Longissimus dorsi (loin) and gluteus medius (rump) muscles were obtained from twenty carcasses (ten grain-fed and ten forage-fed). A trained sensory panel rated longissimus dorsi steaks from grain-fed animals significantly (p < 0.05) more tender and more flavorsome than those from forage-fed animals. Fatty acid profiles indicated some significant differences due to feeding regimen. Forage-fed beef had a higher proportion of omega-3 polyunsaturated fatty acids than grainfed beef.

No abstract

The physicochemical properties of eight extracellular proteinases secreted by psychrotrophic bacteria of dairy origin have been studied. Seven of these proteinases were able to withstand ultra heat treatment (UHT) with D values at 140 °C ranging from 2 to 300 s. The six Pseudomonas fluorescens proteinases were glycoproteins of mol. wt 47000-49500. The two Serratia marcescens proteinases, of mol. wt of 51000, did not contain carbohydrate but in other respects were similar to the Pseudomonas proteinases. The proteinases were inhibited by various metal chelators and all contained Ca and Zn in similar proportions. Their amino acid compositions were similar, with alanine as the N-terminal group, cysteine completely absent and very low levels of methionine. Isoelectric points ranged from 5-10 to 8-25. Their physical and chemical properties enabled them to be classified as alkaline metalloendopeptidases. A similarity index (SAn) was used to predict sequence homology between ten proteinases of known amino acid composition. Comparisons of SAn of these proteinases showed only minor sequence differences except for those of Ps. fluorescens MC60. Heat resistance could not be related wholly to similarities in protein sequence, but could be related both to the strength of stabilizing Ca 2+ -protein interactions and to the randomness inherent within the folding of the peptide chain.

The effects of electrical stimulation, tender stretching, ageing, freezing and thawing on beef palatability were assessed by a trained sensory panel and by several objective methods. The overall palatability of both longissimus dorsi (strip loin) and semimembranosus (topside) steaks improved with ageing, irrespective of tenderizing method, but there appeared to be little advantage in extending ageing beyond 10 days. Tender stretched longissimus dorsi steaks were marginally preferred by the taste panel to electrically stimulated steaks subjected to the same ageing. Unfrozen steaks were preferable to frozen and thawed steaks with respect to juiciness, flavor and tenderness. Thawing method had little effect on steak palatability.

Irradiation treatmentSweetlip (Lethrinus miniutu.s), red emperor (LZ@IU.S sebae), mackerel (Scomberomorus commerson), whiting (Sillago ciliutu), mullet (Mu@ cephulus), barramundi (Lutes culcurzfer), sand crab (Portunus pelugicus), Moreton Bay prawns (Metupenueus spp. ) and king prawns (Penueusplubujus) were irradiated at doses of 0, 1, 3 and 5 kGy. A dose of 1 kGy resulted in a 1.5 to 4 log reduction in total bacterial numbers. Sensory quality decreased with increasing radiation dose except for Moreton Bay prawns and cooked king prawns, which were acceptable after a 5 kGy dose. Doses higher than 3 kGy caused adverse odor and flavor changes in Moreton Bay and cooked king prawns. A dose of 1 kGy could extend storage life of any of the species without adversely affecting sensory quality.Seafood packs were stored in crushed ice within insulated containers and irradiated in a small batch plant with a %o plaque source (Izard, 1985) within 24 hr of purchase. The source had an activity of 69,000 curies. Seafood was given a 0, 1, 3 or 5 kGy irradiation dose at a dose rate of 7.2 Gy/min as determined by ceric-cerous sulphate dosimetry. These doses were minimum in all cases (minimum to maximum ratios < 1:1.3). Temperature of the seafoods remained at 2°C throughout irradiation. Following irradiation, one pack of each seafood from each treatment was randomly selected and held chilled. All other packs were immediately blast frozen (-40°C) for subsequent sensory evaluation. All evaluations were completed within 3 wk of irradiation.