TEXTURE OF CULTURED GILTHEAD SEA BREAM (SPARUS AURATA): INSTRUMENTAL AND SENSORY MEASUREMENT

The texture of twelve samples of farmed gilthead sea bream (Sparus aurata) from experimental and commercial cultures, fresh and frozen, was determined by instrumental texture profile analysis (TPA) of whole raw fish and by sensory analysis of the corresponding cooked fish fillets. Average values of TPA hardness and chewiness were higher for fresh samples (78.0 N and 41.9 N, respectively) than for frozen and thawed samples (43.5 N and 21.5 N, respectively). The effect of freezing on springiness and cohesiveness values was different depending on the sample (a significant sample × freezing interaction). By sensory analysis, higher firmness, chewiness and fibrousness, and less juiciness were detected in frozen samples. Only one sample was perceived as less chewy, less fibrous and more juicy than the rest, and that corresponded to the smallest (less mature) fish. High percentages of the variability of sensory firmness (92%), chewiness (91%) or juiciness (85%) were explained by several of the TPA parameters measured on the raw whole fish using a fast nondestructive test.     

LOW TEMPERATURE BLANCHING OF FROZEN CARROTS WITH CALCIUM CHLORIDE SOLUTIONS AT DIFFERENT HOLDING TIMES ON TEXTURE OF FROZEN CARROTS

The objective of this study was to evaluate the effect of low temperature blanching in calcium chloride solutions to increase firmness retention of frozen carrot slices and to determine optimum conditions to provide a final product with maximum firmness. Low temperature (65 C) blanching in CaCl² solutions (0.05–0.6 molar) for holding times (5–90 min) was performed on carrots 'Apache' cultivar. Calcium absorption was affected (P≤0.05) by the CaCl² concentration. Behavior of this variable was adequately fitted by a second order model (R²=0.99). Firmness was affected (P≤0.05) by the CaCl² solutions and holding times. Optimum conditions gave extrusion forces of 1693–2095 N and calcium levels of 69–144 mg/100 g. These were verified experimentally and agreed closely with predicted calcium absorption and firmness values.     

TENDERNESS ANALYSIS AND CONSUMER SENSORY EVALUATION OF OSTRICH MEAT FROM DIFFERENT MUSCLES AND DIFFERENT AGING TIMES1

Six ostrich carcasses were split and aged for 1 h, 1 day, or 1 week, roasted to 75 C and evaluated for tenderness and sensory attributes. Shear values for aged ostrich meat were 10.1, 10.0, 10.0, and 14.1 kg/g for 1 h, 1 day, 1 week, and the beef control, respectively. The most tender ostrich muscles identified were: M. iliofibularis, M. iliofemoralis, and M. oburatorius lateralis. Tenderness was affected by fiber orientation of the meat after slicing. Shear values were higher (p<0.05) for the longitudinal fiber orientation (11.5 kg/g) compared with the transverse fiber orientation (7.4 kg/g). A 9–point hedonic scale and a consumer sensory panel were used to evaluate tenderness, flavor, and overall acceptance of selected cuts. Ostrich meat aged for 1 week provided higher (p<0.05) liking scores for flavor compared with lesser aged ostrich or the beef control. This study suggests that prepared ostrich meat provides a good alternative compared with a similar beef product.     

BIOCHEMICAL PROPERTIES OF ACTOMYOSIN AND EXPRESSIBLE MOISTURE OF FROZEN STORED ADDUCTOR MUSCLES OF PATAGONIAN SCALLOP (ZYGOCHLAMYS PATAGONICA)

The biochemical properties of actomyosin and the expressible moisture of frozen stored adductor muscles of scallop (Zygochlamys patagonica) were investigated. After freezing (zero time of storage) both the enzymatic activity and the reduced viscosity of actomyosin remained unchanged with respect to those corresponding to actomyosin from unfrozen muscles. Both parameters significantly decreased (P < 0.01) at 4 months of frozen storage and thereafter gradually decreased. No significant differences (P > 0.01) were observed in the relative percentages of myosin, actin, and in the myosin/actin ratio up to 4 months of storage. Thereafter myosin significantly decreased (P < 0.01) up to the end of storage. The decrease in the biochemical properties of actomyosin was accompanied by a loss in the water holding capacity of the muscles.     

冻藏时间对速冻水饺品质影响的试验研究

主要考查冷冻保藏时间对于速冻水饺的理化性质、微生物指标及感官性状的影响。结果表明,随保藏时间延长,饺皮的水分含量呈线性规律下降,从最初的（37．25&#177;0．44）％降至试验末期的（32．5&#177;0．92）％。而对于样品的酸价,随保藏时间延长,酸价升高,从初始的（2．01&#177;0．01）mg KOH／g升至试验末期的（2．38&#177;0．02）mgKOH／g。菌落总数及嗜冷菌菌落总数结果相似,都随保藏时间延长而增加,菌落总数从（1．27&#177;0．09）&#215;10^5 cfu／g升至（3．26&#177;0．08）&#215;10^5 cfu／g,而嗜冷菌菌落总数从（2．44&#177;0．06）&#215;10^5 cfu／g升至（3．73&#177;0．15）&#215;10^5 cfu／g。结合对水饺饺皮和饺馅的感官评价表明,速冻水饺的食用品质随保藏时间呈下降趋势,相对来讲,保藏时间越短,样品的食用品质越好。     

EFFECTS OF MODIFIED ATMOSPHERE PACKAGING AND FILM ON SENSORY AND STORAGE PROPERTIES OF FROZEN HAM STRIPS

The effectiveness of modified atmosphere packaging and barrier properties of films upon the product attributes of frozen (IQF) ham strips, that are normally found at salad bars, was studied every 28 days over a period of 196 days. Three gases/mixture were used (CO₂, N₂ and ambient air) for flushing two pouches, one made from normal barrier film (861) and the other from a high barrier film (863). A triangle test and sensory evaluations were performed by a semi-trained panel (six members) for the following traits: freshness, structure, mouth feel, overall evaluation, aroma, appearance and off-flavors. Overall evaluation scores were acceptable up to 140 days of storage, regardless of the pouch used, but from 140 to 196 days, the product would be only marginally acceptable. Ham strips stored in N₂ or CO₂ atmospheres had a higher acceptance level than those stored frozen in ambient air. Panelists distinquished between fresh and stored product more frequently (75%) when the product was stored in ambient air pouches rather than CO₂ or N₂ atmospheres. Pouches made from the higher barrier film had lower (398/g) total aerobic plate counts than pouches (736/g) made from normal barrier film, but these counts are low and would be acceptable in industry.     

SOFTENING AND BIOCHEMICAL CHANGES OF SAPOTE MAMEY FRUIT (POUTERIA SAPOTA) AT DIFFERENT DEVELOPMENT AND RIPENING STAGES

We investigated some of the physicochemical and biochemical factors associated with flesh softening of sapote mamey fruit during development and ripening. The activities of pectinmethylesterase (PME), polygalacturonase (PG) and β‐galactosidase (β‐GAL) enzymes were measured in fruits harvested at different development stages, and postharvest in two production seasons. The textural changes were most noticeable at the preclimacteric stage in ripening fruit. The water‐soluble pectin (WSP) increased at a different rate than firmness decreased. No correlation between PG or PME activity and changes in firmness was observed in ripening fruits, though a low correlation was seen between β‐GAL activity and softening in climacteric stage. Greatest loss of firmness occurred in climacteric stage. Fruit pulp softening was not dependent on a single enzyme activity.     

BIOCHEMICAL AND ANTIBACTERIAL PROPERTIES OF LYSOZYME PURIFIED FROM THE VISCERA OF SCALLOPS (PATINOPECTEN YESSOENSIS)

A lysozyme was purified from the viscera of scallops by ion exchange, gel permeation and affinity chromatographies. The yield of the purified lysozyme was 1.52%, and its purification ratio was 411.9 folds. The molecular weight of the scallop lysozyme was about 14.5 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimal temperature for lysozyme activity was 20C, but the optimal stability temperature was between 20 and 30C.
The optimal pH for lysozyme activity was 5.0, but the optimal stability pH was between 5.0 and 6.0. Scallop lysozyme had antibacterial activities against both gram-positive and gram-negative bacteria in which gram-negative bacteria, Escherichia coli and Vibrio vulnificus, were inhibited more effectively than gram-positive bacteria. Egg white lysozyme inhibited gram-positive bacteria better than the scallop lysozyme, whereas the reverse was true for gram-negative bacteria. The N-terminal sequence of the scallop lysozyme consisted of 10 amino acids: proline, cysteine, valine, tyrosine, alanine, phenylalanine, methionine, asparagine, glutamic acid and aspartic acid.

PRACTICAL APPLICATIONS

Egg white lysozyme (EWL) has been used as a preservative or antibacterial agent in the pharmaceutical and food industry, but is limited to broaden its application because of poor antibacterial activity against gram-negative bacteria. Scallop viscera lysozyme has two times higher antibacterial activity against gram-negative bacteria ( Escherichia coli and Vibrio vulnificus ) than EWL. Therefore, scallop viscera lysozyme shows a promise as a bacteriostatic or prophylactic agent in food preservation and specialty product.     

RHEOLOGICAL, MELTING AND MICROSTRUCTURAL PROPERTIES OF CHEDDAR AND MOZZARELLA CHEESES AFFECTED BY DIFFERENT FREEZING METHODS

Three cheeses were treated by (1) blast, (2) precooling plus blast, (3) liquid nitrogen and (4) precooling plus liquid nitrogen freezing methods. Mozzarella I and Cheddar cheeses treated by all methods had lower shear strength than their controls, excepting Mozzarella I treated by (1) was similar to its control. Mozzarella II treated by (1) and (2) had higher shear strength than its control but by (3) and (4) it had less. The failure stresses of Cheddar and Mozzarella I cheeses treated by (1) and (2) were significantly lower than their controls, while treated Mozzarella II had opposite results. Mozzarella I treated by (2) had meltability similar to its control and by (1) had lower meltability. Mozzarella II meltability was significantly reduced by (1) and (2). Stretchability was greatly improved using both methods for Mozzarella I but not for Mozzarella II. Cryo‐stage Scanning Electron Microscopy (SEM) showed that the microstructural differences caused by (1) and (2) were apparent in Cheddar and Mozzarella II but not in Mozzarella I.