Comparative gamma radiation sensitivity of Tribolium madens (Charpentier) and T. castaneum (Herbst)

The effects of gamma radiation doses between 5 and 100 krad on all metamorphic stages of Tribolium madens and T. castaneum were studied. Results from the two species were similar although T. madens appeared to be more radiosensitive. The development of adults from treated eggs and larvae was prevented by 5 krad in T. madens and by 10 krad in T. castaneum. Some adults emerged from treated pupae at all treatment levels, but no reproduction occurred at 20 krad or above. Adult females of both species were more sensitive to the sterilizing effects of gamma radiation than were males, but sterility of both sexes was effected at doses of 30 krad and above. Control of these two species appears feasible with levels of radiation currently approved for treatment of stored-grain insects in wheat and wheat flour.     

PATTY FORMATION METHOD, THICKNESS AND WEIGHT EFFECTS ON PROPERTIES OF COOKED LOW-FAT BEEF PATTIES

Effects of patty thickness (0.95 and 1.27 cm), weight (90 and 113 g) and type of patty fill method (traditional gravity fill = FF and twisted through holes into mold = TF) were evaluated using low-fat (10%) ground beef. An increase in patty thickness from 0.95 cm to 1.27 cm, resulted in a decreased (P<0.01) sensory firmness and peak load (Newtons) and increased (P<0.01) initial juiciness. TF fill method and 1.27 cm thick FF treatments improved tenderness and juiciness over 0.95 cm thick FF patties. This study revealed that improvements in tenderness and juiciness of low-fat beef patties can be attained through use of appropriate patty formation procedures.     

Effect of fatty acid positional distribution and triacylglycerol composition on lipid by-products formation during heat treatment: I. Polymer formation

Effects of the fatty acid positional distribution and of the triacylglycerol (TG) composition on polymerization of TG during heat treatment were studied. Diacid TG molecules, acylated only with linoleic acid or linolenic acid along with palmitic acid, and positioned either in the central position (PLP and PLnP, respectively) or in one of the two outer positions (PPL and PPLn, respectively) were synthesized. Monoacid TG, i.e., trilinolein and trilinolenin, were also synthesized and mixed with tripalmitin in a 1:2 ratio. These model TG were also compared to TG models that consisted of a canola oil and its randomized counterpart, whose fatty acid positional distribution and TG composition were determined by means of high-performance liquid chromatography (HPLC). After heating, the polymer content and composition were evaluated by HPLC-size exclusion chromatography. Both pure TG and the canola oil models showed that acylation of polyunsaturated acids in the central position was protective against polymerization, although the effect was mainly observed with linolenic acid. The synthetic-TG study showed that the monoacid TG species exhibited higher sensitivity toward polymerization than the diacid species. The slight differences in the TG species between both canola oils did not allow observation of such a relationship with regard to TG composition.     

Ice Adhesion to Hydrophilic and Hydrophobic Surfaces

The adhesional shear strength has been determined for ice formed against polished steel, monolayers adsorbed on steel and thin plastic coatings painted on metal surfaces. The adsorbed monolayers reduced the shear strength to about one-third of that for ice on clean steel. The monolayers also had the effect of changing the character of the breaks from clearly cohesional to apparently adhesional failure. The shear strength from the plastic coatings ranged from values equal to that of ice against clean steel to values 70 to 80% lower. The reduction in shear strength did not correlate with the water contact angle on the coatings but was usually found to be due either to air entrapment at the ice/coating interface or to cohesive failure of the coating itself.

The ice separated from the various substrates was examined microscopically by forming plastic replicas of the ice surface. These studies helped determine the mechanism of failure and, since one of the replicating solutions was also an ice etchant, much was learned about the crystal structure and the crystal defects of ice near surfaces. The ice lattice was found to be highly defective near the substrates and this is discussed in connection with the “liquid-like,” behavior of interfacial ice.     

Use of dielectric spectroscopy to assess adhesively bonded composite structures,Part III: Investigation of mechanical strength

This paper explores the way in which the data obtained from the dielectric study (reported in Part II of this 3-part series of articles), can be related to the mechanical strength of the bonded structure. Exposure of the adhesive bonded joints to a hot and wet environment leads to a loss of strength. Changes are observed in the dielectric properties on exposure to the humid environment, and an attempt is made to relate these observations to the mechanisms leading to loss in the mechanical strength ofthe bond. The observation of a correlation between the changes in these physical properties indicates the possibility ofusingdielectricspectroscopyas a powerful nondestructive evaluation (NDE) technique for bonded composite structures.     

Adhesion of Small Spherical Particles to Substrates Immersed in Liquids

The force required to start small, untreated or siliconized glass spheres rolling on an inclined copper-coated glass surface was determined in water and biphenyl melt. The results establish there are van der Waals attractions between the spheres and substrate. Hamaker coefficients of the studied systems were calculated.