NMR IMAGING, CALORIMETRIC, and MATHEMATICAL MODELING STUDIES of FOOD FREEZING

Nuclear magnetic resonance imaging (MRI), calorimetry, and temperature measurements were used to monitor cylindrical potato sections frozen at -11C and -42C. MRI showed the advance of the nonsymmetric freezing zone and loss of signal intensity as liquid water turned to ice. Differential calorimetry was used to follow heat removal during transient freezing. Measured times to 95% enthalpy change were 24 min (-42C) and 49 min (-11C), as compared to modeled values of 29 min (-42C) and 100 min (-11C). Times to 95% change in the NMR signal, integrated over the area of the image, were 21 min (-42C) and 56 min (-11C). Changes in NMR signal intensity could be correlated with the amount of unfrozen water remaining after a steady-state had been reached. At -42C, NMR indicated 25% unfrozen water remaining as compared to 26% by calorimetry, and 22% by modeling. At -11C, NMR measured 67% unfrozen water remaining as compared to 48% by calorimetry, and 25% by equilibrium modeling.     

Performance of Layout Algorithms: Comprehension, not Computation

Many algorithms address the problem of rendering an abstract graph structure as a diagram in as efficient and as elegant a manner as possible. The criteria for judging the worth of these algorithms are typically the extent to which they conform to common aesthetic criteria (e.g. minimising the number of crossings, maximising symmetry), or their computational efficiency. The algorithms are not usually judged on their ability to produce diagrams that maximise humans’ performance on tasks which require their use.This paper presents an example experimental methodology for considering the relative worth of eight layout algorithms with respect to human performance, together with details of an experiment using a single graph. The results indicate that, with the exception of one algorithm, there is no statistical difference between the performance data of the algorithms when applied to this graph, indicating that they produce drawings of comparable difficulty. This result is despite the different aesthetic bases for the algorithms.     

THE SOLUBILITY OF PARAFFINIC HYDROCARBONS AND THEIR DERIVATIVES IN SUPERCRITICAL CARBON DIOXIDE

The solubilities of twenty-five paraffinic model compounds, octadecane (C₁₈H₃₈) through tetracosane (C₂₄H₅₀) and related monofunctional derivatives, were measured in supercritical carbon dioxide at 310 and 320 K. The derivatives included sulfides, amines, phosphines, ketones and other functional groups. Several of the solutes were liquids at the extraction temperatures and pressures, and both liquid and fluid phase binary composition data are reported in some cases. A systematic attempt was made to explore how the presence of a particular functional group on the solute molecule affected the solubility of the compound relative to the parent hydrocarbon of equivalent chain length.     

Effect of Blanching and Drying on Pectin Constitutents and Related Characteristics of Dehydrated Peaches

The effects of sulfuring, blanching, dehydration, and storage (of dehydrated fruits), on the pectic constitutents and other characteristics of peaches are reported. Adequate blanching stabilized pectins of the dehydrated peaches so higher rehydration capacity and lower rehydration losses were observed after 5 min blanching. Increase in degradation was observed in nonblanched or 1.5 min heat-treated fruits, which resulted in lower rehydration capacity. A significant correlation was found between the contents of total pectin and protopectin fractions and the firmness or rehydration ratio of the peaches. Thus, pectin, one of the major cell-wall and intercellular tissue components, plays a significant role in determining the textural-structural characteristics of dehydrated fruits.     

Haze Development in Aerobically or Anaerobically Produced Clarified Apple Juices

Haze production in aerobically or anaerobically produced Red Delicious apple juice was assessed following heating, aeration, and protein addition. Stored aerobic juice produced haze in 6 wk, but anaerobic juice was haze-free unless oxygen was introduced. Phenolic material was incorporated into haze in both systems. HPLC (detection at 420 nm) of concentrated juice and addition of 100 mg/L BSA suggested the presence in both juices of ‘reactive’ material which could complex and precipitate during storage. Phenolic compounds, heating, and especially oxidation during processing (and storage) appear to be major determinants of ‘haze potential’ in clarified apple juice.     

Corrosion of a Borosilicate Glass by Orthophosphoric Acid

A borosilicate glass was resistant to orthophosphoric acid at 95°C, whereas considerable corrosion occurred at higher temperatures. Tenacious crystal formation provided a barrier against further attack, but also produced stress resulting in spontaneous glass breakage. The acid-glass reaction is attributed to acid dehydration and consequent transformation to aggressive pyrophosphate.