Relative Protein Efficiency Ratios for Wheat-Based Breakfast Cereals

Male weanling rats were subjected to standard 28-day PER trials following the outline by the AOAC (1984) except that the diets contained 8.5% protein (N × 6.25) as one of six wheat-based breakfast cereals, white flour, whole wheat flour or casein. One of the cereals was an extrusion puffed product, three were flaked and toasted cereals and two were extruded cereals. Of the two extruded cereals, one was lightly toasted and the other was more heavily toasted. Relative PER (R-PER) was lowest for the puffed cereal (- 15.3) and highest for the extruded-lightly toasted cereal (69.9). R-PER for the flaked cereals ranged from 1.7 to 16.3; the other extruded cereal had a R-PER of 2.8 and each of the two flours had a R-PER of 42.9.     

Influence of Tertiary Butylhydroquinone and Certain Other Surface Coatings on the Formation of Carbonyl Compounds in Granulated Roasted Peanuts

A 15-month shelf life study was conducted with granulated roasted peanuts (Arachis hypogaeu L.). The nuts were coated with combinations of 0.01, 0.02, and 0.03% tertiary butylhydroquinone (TBHQ) antioxidant, two fats and an acetylated monoglyceride. Total carbonyls were measured monthly and served as an index of oxidative rancidity. TBHQ combined with citric acid was an effective anitoxidant in inhibiting carbonyl production, while the fats and monoglyceride coatings alone had no significant effect on carbonyl production. Samples without TBHQ exhibited a fivefold increase in total carbonyl content compared with samples treated with TBHQ. Total carbonyl levels of granulated peanuts treated with 0.02% TBHQ, the level presently allowed by the FDA, increased 20% during the 15-month storage period compared with an increase of 110% for those without TBHQ.     

INJURY AND SURVIVAL OF AEROMONAS HYDROPHILA 7965 AND YERSINIA ENTEROCOLITICA 9610 FROM HIGH HYDROSTATIC PRESSURE

Responses of Aeromonas hydrophila 7965 and Yersinia enterocolitica 9610 to high hydrostatic pressure were investigated in microbiological media and meat. Cultures were pressurized from 51 to 304 megaPascals (MPa) for 15 min in 200 mM sodium phosphate buffer (pH 7.0), tryptic soy broth and radiation-sterilized ground pork. Trends in pressure response were similar in all three pressure menstrua. A 7-log₁₀ CFU/g reduction of A. hydrophila in pork resulted from treatment of 253 MPa for 15 min. A 7-log₁₀ CFU/g reduction of Y. enterocolitica in pork resulted from treatment of 304 MPa for 15 min. Pressure-induced injury of both pathogens was detected in all pressure menstrua at most pressure levels. No growth of either pathogen occurred in irradiated pork after pressurization of 128–203 MPa for 15 min and storage at 4C for 14 days; however, an upshift to 30C of cold-stored A. hydrophila in pork resulted in growth after a lag time of approximately 10 h, and an upshift to 30C of cold-stored Y. enterocolitica in pork resulted in recovery of injured cells within 2 h, and growth after a lag time of 4–6 h. This suggests that temperature abuse (30C) of pressure-processed pork for greater than 6 h would allow growth and possibly repair of A. hydrophila and Y. enterocolitica which survive following pressure treatment. Although neither the processor nor the consumer would likely abuse the product to such an extent, the results suggest that A. hydrophila and Y. enterocolitica have the ability to repair or grow following pressure treatment in pork.     

EFFECT OF SUGARS ON THE THERMAL AND RETROGRADATION PROPERTIES OF OAT STARCHES

The thermal and retrogradation properties of oat starches from two cultivars (NO 753-2 and AC Stewart) were characterized in the presence of glucose, fructose and sucrose at a concentration of 36% w/v. In both oat starches, amylose leaching (AML) and swelling factor (SF) decreased in the presence of sugars (sucrose > glucose > fructose). These decreases were more pronounced in AC Stewart starch. The decrease in AML showed that sugars interact with amylose chains within the amorphous regions of the starch granule. The gelatinization transition temperature and the enthalpy of gelatinization increased in the presence of sugars (sucrose > glucose > fructose). The above increase was also more pronounced in AC Stewart starch. The decrease in SF and the increase in gelatinization parameters indicated that these changes were influenced by the interplay of factors such as starch-sugar interaction, changes in water structure in the presence of sugars, and the antiplastizing properties of sugars relative to water. The retrogradation enthalpy and the X-ray diffraction intensities of NO 753-2 and AC Stewart starch gels (stored at 4C) increased in the presence of sugars (glucose > fructose > sucrose). These changes were more pronounced in NO 753-2 starch. The results showed that interaction (during storage) between leached amylopectin and sugar molecules was the main causative factor influencing oat starch retrogradation.