A Gas-Probe Analysis of Structure in Silicate Glasses

An analysis of helium and neon transport in vitreous silica is consistent with a statistically distributed structure of the random network. The jump distance, d , for diffusion in common borosilicate glass is greater than in vitreous silica due to the additional modifier ions, Na⁺. The addition of Na⁺ or K⁺ to a silicate structure produces an increase in d . The vibrational frequencies for a gas atom in a "doorway" ( v *) and in a solubility site ( v ) indicate structural trends such as phase separation.     

Moisture Loss in Tray-Packed Fresh Fish During Eight Days Storage at 2°C

Effects of moisture loss in tray-packed fresh fillets of Flounder (Pogonias cromis), Red Snapper (Litjanus blackfordii), Croaker (Micropogon undulatus) and Ocean Perch (Sebastes marinus) were studied. The fish, purchased from seafood suppliers and processed into fillets at their prospective plants, were packaged in plastic foam trays lined with absorbent pads, overwrapped, and subsequently stored at 2°C (35.6°F) for 8 days. Gross and net weights decreased whereas the percent drip increased for all fish during storage. Except for croaker, the total moisture content remained virtually unchanged for all fillets during storage. The acceptability of all fillets decreased as the Trimethylamine-Nitrogen concentrations increased.     

High Vacuum Flame Sterilization of Canned Diced Tuna: Preliminary Process Development and Quality Evaluation

A preliminary study of the potential of high vacuum flame sterilizing canned diced tuna was carried out. The investigation included inoculated experimental sighting packs study at five process levels, and comparative assessment of the physical, chemical and nutritional property of the raw, precooked, high vacuum flame sterilized (HVFS) and still-retorted canned tuna. The vacuum achieved in the HVFS packs was significantly higher (P < 0.05) than the control packs. Fatty acid and amino acid composition, in-vitro protein digestibility, and the Computed Protein Efficiency Ratio (C-PER) were similar for the raw, precooked and canned tuna. Available lysine was marginally decreased by precooking, and HVFS processing caused no measurable change. However, available lysine, thiamin, riboflavin, niacin and mineral concentrations were generally lower in the retort process control canned tuna.     

Modified Atmosphere Storage of Dungeness Crab (Cancer magister)

A modified atmosphere (MA) of 80% CO₂ and 20% air coupled with refrigerated storage was effective in extending shelf life of cooked whole Dungeness crab. Aerobic plate counts were lower over the storage period tested (25 days) for samples held in MA compared to controls held in air. Tissue pH decreased in MA samples, but increased in samples held as air controls (AC). There were significant differences in redox potential between groups, but these did not appear large enough to affect bacterial growth. Trimethylamine and ammonia values were similar for 14 days, then became higher in controls. There were no differences between treatment groups in thiobarbituric acid values, in textural properties as determined by Instron or in reflectance measurements. After removal from MA storage, the crab had a microbial shelf life that mimicked that of a fresh product.     

EFFECTS OF END-POINT TEMPERATURE AND FAT LEVEL ON THE RESIDUAL CHOLESTEROL IN GROUND BEEF PATTIES1

Patties of lean ground beef with 2% fat (L2PF) and 6% fat (L6PF) were used to study the fat and cholesterol composition of raw and cooked ground beef and to determine how the end-point cooking temperature affects the amount of fat and cholesterol in a lean ground beef patty as it would be eaten by the consumer. The two patty types were obtained from the longissimus muscle of steers with marbling scores associated with “Standard” to “Select” and “Select” to “Choice” U.S. carcass grades of beef, respectively. All steers were fed a diet of roughage and concentrates to ensure fat deposition over the 12th and 13th ribs; longissimus muscles between the 7th and 10th ribs were removed, trimmed of all external fat, ground and formed into three 130-g patties. One patty was fried to an internal temperature of 60C, another to 71C and the third was uncooked. After frying, the patties were measured for drip loss, moisture and total fat. The fat extract was used for cholesterol analysis. The cooked L2PF sample had significantly less fat than the cooked L6PF samples, but there was no difference between the L2PF and L6PF in cholesterol. End-point temperature had no effect on the fat and cholesterol contents for either L2PF or L6PF samples, but the higher end-point temperature resulted in a significant loss of moisture.