosphorus (41/3 ppm) and potassium (17 ppm). After that, storage stability of cantaloupe seed beverage at refrigerator temperature (4 °C) for 42 days was evaluated by analyzing changes in the chemical, microbial and sensory properties. The results showed that the orange concentrate-cantaloupe seed beverage reached the highest score of total acceptance (3.67 on a 5-point hedonic scale). In these conditions, we couldn’t find any molds and yeasts in the samples, thus the shelf life of the mentioned beverage could be 6 weeks at 4 °C.
N Vahedi, M Mazaheri Tehrani, F Shahidi,
Volume 13, Issue 48 (fall 2009)
Abstract
In this study, the effect of “Osmodehydrofrozen” fruit addition on sensory, physical, chemical and microbiological properties of concentrated yoghurt and its quality during storage was evaluated. This research was done in two stages. At the first stage, fruit percentage, type and addition time (before and after fermentation) was determined. The results indicated yoghurts containing 10% apple or 13% strawberry, which was added before fermentation had a better quality. Because of high osmotic activity of apple, the synersis was lower in apple yoghurt in comparison with strawberry yoghurt. According to osmotic activity of both fruits, the synersis value was much lower than that of fruit yoghurts, which contained untreated fruits. Taste value was higher in strawberry yoghurt and texture and mouth feel values were higher at low percentages of fruit. The results of the second stage (quality evaluation during storage) indicated that storage had a significant effect on pH, acidity, synersis, taste and texture (P<0.05). In samples which contained apple, coli forms disappeared after 7 days of storage. In samples that contained strawberry, coli forms disappeared after 7 days of storage.
