Journal of Food Biosciences and Technology
Volume:4 Issue: 2, Summer-Autumn 2014

The objectives of this study were to assess the microbiological quality of Egyptian yoghurt and to investigate the antagonistic activity of some probiotic bacteria against some food borne pathogens in vitro and in yoghurt. The results indicated a poor microbiological quality of yoghurt, since the microbiological parameters recorded higher values than the admissible levels. Results from the agar spot test and well diffusion assay showed the capability of probiotic bacteria to inhibit the growth of S. aureus, E. coli O157:H7 and  L. monocytogenes in vitro. Yoghurt produced from milk artificially contaminated with S. aureus (8.48 log cfu mL-1) and E. coli O157:H7 (8.3 log cfu mL-1) was used for studying the ability of L. acidophilus La-5 and B. longum ATCC15707 to inhibit the growth of such pathogens. During the refrigerated storage the counts of both pathogens decreased significantly in the probiotic yoghurt than in control one. Survival of both L. acidophilus La-5 and B. longum ATCC15707 in yoghurt was satisfactory as both bacteria remained viable at levels > 107 cfu g-1 after 15 d of storage at 4 ºC,  which indicate that the yoghurt would be a suitable vehicle for probiotics.

Carotenoids are red, orange and yellow pigments, which are widely distributed in fruit and vegetables. The aim of this research is to investigate the effect of conventional, high pressure and microwave cooking on the concentrations of β-carotene in carrot and sweet corn. Raw carrots were washed, peeled and diced to a uniform size and then frozen at -70°C. Sweet corn was also provided in a similar ready to serve condition and stored at -70°C. β-carotene contents in the vegetables were quantified after extraction and injection onto the High Performance Liquid Chromatography column and measured on the UV-Visible detector. The results indicated the conventional cooking of carrots and microwave cooking of corn for 10 minutes were taken as the ideal cooking procedure to retain this vital important micronutrient. Also microwave cooking for 20 minutes had the highest loss of β-carotene in both carrot (53.76%) and corn (83.03%) as compared to other methods of cooking.

A preliminary study on statistical modelling of a process for depolymerisation of cassava non-starch carbohydrate using halide salt assisted phosphoric and pyruvic acids were accomplished. The effects of three independent variables namely; acid concentration, potassium iodide salt and duration were studied using the central composite rotatable design on hydrolysis of the cassava non-starch carbohydrate. Hydrolysate marker, reducing sugar was evaluated as a measure of depolymerisation, consequently used as response in the study. Equations for predicting the response were developed and adequacy confirmed using analysis of variance and residual assessment. The predictive model provides the potentials of using phosphoric acid and pyruvic acid as depolymerisation agent for cassava non-starch carbohydrate in the presence of potassium iodide salt. This would open a new opportunity for depolymerisation of cassava non-starch carbohydrate that is usually used for low premium animal feed or left as dung resulting to environmental pollution.

Oils and fats are substances that are important nutritionally and have important role and impact on human health. Energy consumption and preservation in respect of food industry and the increase in the world population and search for new sources of oils and fats to full fill the need of the society particulary the nutritional requirements have introduced this research topic. Therefore aim of this work is to underestand the extraction efficiency of the solvents and to evaluate the extracted oil. Hexan and AW406 were employed to evaluate the extraction efficiency at 60, 80 and 100°C for a period of 30 minutes using Soxhlet apparatus as a mean to extract the oil.The extracted oil was subjected to a series of chemical analysis consisting of fatty acid composition, phospholipid concentration, percent nonsaponifiable matter, Induction period measurement, sterol and tocopherol composition and analysis.The result indicated that the solvent AW406 behavior depends on the temperature of extraction and longer period of extraction is required when AW406 is compared to n-hexane.Chemical analysis of the extracted oil indicated that linoleic and oleic acids were the predominant fatty acids present and β-sitosterol and α-tocopherol constituted the majority of the respective fractions. Due to the fact that extracted oil from apple seeds had approximately 89% of their fatty acid in the unsaturated form, mainly linoleic acid followed by oleic acid, the oil might be employed in food and pharmaceutical products.

Desirability and good background of yogurt have led the manufacturers to use this product mostly for producing milk-based probiotic products. The aim of this study was to evalutate the effect of a mixture of prebiotics including oligofructose, lactulose, and inulin on physicochemical properties (pH value, acidity, and syneresis) of synbiotic yogurt containing lactobacillus casei. Pasteurized milk was inoculated with certain amount of starter, prebiotic, and probiotic bacteria, then yogurt samples were prepared, and at 1, 7, 14 and 21 d, pH value, acidity, and syneresis were measured by pHmeter, titration method, and centrifuge, respectively at certain intervals. The results showed that the sample containing the mixture of lactulose, inulin and oligofructose (LIO) had the lowest pH value, highest acidity and syneresis. In contrast, the sample containing lactulose and inulin mixture (LI) had the lowest acidity and syneresis showing a significant difference from the control (probiotic yogurt without prebiotic). The variation trend of acidity and syneresis was rising and the sample containing lactulose and inulin (LI) mixture contained sample was selected as the best synbiotic yogurt sample.

Bleaching process is an essential stage in the refining of vegetable oils and fats. In this process the colour and the primary and secondary oxidation products are removed by the treatment with the acid activated bleaching earth .The aim of this project is to understand the effect of bleaching on the physical characteristics and chemical constituents of neutralized canola and sunflower seed oils. Canola and sunflower seed oils were bleached at 100o C for 30 minutes. The results indicated that there were significant reductions in peroxides and red and yellow colours of the oils. The induction period representing the oil resistance to oxidation was improved however the acidity was increased that might be due to the nature of the acid activated earth that has caused slight hydrolysis. Slight changes in fatty acid composition was observed that was due to the oxidation of poly unsaturated fatty acids namely linoleic acid in both oils. Some reduction in the total non saponifiable matter was observed. This might be due to the oxidation of tocopherols and changes of the sterols structures due to their conversion to steroidal hydrocarbons.

In this research, after carrying out chemical tests measuring the moisture, protein and ash contents on rice flour according to standard methods, gluten- free breads were prepared from rice flour combined with 0.5% Carboxy Methyl Cellulose (CMC) and 1% -κCarrageenan gum. A sample lacking gum was also produced as control. Rice breads (with gum and without gum) were then produced by semi-industrial method. Dough and bread yield assays as well as voltmeter were carried on the obtained breads. The results showed that the addition of two gums led to the improvements of dough and bread yield properties as well as specific volume as compared to the control sample with 1% CMC that resulted in a more specific volume and 1% k-carrageen that gave a better dough and bread yields. Chemical tests measuring the moisture, ash and protein contents were performed on all bread samples followed by the determination of staling rate through instrumental method (Instron machine) according to the standard methods. The results of chemical tests carried on wheat flour and rice flour showed that consumed flour was suitable for toast bread making. The results of chemical tests carried on produced bread sample showed that K2 treatment had the highest moisture content; KC treatment had the most ash content; control treatment 1(W) showed the highest protein followed by KC treatment and rice control treatment (C) had the lowest amount of moisture, ash protein. The results obtained from staling rate test instrumentally at time intervals of 24, 48 and 72 hours after baking showed that at three time intervals C treatment had the highest staling rate, and W, K2 and C2 treatments had the lowest staling rate respectively. The obtained rice breads were presented to a group of panelists to assess the sensory properties including porosity and granular appearance of the bread crumb, aroma, color of crumb, chewiness and texture as well as staling property. The results obtained from the sensory analysis indicated that the addition of two gums led to improvement of sensory properties of gum containing samples as compared to the control- of among gum- containing samples, bread with 1% CMC had the best sensory properties.

Approximately 10-30% of tomatoes are wasted during processing. Tomato pomace consists of crushed skin and seeds of tomatoes. Seeds might be considered as a potential source of vegetable oil. The extracted oil is high in unsaturated fatty acids, namely linoleic acid. The extracted oil after purification or refining might be employed for consumption. The object of this study was to evaluate the extraction yield of tomato seed oil by using ultrasound at different ratios of seed to solvent, temperatures and times variations and compare this method to the percolation procedure. Series of values and chemical components namely unsaponifiable matter, iodine value, saponification value and fatty acid composition, sterol and tocopherol profiles of the extracted oil were determined.

Date Syrup is a natural sweetener that is a suitable ingredient to be used in formulation of food products in order to improve the nutrient properties. In this research a new drink is produced by the addition of date syrup in concentration of 5%, 8%, and 10% to milk. Physical, chemical, rheological and sensory properties of the samples were evaluated. Statistical analysis using SPSS software and Duncan test at 95% confidence level were employed. It was concluded that with increasing the amount of date syrup in the formulation of drink, characteristics such as dry matter, specific gravity, turbidity, were increased. Color measurement of the samples reported that the color parameters, L*, a*and b*, of the samples have a significant difference and using date syrup in formulation of drink caused changes in the color of the samples. Sensory evaluation of the samples also indicated that by increasing the amount of date syrup the acceptability of the samples was increased and the highest score belonged to the sample including %10 date syrup.

Some chemicals used by human such as food additives are mutagenic and mutagenicity effects analysis of them is very important because of considerable consumption by man. One of the most common methods used in the recognition of the chemicals' mutagenicity is Salmonella Typhimurium Reverse Mutation (Ames) test. The purpose of the present study is mutagenicity effects analysis of sodium nitrite, boric acid and various kinds of borax.Bacterial strains in this study are TA98 and TA100 which are derived from Salmonella Typhimurium by creation of several mutations in Histidin operon and their dependency on this chemical; also, by creation of rfa and UVrB mutations and pKM101 plasmid addition. Sodium nitrite, boric acid and three kinds of borax were selected for the test and various dilutions of them were provided. Performing Ames test, revertant colonies average of TA98 and TA100 strains were calculated for each dilution separately as the result of the above chemicals' function; then, according to the achieved A value, dose - response curve was depicted.  The results of present study demonstrate non-mutagenic effects of sodium nitrite, boric acid and three kinds of borax through Ames test, by TA98 and TA100 strains. According to the wide consumption of these food additives in food industry, analysis of their mutagenic effects is very important and we suggest more investigation using different test to approve the results.