Effect of frozen storage on the biochemical, microbial and sensory attributes of Skipjack Tuna (Katsuwonus pelamis) fish loins

Skipjack tuna (Katsuwonus pelamis) belongs to the Scombridae family to determine the consistencycharacteristics of tuna fish loins for 28th days at frozen (−18 ± 2°C) storage. The biochemical, microbial, andsensory quality were analyzed by association of official analytical chemists method, plate count, and QualityIndex method (QIM), respectively. Protein, lipid, and moisture content were found to decrease significantly(p < 0.05) over the study period. Nonetheless, the values of ash, total volatile base nitrogen, tri-methyl aminenitrogen, pH, and peroxide increased significantly (p < 0.05). After 28 days of frozen storage, the total bacterialload in tuna fish loins was reduced from 3.8 × 105 to 3.3 × 104 colony forming unit/g. Total coliforms reducedfrom 113 to 5 Most Probable Number (MPN)/g, fecal coliforms declined to undetectable level from 13 MPN/g,and total Salmonella sp. also decreased from 1 MPN/g to unnoticeable, respectively. Organoleptically tunaloins were found in excellent condition up to 14th days although remained acceptable up to 28th days of thestudy period. The present findings should that the skipjack tuna loins can be retained under an acceptable limitfor human consumption at frozen storage conditions up to 28th days.

Studies on the Effect of Vacuum Packaging on Some Quality Changes in Labeo Rohita During Frozen Storage Period.

This study was designed to investigate the influence of vacuum packaging on nutritional, chemical and microbial parameters of rohu fillets during frozen storage. Quality assessment of vacuum packaging rohu for up to 1 month at -12°C was done by the monitoring of nutritional quality, free fatty acids (FFA), thiobarbituric acid (TBA), pH and expressible moisture (EM). Results showed that free fatty acid, primary and secondary oxidation products, expressible moisture and pH value of vacuum packaging samples were significantly lower than those in control samples (p<0.05). Results indicated that vacuum packaging was effective in reduce lipid oxidation and increased shelf life of rohu frozen fillets. Similarly the microbial load of vacuum packaging samples was significantly lower as compared to control samples. Thus the employment of vacuum packaging alone or in combination with other protective strategies is recommended.

Comparison of fatty acid content of fresh and frozen fillets of rainbow trout (Oncorhynchus mykiss) Walbaum

The aim of this study was to evaluate and compare the percentage content of fatty acids (FA) of 54 rainbow trout fresh and frozen fillets. Frozen fillets were stored at -15ºC for 45 and 90 days. Saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA), omega-6 (n-6) and omega-3 (n-3) fatty acids were determined by gas chromatograph coupled to mass spectrometry. The results indicated that during frozen storage, SFA and MUFA content increased by 32.63 and 9.25%, respectively, while PUFA content decreased by 25.3%, n-6 by 12.4% and n-3 by 32.55%. These changes were more significant (P ≤ 0.05) during the first 45 d of storage. It was concluded that the frozen storage had a negative impact on meat quality of rainbow trout due to the reduction of PUFA, n-3/n-6, polyene index and PUFA/ SFA and the increase of the SFA, and atherogenic and thrombogenic indexes, which meant a substantial loss of nutritional value in the fillets of rainbow trout.

Effect of refrigeration and frozen storage on the campylobacter jejuni recovery from naturally contaminated broiler carcasses

Campylobacter jejuni is the most common thermophilic Campylobacter associated with human enteritis in many countries. Broilers and their by-products are the main sources for human enteritis. Refrigeration and freezing are used to control bacterial growth in foods. The effect of these interventions on survival of Campylobacter jejuni is yet not quite understood. This study evaluated the effect of storage temperature on the survival of C. jejuni in chicken meat stored for seven days at 4ºC and for 28 days at -20ºC. The influence of selective enrichment on recovery of Campylobacter was also evaluated. Thirty fresh chicken meat samples were analyzed and 93.3 percent was contaminated with termotolerant Campylobacter spp. with average count of 3.08 Log10 CFU/g on direct plating. After refrigeration, 53.3 percent of the analyzed samples tested positive for Campylobacter and the average count was 1.19 Log10 CFU/g. After storage at -20ºC, 36.6 percent of the samples were positive with a verage count of 0.75 Log10 CFU/g. C. jejuni was detected after enrichment, respectively, in 50 percent of the fresh, 36.7 percent of the refrigerated and 33.3 percent of the frozen meat samples analyzed. No difference was detected for the recovery of C. jejuni from fresh, refrigerated or frozen samples after selective enrichment, showing that this microorganism can survive under the tested storage conditions.

Influence of washing and frozen storage on the myofibrillar protein fraction in sardine mince flesh

El almacenamiento congelado de especies pesqueras, como la sardina, resulta en cambios significativos en sus propiedades funcionales las cuales determinan su tiempo de vida en almacenamiento. La pulpa de sardina se caracteriza por un alto contenido de grasa, músculo oscuro, y proteínas sarcoplasmáticas que inhiben la formación de geles a base de esta pulpa. Aplicando tratamiento de lavado a la pulpa de sardina se remueven compuestos indeseables para la preparación de productos a base de esta pulpa y a la vez aumentando su tiempo de vida en anaquel. El objetivo del presente estudio fue evaluar el efecto del almacenamiento en congelación a –30°C sobre la fracción de las proteínas miofibrilares de la pulpa de sardina tratada con soluciones al 0,5 por ciento de bicarbonato de sodio. Lotes de pulpa de sardina se le aplicó tratamiento de lavado con una solución de bicarbonato de sodio al 0,5 por ciento y luego centrifugadas a 300 rpm por 15 min. para la eliminación del agua remanente. Lotes de 100 gr. fueron empacados en bolsas de polipropileno y almacenadas a –30°C y analizadas cada 30 días durante150 días. Las proteínas nmiofibrilares fueron extraídas con buffer fosfato (tris HCl, KCl, EDTA, pH 7,6), y evaluadas por la técnica de electroforesis, SDS-PAGE. Las bandas de las diferentes proteínas y sus productos de degradación fueron analizadas y digitalizadas utilizando un Gel Doc 2000 y un programa Quality One 4.1.1 de Bio-Rad. Las principales bandas y sus productos de degradación fueron identificados por comparación de estos contra un estándar de peso molecular. A los 60 días se observó el comienzo del deterioro de las proteínas miofibrilares con pesos moleculares aparentes entre 220 y 65KD, y la formación de agregados moleculares de alto peso molecular. A los 120 días este deterioro se hace más pronunciado apareciendo gran cantidad de bandas de bajo peso molecular, péptidos, los cuales incrementan a medida que transcurre el tiempo de almacenamiento congelado...

Frozen storage of fish species, such as sardine, result in detrimental changes in functional properties that determine storage life. Sardine meat is characterized by high fat content, dark meat, and sarcoplasmic proteins that inhibit gel formation. Washing mince flesh with solutions such as sodium bicarbonate is very effective for removing undesirable components. The objective of this research was to study the effects of frozen storage at -30°C in the myofibrillar protein fraction of sardine mince flesh washed with 0.5% sodium bicarbonate solution. Samples of sardine-minced flesh were washed three times with a 0.5% of sodium bicarbonate solution and centrifuged at 3000 rpm for 15 minutes. These samples were divided in lots of 100 g. packed in plastic bags and stored at -30°C, and analyzed every 30 days for 150 days. The myofibrillar proteins were extracted using a phosphate buffer (tris HCl, KCl, EDTA, pH 7.6), and evaluated by SDS-PAGE. The bands were analyzed and digitalized with a Gel Doc 2000 and Quality One 4.1.1 by Bio-Rad. The main bands of myofibrillar protein were identified by comparison of these against a prestained molecular weight standard. After 60 days there was deterioration of the myofibrillar protein fraction with apparent molecular weight between 220 and 65KD, and the formation of molecular aggregates at high molecular weight occurred. After 120 days due to myofibrillar protein deterioration, protein and peptides with low molecular weight were formed and increasing throughout frozen storage. Understanding the mechanism involved in the deterioration of the mince flesh during frozen storage we would enable to help the establishment of quality parameters and ability to predict storage life for that product.

Estabilidad de filetes de sardina (Sardinella aurita) en almacenamiento congelado a -18ºC / Stability of Sardine Fillets (Sardinella aurita) under Frozen Storage at -18°C

Los cambios físicos, químicos y sensoriales fueron evaluados en filetes de sardina (Sardinella aurita), almacenados en congelación a -18°C por seis meses. Se tomaron muestras mensualmente con el propósito de determinar: pH, color (L, a y b), líquido exprimible (LE), solubilidad de proteínas solubles en soluciones salinas (SPs), ácido tiobarbitúrico (TBA), ácido láctico, perfil de ácidos grasos, humedad y evaluación sensorial. En este estudio el tiempo de almacenamiento mostró diferencias significativas (P < 0,05) con respecto a: color (L, a y b), evaluación sensorial, SPs y LE. La evaluación sensorial resultó ser el parámetro más idóneo para medir la estabilidad de los filetes congelados, los cuales mostraron un excelente grado de frescura, hasta el segundo mes de almacenamiento a partir del cual comienza a decrecer, pero conservando buenas condiciones sensoriales hasta el quinto mes. Al sexto mes se manifestaron alteraciones en el color del músculo, con la aparición de manchas amarillas, debido posiblemente a la oxidación de lípidos. Estos cambios sensoriales fueron confirmados por el índice de TBA, el cual se incrementó de 0,024 (Ab.Und/g), hasta 0,22 al sexto mes. La frescura inicial de las sardinas crudas, su bajo contenido de grasa y una correcta manipulación, fueron los factores que influyeron en la estabilidad del producto final.

Physical, chemical and sensorial changes were evaluated in sardine (Sardinella aurita.) fillets under frozen storage at -18°C for six months. Samples were taken monthly in order to evaluate: pH, colour (L,a, and b), water binding capacity (WBC), solubility of proteins in saline solutions (SPs), thiobarbituric ácid test (TBA), lactic acid, fatty acid profile, moisture and sensory evaluation. In this research the storage time shows significant differences (P < 0.05) with: colour (L,a and b), sensorial evaluation, SPs and WBC. Sensorial evaluation was the most suitable parameter in measurement frozen fillets stability. Fillets showed an excellent grade of freshness, until second month of frozen storage. After that, quality decrease, but also can reach until fifth month, with good sensorial conditions, meanwhile at sixth month, muscle colour was alterate with yellow spots, maybe due by lipid oxidation. These sensorial changes were confirmed by TBA index, which increase from 0.024 (Ab.Und/g) at the beginning of this experience, until 0.22 al sixth month. The initial freshness of raw sardine, the low fat level (2.5%), and good manipulation were important factors that influence in the stability of the end product.