UTILIZATION OF MINCED SUCKER FLESH

Freshwater suckers (Catostamidae family) were obtained from Lake Huron to study the possibility of developing new products utilizing its flesh and the influences of additives on the functionality of sucker muscle proteins. Results showed that sodium chloride increased protein solubility, but also decreased swelling, gel forming and pH. In comparison, sodium tripolyphosphate increased protein solubility, pH, swelling and gel formation. Fish sausages and canned products showed low binding characteristics. However, adding corn meal and soy protein in combination with sodium chloride and sodium tripolyphosphate improved their water holding capacity, texture and cook yield. It was concluded that sodium tripolyphosphate, corn meal and fat should be used in manufacturing minced sucker products.     

TEXTURAL CHANGES IN RIPENING PLANTAINS*

Compression testing indicated that the ripening of plantains is accompanied by textural changes which include a considerable decrease in the apparent compressive strength and the overall textural uniformity. The magnitude of the apparent strength was found to depend on the specimen's diameter. The prefailure deformation increased during ripening and reached a maximum level of 40-45%. After this stage, the prefailure deformation declined as the fruit's flesh continued to soften. Unripe fruits could be distinguished from ripe fruits not only by the magnitude of these parameters but also by the failure pattern. The failure of unripe fruits was characterized by an instant formation of a single inclined failure plane, and that of ripe fruits by a progressive development of multiple irregular planes. The shift in the failure pattern may serve as a textural criterion for fruit ripeness.     

QUANTITATIVE CHANGES IN WHOLE MYOFIBRILS AND MYOFIBRILLAR PROTEINS DURING FROZEN STORAGE OF TRUE COD

The extractability of whole myofibrils from true cod decreased more rapidly during frozen storage at −40°C than did the extractability of the component myofibrillar proteins. There was a 95% decrease in extractable myofibrils after 6 months in storage, but only a 23% decrease in extractable myofibrillar proteins.     

CONTRACTIBILITY OF MUSCLE FIBRES AS A POSSIBLE AID TO JUDGING TEXTURAL CHANGES IN FROZEN MEATS AND FISH

Abstract Following addition of ATP, the contractibility of muscle fibres in suspension (obtained by muscle homogenization) changes during frozen storage of the muscle. These changes were detected by turbidity measurements. In beef, there were no significant changes up to 6 months storage at— 8°C or lower. Considerable loss in contractibility occurred in chicken white muscle. Losses were rapid in cod and carp muscle, contractibility being completely lost in one month at— 3°C. The method is proposed as one criterion for judging textural changes in lean fish during frozen storage.     

EFFECT OF VACUUM PACKAGING ON CHANGES ASSOCIATED WITH FROZEN COD FILLETS

Protein solubility of cod fillets sealed under vacuum was significantly higher at all sampling times than from fillets sealed in presence of air during an 18 months storage study at −25°C. Frozen storage resulted in substantial loss of protein from all of the bands of the PAGE pattern, with more pronounced loss from the myosin heavy chain, actin and tropomyosin bands. Dimethylamine and malonaldehyde concentrations were not significantly different between the air and vacuum pack. Significant losses in flavor and textural quality during frozen storage were detected. Crosslinking, responsible for the observed reduction in protein solubility of raw tissue, appears to be of relatively weak nature, since little toughening was detected in the cooked tissue.     

TEXTURAL AND STRUCTURAL CHANGES IN LASAGNA AFTER COOKING

The effects of cooking time (9.5, 11, and 15 min) and holding time of lasagna pasta after cooking (4 min to 185 min) on the textural properties (through mechanical testing) and internal structure (via nuclear magnetic resonance imaging) were studied. The peak force, which characterized firmness, decreased with increasing cooking and holding time. Work was strongly influenced by the value of the peak force and followed a similar trend. Corresponding NMR images revealed changes in proton signal intensity as a function of position. The NMR signal intensity increased at the center with increasing cooking and holding times. This change illustrates that water migration to the sample center was simultaneous with the decrease in the peak force. The initial slope, associated with the structure of the sample surface region, decreased with cooking time and increased with holding time. The NMR signal intensity of the surface region decreased with holding time; water migration from this region during this period was simultaneous with an increase in stiffness. NMR imaging is an effective technique to evaluate internal structural changes of pasta during holding. Furthermore, it supplements information provided by conventional mechanical testing, facilitating the interpretation of texture measurements.     

QUANTITATIVE STUDIES OF PROTEOLYTIC AND LIPOLYTIC BACTERIA IN FROZEN MINCED BEEF AND HAMBURGER

Sixty frozen samples (30 hamburger patties and 30 minced meat) purchased from different retail markets in Ismailia, Egypt were examined for incidence of proteolytic and lipolytic bacteria. Mean values of proteolytic psychrophiles in the examined samples of hamburger and minced meat were 2×10⁵ and 6×10⁴, respectively. Lipolytic psychrophiles in hamburger were 8×10⁵ and 3×10⁵ in minced meat. Proteolytic mesophiles in hamburger and minced meat were 6×10⁵ and 5×10⁴, respectively. Mean values of lipolytic mesophiles were 5×10⁴ for hamburger and 5×10³ for minced meat. Proteolytic thermophiles in hamburger and minced meat were 3×10³ and 10³, respectively. Both proteolytic and lipolytic activities were exhibited by various bacteria that were identified.     

ULTRASTRUCTURAL AND TEXTURAL CHANGES IN PROCESSED CARROT TISSUE1

Processed carrot tissues were studied using a transmission electron microscope (TEM) and an Instron Universal Testing Instrument. Carrot slices were evaluated raw, after thermal processing and after freezing and thawing. Cell walls of carrot tissues, frozen and thawed, were intact and dense. The middle lamella lost pectic materials. Overall, frozen and thawed cells were not so closely pressed as those of raw tissues. In thermally processed carrots the cell wall and the middle lamella were less densely stained compared to raw or frozen-thawed carrots. Thermally processed carrots exhibited significantly smaller modulus of deformability and stiffness and toughness values than raw carrots. There were no significant differences between the modulus of deformability and stiffness values for frozen-thawed and thermally processed carrots. Toughness values were, however, significantly lower for the thermally processed in comparison with the frozen-thawed carrots. Instrumental texture measurements indicated that different areas of carrot tissue behave differently to thermal processing.     

FROZEN STORAGE QUALITY CHANGES IN WHOLE JONAH CRABS

The Jonah crab is an underutilized species in the mid-Atlantic region, and use of the whole, frozen crab would broaden marketing options for this seafood product. We monitored quality changes in whole cooked crabs held in a blast freezer for up to 50 weeks. A sensory evaluation panel determined the point at which detectable differences appeared in the product. Microbiological testing was conducted at selected intervals to assess bacterial content. In a triangle test, frozen experimental samples of leg meat were first differentiated from frozen controls at approximately 24 weeks. No significant difference was defected in body meat for up to 33 weeks’ storage. Microbial quality was acceptable throughout the experiment.