MICROBIOLOGICAL QUALITY OF THE DAIRY PRODUCT PEDHA AND ITS IMPROVEMENT USING GAMMA RADIATION

Eighteen pedha samples procured from A and B grade retail shops were examined for their overall microbiological quality and for the presence of foodborne pathogens viz. Staphylococcus aureus, Salmonella sp., Coliforms , Listeria monocytogenes, Yersinia enterocolitica and Bacillus cereus. The microbiological quality of pedha samples from B grade shops was very poor as compared to pedha from A grade shop as evidenced by the very high total bacterial counts (6 × 10⁷ cfu/g), high counts of S. aureus (as high as 7 × 10⁶ cfu/g) and presence of coliforms and Listeria and Yersinia sp. in 33% of the samples. All the samples from A grade shops were also positive for S. aureus though negative for coliforms , Yersinia, Salmonella, Listeria and B. cereus. Gamma irradiation of pedha at a dose of 3kGy at 0C reduced overall bacterial load by five log cycles and S. aureus and coliforms could be totally eliminated. However, 5 kGy dose was necessary to eliminate S. aureus if the initial number exceed 1 × 10⁵ cfu/g. Inoculated pack studies confirmed that 3 kGy dose was sufficient for the complete elimination of up to 1 × 10⁵ cfu/g of S. aureus. A dose of 3 kGy had minimal effect on the sensory quality of pedha and even pedha samples irradiated at 5 kGy dose were acceptable. Treatment with 3 kGy dose of gamma radiation totally eliminated S. aureus and coliforms in pedha, thereby ensuring their microbial safety.     

DIFFERENCES IN THE STRUCTURAL RESPONSE OF 'GRANNY-SMITH' APPLES UNDER MECHANICAL IMPACT AND COMPRESSION

Apple fruits, cv. Granny Smith, were subjected to mechanical impact and compression loads utilizing a steel rod with a spherical tip 19 mm diameter, 50.6 g mass. Energies applied were low enough to produce enzymatic reaction: 0.0120 J for impact, and 0.0199 J for compression. Bruised material was cut and examined with a transmission electron microscope. In both compression and impact, bruises showed a central region located in the flesh parenchyma, at a distance that approximately equalled the indentor tip radius. The parenchyma cells of this region were more altered than cells from the epidermis and hypodermis. Tissues under compression presented numerous deformed parenchyma cells with broken tonoplasts and tissue degradation as predicted by several investigators. The impacted cells supported different kinds of stresses than compressed cells, resulting in the formation of intensive vesiculation, either in the vacuole or in the middle lamella region between cell walls of adjacent cells.     

Effect of the addition of trisodium citrate and calcium chloride during salting on the rheological and textural properties of Cheddar-style cheese during ripening

The effect of addition of trisodium citrate (TSC) and calcium chloride (CaCl₂) on the textural and rheological properties of Cheddar-style cheese was investigated. Cheese curds were salted (2.5%) with NaCl (control) or NaCl supplemented with either TSC or CaCl₂ with a constant ionic strength. Casein-bound calcium phosphate decreased upon addition of TSC and increased upon addition of CaCl₂. Addition of CaCl₂ resulted in increased hardness. Addition of TSC resulted in reduced hardness but more elastic cheeses at high temperatures. The addition of TSC or CaCl₂ at salting had a significant effect on cheese rheology and texture.     

Fruit composition and ripening of Pinot Noir (Vitis vinifera L.) in relation to leaf area

Fruit development from pea size to maturity was investigated in grape berries on fruit-bearing cuttings subjected to a range of leaf removal treatments. Pot-grown vines were trained as a single shoot, with four basal leaves retained. From this point four treatments were applied: 100% leaves retained (control); 66% leaves retained; 33% leaves retained; 0% leaves retained. Leaves were removed as they appeared. The fruit of all treatments passed through veraison, accumulated water, coloured and displayed the typical double sigmoid change in volume, but the onset of growth and colour development associated with ripening was delayed by up to 25 days when leaves were removed. Berry dry weight, sugar content and soluble solids were more affected by leaf removal than berry volume or fresh weight. Bunches from the 0% leaf retained treatment formed seed, but increased very little in dry weight or soluble solids during the course of sampling. This indicates that seed growth and development are independent of sugar accumulation in pericarp tissues.     

Spray‐drying for the production of dried cultures

This review emphasises the importance of spray‐drying as an under‐used but promising technique to preserve viable and active starter cultures and also, potentially, probiotic cultures. The knowledge concerning the production of spray‐dried starter cultures is discussed. Different drying techniques and micro‐organisms have been investigated for their survival through the drying process. During drying and subsequent storage in the dried state, bacteria are subjected to several stresses, which have already been described as causing damage to cells, leading to the loss of cellular viability and activity. Some studies found that several factors/strategies can confer improved cellular viability.     

Kinetics of the Early Hydration of Tricalcium Aluminate in Solutions Containing Calcium Sulfate

The rates of reaction of 3CaO. Al₂O₃, in sulfate-containing solutions of three compositions were investigated. It was observed that the rates of calcium and sulfate uptake decreased with increasing calcium hydroxide concentration. In a further experiment using a calcium sulfate solution, which also contained NaOH, it was established that the kinetics of calcium sulfoaluminate hydrate formation are strongly dependent on the hydroxyl ion concentration. The rate of sulfate ion consumption per unit surface area of 3CaO·Al₂O₃ was observed to be constant during the period in which a calcium sulfoaluminate hydrate is a reaction product. The ratio of calcium-to-sulfate ions consumed in the hydration reactions investigated exceeded unity suggesting the formation of 4CaO·Al₂O₃· n H₂O in addition to ettringite.     

HEAT-INDUCED CHANGES IN EXTRACTABILITY OF BEEF MUSCLE COLLAGEN

Alterations in the extractability of collagen due to heating of beef muscle were determined and compared with shear and penetrometer values. Strips were heated in a water bath programmed to reproduce the internal temperature curve of a roast in a 163°C oven. Samples were removed at internal temperatures of 58, 67, 75 and 82° C. Data were collected on weight of raw and heated meat, amount of juice expressed during heating, moisture, fat and nitrogen content of the meat and juice, total and extractable collagen, and shear force and depth of penetrometer penetration. Solubilized collagen in the heated meat was determined by extraction with water at 40°C. The amount of soluble collagen increased with increasing internal temperature. Comparison of the solubilized collagen data with shear and penetrometer readings suggested that the changes in the contractile fibers influenced texture more than did the changes in the collagen of these muscles under these heating conditions.     

ClassBench: a Framework for Automated Class Testing

In contrast to the explosion of activity in object-oriented design and programming, little attention has been given to object testing. We present a novel approach to automated testing designed especially for collection classes. In the ClassBench methodology, a testgraph partially models the states and transitions of the Class-Under-Test (CUT) state/transition graph. To determine the expected behavior for the test cases generated from the testgraph, the tester develops an oracle class, providing essentially the same operations as the CUT but supporting only the testgraph states and transitions. Surprisingly thorough testing is achievable with simple testgraphs and oracles. The ClassBench framework supports the tester by providing a testgraph editor, automated testgraph traversal, and a variety of utility classes. Test suites can be easily configured for regression testing–where many test cases are run–and debugging–where a few test cases are selected to isolate the bug. We present the ClassBench methodology and framework in detail, illustrated on both simple examples and on test suites from commercial collection class libraries. © 1997 John Wiley & Sons, Ltd.