Leakage of Anthocyanins from Skin of Thawed, Frozen Highbush Blueberries (Vaccinium corymbosum L.)

Factors affecting the tendency of thawed blueberries to leak pigmented exudate were investigated. Drip and anthocyanin leakage rates (ALR) were determined spectrophotometrically. Leakage vs time curves were linear or two-phase linear, ALR varying with cultivar, ripeness, and berry condition. Dewaxing increased ALR with most cultivars. ALR did not correlate with berry anthocyanin content, surface area, or cuticle thickness. ALR and amount of drip were poorly correlated. ALR varied from berry-to-berry within samples. Leakage was observed to be nonuniform on berry surfaces, appearing at skin cracks and ruptures, the calyx area, and other point sources. An hypothesis relating leakage to skin condition, fluid accumulation, and anthocyanin content is presented.     

Efficiency in public schools: a case study in non-parametric measurement

This study illustrates the problem of efficiency measurement in stochastic input-output systems when market price data are unavailable. Efficiency comparisons by non-parametric methods are attempted for selected public elementary schools in California for 1976-77 and 1977-78. A suitable linear programming model is developed for the efficiency frontier in the input-output space, which is found to be significantly different from an average relation. This is shown to have important policy implications for improving input performance for better efficiency.     

Sweetness of α-, β-, and Equilibrium Lactose Relative to Sucrose

The sweetness of α-, β-, and equilibrium lactose, measured by a trained panel using paired comparison with standard reference solutions of sucrose of concentrations from 0.50–6.50%, ranged from 30–35% that of sucrose. The sweetness of β-lactose was 105–122% that of α-lactose. The predicted swweetness of lactose at mutarotation equilibrium, calculated from sweetness values for α- and β-lactose and from the relative amounts present as determined by polarimetry, i.e., 38%α and 62%β, did not differ significantly from the experimentally determined sweetness value, indicating an absence of synergism for sweetness in mixtures of α- and β-lactose. Isosweet sucrose concentrations for three different concentrations of β- and equilibrium lactose and two concentrations of α-lactose are reported.     

EXTENDED VALIDATION OF A SIMPLIFIED EXTRACTION AND GRAVIMETRIC DETERMINATION OF TOTAL FAT TO SELECTED FOODS

A simplified method for chloroform/methanol extraction and gravimetric determination of total fat previously published for diet composites was tested on additional foods, including milk, cheese, fried snack foods, nuts/seeds, salad dressings, baked goods, meat, fish/shellfish and fruits/vegetables. Homogenized food composites and certified reference materials (CRMs) were analyzed using the existing method involving, briefly, orbital shaking of a subsample with chloroform/methanol/buffer in specific proportions, then recovery of total lipid in the chloroform extract. For meat, fish, shrimp, cheese and fried plantains, total fat recovery was low and/or variability was high with the unmodified assay versus results from other standard total fat methods (e.g., ether extraction, acid hydrolysis) or to CRM assigned values. Reducing the sample size or adding a homogenization step during extraction resulted in relative standard deviations of < 3% for all matrices and also values consistent with those generated by other standard total fat methods and within assigned ranges for total fat in most CRMs.

PRACTICAL APPLICATIONS

The method allows for routine batch analysis of multiple samples of a range of food types with minimized hands-on time, using commonly available laboratory equipment. The resulting total lipid extract can be subdivided for analysis of various specific lipid analytes as well as for gravimetric measurement of total fat.     

Effect of nisin on the shelf-life of pasteurized double cream

Nisin was found to extend the shelf-life of pasteurized double cream if post-pasteurization contamination was eliminated. Nisin had little effect on the organoleptic properties of cream but enhanced proteolysis by Gram-negative organisms. A negative correlation was observed between nisin degradation in the cream and extension of the shelf-life. There was also a correlation between nisin degradation and the extent of proteolysis in the creams.     

EFFECTS of FEED MOISTURE and BARREL TEMPERATURE ON the RHEOLOGICAL PROPERTIES of EXTRUDED COWPEA MEAL1

Decorticated cowpea meal was adjusted to 20, 30, and 40% moisture and extruded in a Wayne pilot-scale extruder at barrel temperatures of 150, 175 and 200°C. the resulting products were subjected to rheological evaluation using the Instron Universal Testing Machine equipped with standard tensile jaws, the Warner-Bratzler shear device and the Kramer Shear Press. Regression equations relating rheological properties to feed moisture and barrel temperature were computed from the data, and response surfaces were generated from these models. Tensile strength of extrudates was greatest for the dense products produced in the low moisture-low temperature region and declined at higher moistures and temperatures. Shear strength as determined by either the Warner-Bratzler or Kramer devices exhibited a ridge of high values extending from 20%-150°C to 30%-200°C, and declined for brittle, expanded products made at low moisture and high temperature and for soft products made at high moisture.     

Study of Acetylated Food Proteins by Raman Spectroscopy

ABSTRACT: Three food proteins, soy protein isolates, spray-dried egg white, and whey protein isolates, were acetylated to varying levels, and the extent of modification was determined by wet chemistry methods. Raman spectra of the modified proteins were obtained. A new C=O stretching vibration was observed at 1737cm-1 and was attributed to ester carbonyl groups appended to the proteins during acetylation. Calibration curves were obtained by plotting the intensity ratio of this Raman band to the 1003cm-1 phenylalanine stretching band against the extent of substituted hydroxyl groups. Linear fits were obtained with correlation coefficient r > 0.9979. The Raman spectral data were also analyzed to study the effect of acetylation on the conformation of the 3 proteins. Marked conformational changes were observed in the modified proteins.     

Intermediate-band solar cells based on dilute alloys and quantum dots

This paper describes our recent developments of intermediate-band solar cells, with a focus on the use of dilute alloys and nanostructured materials such as quantum dots (QDs). The concept of"full-spectrum" solar cells and their working mechanism with various material structures based intermediate-band solar cells, including material growth, structural and chemical analysis, device modeling and testing, are presented. Finally, the progress and challenges of quantum-dot-based solar cells are discussed.     

A Superplastic Al-Li-Cu-Mg-Zr Powder Alloy with High Hardness and Modulus

Structure/property studies were made on an experimental Al-3.18% Li-4.29% Cu-1.17% Mg-0.18% Zr powder alloy, which is of the low density/high modulus type. Alloy powder was made by the P&W/GPD rapid solidification rate (RSR) process, canned, and extruded to bar. The density was 2.458 × 10⁶ g/m³. The material was solution-treated, and aged at 149°C (300°F), 171°C (340°F), and 193°C (380°F), using hardness tests to determine the aging curves. Testpieces solution-treated at 516°C (961°F) showed an average yield strength (0.2% offset) of 43.3 ksi (299 MPa) and ultimate tensile strength of 50.0 ksi (345 MPa), with 1% elongation, which increased to 73.0 ksi (503 MPa) and 73.1 ksi (504 MPa), respectively, with only 0.2% elongation, on peak aging at 193°C (380°F), with a modulus of elasticity of 11.4 × 10⁶ psi (78.3 GPa). Hardness values reached 90–92 R_B on aging at 149–193°C (300–380°F). The as-extruded alloy showed superplastic behavior at 400–500°C (752–932°F) with elongations of 80–185% on 25.6 mm, peaking at 450°C (842°F). An RSR Al-2.53% Li-2.82% Mn-0.02% Zr extruded alloy showed only 18–23% elongation at 400–500°C (752–932°F).