Aijaz Hussain Soomro

Heat resistance and salt hypersensitivity in Lactococcus lactis due to spontaneous mutation of llmg_1816 (gdpP) induced by high-temperature growth

ABSTRACT During construction of several gene deletion mutants in Lactococcus lactis MG1363 which involved a high-temperature (37.5°C) incubation step, additional spontaneous mutations were observed which resulted in stable heat resistance and in some cases salt-hypersensitive phenotypes. Whole-genome sequencing of one strain which was both heat resistant and salt hypersensitive, followed by PCR and sequencing of four other mutants which shared these phenotypes, revealed independent mutations in llmg_1816 in all cases. This gene encodes a membrane-bound stress signaling protein of the GdpP family, members of which exhibit cyclic dimeric AMP (c-di-AMP)-specific phosphodiesterase activity. Mutations were predicted to lead to single amino acid substitutions or protein truncations. An independent llmg_1816 mutant (Δ1816), created using a suicide vector, also displayed heat resistance and salt hypersensitivity phenotypes which could be restored to wild-type levels following plasmid excision. L. lactis Δ1816 also displayed improved growth in response to sublethal concentrations of penicillin G. High-temperature incubation of a wild-type industrial L. lactis strain also resulted in spontaneous mutation of llmg_1816 and heat-resistant and salt-hypersensitive phenotypes, suggesting that this is not a strain-specific phenomenon and that it is independent of a plasmid integration event. Acidification of milk by the llmg_1816-altered strain was inhibited by lower salt concentrations than the parent strain. This study demonstrates that spontaneous mutations can occur during high-temperature growth of L. lactis and that inactivation of llmg_1816 leads to temperature resistance and salt hypersensitivity.

Characterization of Auricularia auricula polysaccharides and its antioxidant properties in fresh and pickled product

The study planned to determine proximate composition, antioxidant activity and chemical characterization in the fruit bodies of Auricularia auricula and pickled product. Two polysaccharide fractions (AAPF, AAPP) were purified from the fruiting body of A. auricula by ethanol precipitation, deproteination and macroporous resins and were subsequently lyophilized. The results showed that AAPF consisted of five monosaccharides, including glucose, rhamnose, arabinose, mannose and galactose with a molar ratio of 16.74:1.0:1.18:1.0:1.0; in contrast, AAPP was composed of four monosaccharides, namely arabinose, mannose, galactose and xylose with the molar ratio of 15.59:1.52:4.76:1.0. AAPF and AAPP were characterized by Fourier Transform Infrared spectroscopy (FTIR), which indicated peaks at approximately 3500cm(-1) and 522.28cm(-1) in the carbohydrate region and composed of β-glycoside linkages at the 1200-1000cm(-1) peaks. However, the antioxidant activity of AAPF demonstrated a significant result in scavenging free radicals except for DDPH. The in vitro test indicated that AAPF and AAPP have good antioxidant activity, demonstrating that A. auricula polysaccharide has immense potential as a functional food.

Selection of yoghurt starter culture from indigenous isolates ofStreptococcus thermophilus andLactobacillus delbrueckii subsp.bulgaricus on the basis of technological properties

The aim of this study was to explore the potential of indigenous strains ofLactobacillus delbrueckii subsp,bulgaricus andStreptococcus thermophilus as yoghurt starter culture, for this purpose some important technological properties were studied. The strains ofLactobacillus delbrueckii subsp.bulgaricus Lb5, Lb7, andStreptococcus thermophilus St4 and St7, produced more than 0.7% acidity after 6h of incubation in skim milk media. The acetaldehyde was detected as major aroma compound produced by mixed culture M1 (Lb5∶St4) i.e., 19.95 ppm at 43°C. Yoghurt was prepared with different combinations of the culture and sensory analysis performed by a trained panel revealed that pleasant yoghurt was prepared with mixed culture ofLactobacillus delbrueckii subsp.bulgaricus Lb5 andS. thermophilus St4. The results suggested that these strains have potential to be used as starters for yoghurt production.

Extent of extraneous water and detection of various adulterants in market milk at Mirpurkhas, Pakistan

In Pakistan, milk adulteration is a growing issue of significant importance. This problem persists at every level; from production point to consumption. Adulteration poses ill effects on the public health. This study was designed to screen the various adulterants in the market milk sold in the vicinity of Mirpurkhas district of Sindh, Pakistan during the year 2013. A total of 100 milk samples were collected. Twenty milk samples (n= 20) from each of milk producers (MP), milk collectors (MC), middlemen (MM), processors (P) and dairy shops (DS) were examined for various adulterants. Among these adulterants water (73%) was found in majority of milk samples, followed by detergent (32%), cane sugar (22%), caustic soda (20%), rice flour (17%), sodium chloride and skimmed milk powder (15%), hydrogen peroxide (13%), starch (12%), formalin (11%), urea and vegetable oil (10%), boric acid (8%), ammonium sulfate (6%), glucose (5%), sorbitol (4%) and arrowroot (1%), respectively. Freezing point of 65% milk samples of MP, 75% of MC, 75% of MM, 80% of P and 85%% of DS appeared towards 0 o C rather than that of control milk, and assumed to be adulterated with extraneous water. The averaged extent of water in milk sold by P remarkably higher than that of other milk marketing channels, but statistically non-significant (P>0.05) with all milk intermediaries; MP, MC, MM and DS. The risk of adulteration at DS was found to be significantly higher (P 0.05) with P and MM.

Removal of Pesticide Residues from Tomato and its Products

Plant protection agents (more commonly known as pesticides) are widely used in agriculture to increase the yield, improve the quality and extend the storage life of food crops. The study was carried out in order to determine the effectiveness of various traditional processing treatments on reducing the residual load of pesticides from tomato and its products. Results showed that lipid soluble pesticides residues were reduced most effectively in sun-drying (90-97%) followed by frying (91-99%) and thermal dehydration (89-90%). The data further indicated that profenofos residues dislodged more effectively than bifenthrin and endosulfan. The least reduction was noticed in endosulfan residues. Similarly in case of water soluble pesticides, the effect of sun-drying, frying and thermal dehydration on reduction of pesticide residues were within the range of 94-97%, 92-96% and 91-96%, respectively. Maximum reduction was found in emamectin benzoate residues followed by imidacloprid and diafenthiuron.

Quality Attributes of Immature Fruit of Different Mango Varieties

The study was carried out to evaluate quality attributes of immature fruits of four commercially grown varieties of mango namely Sindhri, Chaunsa, Langra and Desi. The immature mango fruits were collected from basin of mango tree in the end of April followed by washing, surface drying and extraction of fruit pulp. The extracted fruit pulp was assessed for pH, TSS, moisture and ash percentage, acidity, vitamin C, fat, protein and sugars. Besides, minerals including sodium, calcium, potassium, magnesium, zinc, iron, copper, chromium, and manganese were also determined. On the basis of varietal comparison Sindhri had more moisture (88.60%), ash and fat (0.60%) each, total sugars (6.99%) and reducing sugars (2.78%) as compared to rest of the varieties. However TSS (9.35%), protein (0.71%), and non reducing sugars (4.86%) were recorded the highest in Langra variety. Only the Chaunsa variety had maximum pH of 3.01 and vitamin-C (27.16 mg 100g -1 ). Regarding mineral elements, Desi was found potential in terms of sodium (453.93 mg kg -1 ), calcium (403.79 mg kg -1 ), Zinc (3.47 mg kg -1 ) and iron (5.95 mg kg -1 ). The zinc and iron was at par with the results obtained from Langra. However, potassium (904.58 mg kg -1 ) and copper (2.58 mg kg -1 ) were observed the highest in Langra, magnesium (78.09 mg kg -1 ) in Chaunsa and manganese (2.43 mg kg -1 ) in Sindhri.

Loaf Characteristics and Sensory Properties of whole Wheat Bread Fortified with Sorghum and Rice Flour

Bread is a common staple food in developing countries and also in many other regions of the world. The loaf characteristic and sensory attributes of bread samples prepared by using different composite flours in which ratio of whole wheat flour, sorghum flour and rice flour kept as 100:0:0 (F1), 80:10:10 (F2) and 60:20:20 (F3) was evaluated. The composite flours F1, F2 and F3 were subsequently used for making bread samples i.e. whole wheat bread (WWB), sorghum rice bread-1 (SRB-1) and sorghum rice bread-2 (SRB-2), respectively. The results indicated that significantly higher loaf weight (g) was recorded in SRB-2 followed by SRB-1 and WWB. Significantly higher bread height (cm) was noticed in SRB-1 followed by WWB and SRB-2. The bread sample WWB was found to have significantly higher volume and specific volume followed by SRB-1 and SRB-2. It was also revealed that significantly higher average score for bread crust color was perceived by WWB. However, bread sample SRB-1 perceived significantly higher score (P<0.05) for crumb color, texture, aroma, taste and overall acceptability. It is concluded from present study that fortification of bread with different proportions of rice and sorghum flour was

Occurrence ofListeria monocytogenes in bovine milk in Hyderabad, Pakistan

In the present study 200 milk samples (50 each from cow, buffalo, market and mastitic milk) were collected from Hyderabad. Among the isolated presumptiveListeria spp., all the isolates were identified asListeria monocytogenes and showed a prevalence of 6, 8, 10 and 12%, respectively. Through serotyping analysis all isolates were confirmed asListeria genus, since they agglutinated with polyvalent ‘O’ serum; 12 of the 18L. monocytogenes isolates were ascribed to serotype 1, and 6 to serotype 4. Furthermore, the pathogenicity was investigated in rabbit and mice through Anton and inoculation tests, respectively. The organism produces keratoconjunctivitis in rabbit while it causes death and presence of necrotic foci in liver, spleen and kidneys of mice.Listeria monocytogenes was found sensitive to ampicillin, chloramphenicol, ciprofloxacin, gentamycin and kanamycin.

Effects of xanthan gum on cooking qualities, texture and microstructures of fresh potato instant noodles

In the present investigation, fresh potato instant hot dry noodles were prepared to evaluate the effect of xanthan gum (XG) on cooking qualities, texture and microstructures of noodles. Three types of noodles were prepared with different incorporation level of XG (0.3, 0.6 and 0.9% w/w, wheat flour basis) and their physico-chemical and functional properties in relation to textural and rheological characteristics were evaluated. The results showed that incorporation of 0.60% XG (w/w, wheat flour basis) increased peak viscosity, trough, breakdown, final viscosity, setback increased dramatically, whereas pasting temperature declined compared with control. The addition of XG resulted in increased G′ and G″ and contributed to fast rehydration higher cooking loss, water absorption and increased porosity. The findings in this work provided evidence that XG could be used as a partial additive for wheat flour in non-fried instant noodles production.

Analysis of Nutritional Components of Horse Radish Tree Flowers (Moringa oleifera) Wildly Grown in Sindh Province

The present research study was aimed at determining the proximate and mineral composition of horse radish tree flowers by utilizing standard methodologies. The mean moisture content in fresh, thermally dehydrated, curry, shade dried and boiled fresh /processed samples of horse radish tree flowers was 80.98, 5.40, 68.07, 5.84 and 86.26%, respectively. The vegetable had the highest pH, carbohydrates, total solids, nitrogen free extracts and calorific values in thermally dried samples and crude fiber, ash and protein values were higher in shade dried samples. Whereas, fat and total fatty acids were found higher in curry samples. There was a significant presence of dietary essential micro-nutrients. It was therefore revealed that horse radish tree flowers ( Moringa oleifera ) when consumed in curry form could also be a good source of nutrients. The inclusion of horse radish tree flowers into the diet could potentially address some of the challenges, such as health benefits, food security and increase life expectancy in Sindh, Pakistan.