Beef muscle osmotic pressure as assessed by differential scanning calorimetry (DSC)

Osmotic pressure, an important physiological characteristic of plant and animal tissues, is difficult to measure, and no convenient and efficient method is so far available. In the present work we developed a differential scanning calorimetry (DSC) method, and estimated the physiological osmotic pressure of intact bovine muscle and post-mortem variation during the conversion of muscle into meat. We also examined the major role of sample pH in this variation. This method, based on the determination of the melting onset point of frozen muscle's indigenous water, was compared to a freezing point osmometric method and a soaking method. It was concluded that the DSC method appeared more practical and reliable than other methods and could be applied to various animal and plant tissues and fluids.     

Properties of Soda Aluminosilicate Glasses: II, Internal Friction

Internal friction measurements of soda aluminosilicate glasses, the physical properties of which were reported in Part I of this series, are discussed. The low- and intermediate-temperature internal friction peaks were studied in detail and are shown to be due to the stress-controlled movement of the sodium and nonbridging oxygen ions, respectively. A close correlation was found between the temperature shift of the low-temperature peak and the activation energy for electrical conduction in the soda aluminosilicate glasses. The magnitude of the low-temperature peak was found to depend more on the structural environment of the sodium ions than on the actual soda content. Changes in the intermediate-temperature peak are explained on the basis of the structural model proposed for these glasses.     

北京城市空间发展和土地利用—伦敦经验启示

Beijing is facing a huge challenge to manage the growth of its built-up area whilst also retaining both productive arable land and land for conservation purposes in order to simultaneously realize the three aims of economic development, protecting arable land and generating environmental improvements. Meanwhile, London, as a world city with more than 200 years of industrialization and urbanization, has accumulated rich theoretical and practical experiences for land use planning in a major urban area, such as the creation of Garden Cities, a designated Green Belt and New Towns. This paper firstly analyzes the main characteristics of the spatial distribution of the built-up area, arable land and conservation land in Beijing. Then, some of the key aspects of urban fringe planning in the London region are examined. Lastly, several implications from the experience of London are provided with respect to land-use planning for Beijing, concentrating on a re-appraisal of land-use functions around Beijing, measures to improve the green belt, the development of small towns to house rural-urban migrants and urban overspill, and effective implementation of land-use planning.     

Gas exchange in modified atmosphere packaging. 2: Experimental results with strawberries

Strawberries were used to test a new model describing gas transport through micro-perforated polypropylene films and fruit respiration involved in modified atmosphere packaging. Some experiments were conducted with empty packs initially filled with either 100% N₂ or 100% O₂. Simulations agreed very well with experiments only if we replaced the cross-sectional area of the micro-perforations by areas of approximately half the actual areas in order to account for the resistance of air around the perforations. It is also possible to fit the model to gas concentration changes in packs filled with strawberries, although deviations have been due to the contamination of strawberries by fungi. the model was used to quantify the consequences of the variability of pack properties (number of micro-perforations per pack and cross-sectional area of these perforations) on equilibrium gas concentrations and to define minimum homogeneity requirements for modified atmosphere packaging.     

EFFECT OF SOY PROTEIN ISOLATE AND SOY FIBER ON COLOR, PHYSICAL AND SENSORY CHARACTERISTICS OF BAKED PRODUCTS

Quick breads were formulated to contain 0%, 40%, 50% or 60% Soy Protein Isolate and Fiber (SPI/Fiber), and yeast breads were formulated to contain 0%, 14%, 21% or 28% SPI/Fiber replacement for wheat flour. Physical and sensory data were collected. As SPI/fiber level increased, muffin batter specific gravity, baked product air cell number, Instron peak force to compress by 75%, a value, beany flavor, grain-like flavor, aftertaste, moistness and denseness increased while muffin peak height at the crown, baked volume, L and b values, hue angle, sweetness and crumbliness decreased. There were significant negative correlations between increased level of SPI/fiber in muffins and acceptability of flavor and texture, as well as willingness to purchase or purchase the product at a higher price. As SPI/fiber level increased, bread dough pH after fermentation, air cell number, Instron peak force to compress by 75%, a and b values, beany flavor, grain-like flavor, and aftertaste increased while loaf volume, peak height at the crown, L value, hue angle, cohesiveness and crumbliness decreased. There were significant negative correlation coefficients between level of SPI/fiber and acceptability of flavor and texture, as well as willingness to purchase the product or to purchase it at a higher price.     

Developments in membrane technology

Reverse osmosis and ultrafiltration of whey are commercially successful techniques for adding value to whey. Advances in membrane performance and plant configuration have improved the efficiency of reverse osmosis for whey concentration to a level significantly greater than that of conventional evaporation. Ultrafiltration of whey k also well proven and can provide a range of protein products of diverse composition and functionality.     

Sensory properties of low fat cheddar cheese:effect of salt content and adjunct culture

The influence of salt concentration and of direct-to-vat culture adjuncts (DVCA) on the sensory properties of low fat hard cheese of the cheddar type has been investigated. Salt content has a major influence, and, at a level of 1·8%, low fat cheese with high levels of cheddar flavour and low bitter scores was produced. In addition, further enhancement of flavour was achieved by use of DVCA. Using the methodology described in this report, low fat cheese was manufactured which corresponded in flavour level and balance to that of commercial mature full fat cheese. Nevertheless, textural differences between low fat and full fat product remain to be resolved.     

Effect of Phytic Acid on the In-Vitro Rate of Digestibility of Rapeseed Protein and Amino Acids

Phytic acid in rapeseed flour was reduced by pH adjustment to 5.15 with subsequent dialysis or by phytase treatment at pH 5.15 with subsequent dialysis. The effect of phytate reduction on the rate and extent of protein and amino acid digestibilities was then determined using an in vitro pepsin-pancreatin proteolysis method with simultaneous dialysis of reaction products. A 51% reduction in phytic acid increased the rate of release of many essential amino acids but a further 89% reduction in phytic acid did not enhance that effect. Phytate removal did not improve the protein digestibility.     

Effect of Acetylation on Composition of Phenolic Acids and Proteolysis of Rapeseed Flour

Rapeseed flour was treated with various levels of acetic anhydride to produce flours with 35, 70, and 90% of the ε-amino groups of lysine acetylated. With the extent of acetylation, free phenolic acids ranged from 86 to 35 mg/100g, phenolic acids from hydrolyzed esters ranged from 1.51 to 340 mg/100g, and no insoluble-bound phenolic acid was found. With the extent of acetylation, an increase in rapeseed flour was less susceptible to tryptic and peptic hydrolysis and an increament of water- soluble protein fragments corresponding to molecular weights of 3700–4500 and 1600–2100 daltons was observed. However, these peptides were devoid of phenolic constituents. Acetylated rapeseed flours were less susceptible to tryptic and peptic hydrolysis.