مجله علوم و صنایع غذایی ایران
سال سوم شماره 4 (پیاپی 10، زمستان 1385)

Quasi-static compressive tests to determine the mechanical properties of individual brown rice kernels were conducted on whole kernel rice of Hashemi and core specimens of Khazar varieties. The magnitudes of the failure force، failure deformation، breakage energy and apparent elasticity modulus for Hashemi kernels were determined at two moisture content levels، namly، %11 and %17 (w. b.) at four levels of loading rates ranging from 1 mm/min to 5. 5 mm/min. For the Khazar variety، the magnitudes of failure stress and strain، as well as toughness and elasticity modulus were determined at moisture content of %14 (w. b.) for five levels of loading rates ranging from 0. 5 mm/min to 1. 5 mm/min. Statistical analysis of the test results showed that deformation rates had no significant effect on the mechanical properties. Moisture content had a significant effect on all grain mechanical properties. Decreasing moisture content caused significant increases in all these properties. The failure force and the breaking energy for Hashemi kernels increased more than double، when the moisture content decreased from 17% to 11%. The magnitudes of failure force and breaking energy varied from 56 N to 115. 7 N، and from 2. 01 mJ to 5. 23 mJ، respectively. The means of apparent elasticity modulus for compressive test on the core specimens was calculated to be 1. 762 GPa at 17% moisture content and 2. 835 GPa at 11% moisture content. Compressive strength and apparent elasticity modulus for Khazar variety were determined to be 36 MPa and 973. 4 MPa، respectively. Some of the mechanical properties compared well with the published data.

Encapsulation process is a method by which sensitive materials (core) are covered with polymeric materials (wall). As most encapsulation techniques need complicated equipments، long laboratory works and are expensive، therefore، in this study a new technique is utilized for producing microcapsules at a very short time and low cost. This technique is based on the difference between dielectric constants of core and wall materials as well as electromagnetic energy. Edible citric acid crystals (core) were combined with some coating materials such as salab، gum tragacanth، refined starch، sucrose، guar gum، agarose، gelatin، fibrosis carboxymethylcellulose (CMC)، inulin، low and high methoxyl pectin (LMP & HMP)، casein، and sorbitol at ratios about 1:2 up to 1:100 (core: wall). Each mixture was treated up to 600 seconds (depending on the type of wall materials) at various microwave power intensities (10–100 %). Afterwards، the prepared microcapsules were separated by distinct (with defined mesh No.) sieves and their apparent structure and quality were evaluated using binocular and their photographs were taken by a microscope equipped with digital camera. Our findings revealed that amongst the materials were examined only inulin، casein، LMP (9. 5%)، fibrosis CMC، and sorbitol were able to produce high quality as well as highly efficient microcapsules، respectively. In addition، the highest coating efficiency was seen at 100% microwave power intensity (1200W) at 1:10 mixing ratio. Moreover، the optimum microwave treating time for casein، inulin، fibrosis CMC، LMP (9. 5%)، and sorbitol was 400، 75، 400، 100، and 100 seconds، respectively.

Sausages and bologna are heated meat products and they are one of the most popular meat products in Iran. Detection of misuse of non edible animal tissues like visceral organs in quality control and assessment of nutritional value of sausages and bologna is very important. In this study 150 samples of different kind of sausages and bologna in 5 groups according to the percentage of meat content produced with standard beef meat and suitable raw materials in good manufacturing practices. In the lab amount of hydroxyproilne، collagen، total protein، free collagen protein، ratio of collagen on total protein and collagen on free collagen protein of samples assigned and laboratory data analyzed for each group. According to the results، amount of above factors in each group of products can use as a quantitative index for quality control of sausages and bologna.

Adequate calcium (Ca) intake during the crucial growing years maximizes peak bone mass and thus delays the onset of osteoporosis later in life. In addition، Ca plays a protective role against essential hypertension and colorectal cancer. Dairy products، a naturally rich Ca source، are the major source of Ca in our diet. However many people avoid consuming milk، because of economical problems and who are lactose intolerant. For these people، Cafortified nondairy foods can be a significant source of Ca. A number of foods، including bread، staple food، can be fortified with Ca. In this study، formulation and production of fortified Barbari bread with different Ca sources was investigated. In order to، different kind of Barbari breads were prepared with flour fortified with two food-grade inorganic Ca sources such as Ca carbonate and Ca sulfate. Ca was added to flour at two levels: 500 and 1000 mg/ 100 g of flour. one bread was also prepared using ordinary flour. Results of Farinograph and Extensograph tests indicated strength of dough. Results of Farinograph test indicated that the percent of absorbed water، dough development time، dough stability and valorimeter value will increase by adding Ca، while the degree of dough softening in 10 and 20 minates، will reduce. Also atomic absorption spectrophotometry test showed that retaining of Ca in breads was significant (P< 0. 01). CaCO3 and CaSO4 are preffered sources of Ca for the fortification of cereal-based foods as they had no adverse affect on bread quality but CaCO3 is higher in Ca than CaSO4. It is also less expensive. For these reasons، Ca carbonate is a preffered Ca source for fortifying bread.

Food –borne diseases are important public health problems in the world. In recent years significant increase in the incidence of Salmonellas has been reported by WHO. Because Salmonellas resistance to antibiotics. The present study is to evaluate the prevalence of Salmonella in trails chicken meats in Tehran. Between Bahman 2004 to Aban 2005 we analyzed 198 samples of chicken meats in Tehran city. Each sample weighing approximately 800 g was collected. Salmonellas was isolated from 93 of the samples analyzed (47%). The predominant serotypes were S. Enteritis (48. 4%)، S. Hadar (26. 9%) and B4 22. 3%). Otherserotypes such as S. Derby and Paratyphoid B were in much lower levels.

Although Lamiaceae family have been used for centuries as flavouring agent or spice in different foods and also in traditional medicine for treatment of digestive and viral diseases، for example utilization of Ziziphora clinopodioides in yoghurt for above mentioned objectives but a few studies have been performed on the interaction between these compounds and yoghurt starter culture activity. This study was designed to evaluate the effect of Ziziphora clinopodioides on growth of yoghurt starter culture. Trials of set yoghurt were prepared according to standard method with different cocentrations of the essential oil (0،125،250،500 μg/L) and extract (0،1000،2000،4000 μg/L) of Ziziphora clinopodioides. Viability of starter culture was investigated during the storage of yoghurt at 4 ° C at different time intervals. The results showed that the number of starter culture in all samples decreased during storage. There was no significant difference of Ziziphora clinopodioides essential oil between samples and control (P <0. 01). The extract of Ziziphora clinopodioides at high concentration (4000 μg/L) significantly (P <0. 01) decreased the viability of starter culture after 19 th day of yoghurt production.

One of the well known methods for monitoring raw milk bacterial quality، is to determine total bacterial count (TBC)، which has a particular interest to the farmers and processors. Standard plate count (SPC) can be used as a method for determining bacterial load of raw milk. Evaluation of TBC of raw milk on-farm level by using SPC was the main objective of this research. Seven farms were selected randomly and microbiological quality of fresh raw milk was monitored in different steps such as: before and after removal of first part of removed raw milk and also bulk milk that was collected in storage tank. The results showed that removing of contaminated milk from teat chanal has a distinct effect on reduction of bacterial count in fresh milk but it is more important to segregate different grade of raw milk in storage step، due to high bacterial count of mixed raw milk in bulk tank. It can be concluded that microbiological quality of raw milk produced by those farmers was inferior and it is recommended that training and guidance should be given to them.

The aim of this research was to study the effects of whey protein concentrate (WPC) and casein hydrolysate (CH) on chemical (pH and titratable acidity)، physical (consistency and syneresis) and sensory properties of yogurt. Reconstituted skim milk at 10% total solids was fortified with 1 and 2% of WPC، CH and blend of them (WPC to CH ratios of 1:1). For comparison، reconstituted skim milks were made with 11 and 12% total solids as control. Yogurts were prepared with commercial starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and their fermentation proccess were stopped at pH=4. 6 and samples stored at 4°C up to 21 days. The lowest pH value was obtained when milk base was supplemented with WPC. pH values of all yogurt samples did not change significantly during 21 days of storage and ~0. 18% increase in titratable acidity was observed during storage period. The lowest syneresis was observed in yogurts containing blend of WPC and CH. Moreover، the syneresis values of these yogurts increased slower than other samples during storage. Consistency of fortified yogurts was higher than control yogurt and the consistency values of these samples reduced slower than control sample during 21 days of storage. With regards to total acceptability، the best samples were yogurts supplemented with blend of WPC and CH.