Effects of Storage Temperature and Preservative Treatment on Shelf Life of the Pond-Raised Freshwater Fish, Silver Perch (Bidyanus bidyanus)

Abstract

Sensory and microbiological characteristics of pond-raised freshwater silver perch (Bidyanus bidyanus) fish, during cold storage over a period of 25 days were evaluated. Whole fish (averaging 400 g each) were stored in cold storage rooms at either 0 to 2 degrees C, 5 degrees C, or 5 degrees C + potassium sorbate as a preservative. The organoleptic and hypoxanthine test results show that the treatment of potassium sorbate can slow the process of spoilage by about 5 days. Yet, the most important factor affecting the shelf life of these fish is the storage temperature. Keeping the fish at 0 to 2 degrees C can prolong the storage prior to spoilage by 10 days compared with those kept at 5 degrees C. These results obtained through organoleptic tests are corroborated by both the chemical (hypoxanthine and total volatile basic nitrogen) and to some extent by the physical (cosmos) tests. The initial total bacteriological counts were 5 x 10(2) CFU/cm2 for fish surface and <10(2) CFU/g for fish flesh, and these counts rose continuously, reaching about 106 CFU/g (0 to 2 degrees C) and 10(7) CFU/g (5 degrees C) in flesh and 10(7) to 10(8) CFU/cm2 on the surface by the end of the storage period. The addition of potassium sorbate led to a smaller increase in bacterial numbers, especially during the first 15 days. Bacterial composition fluctuated during storage. The initial load on the fish surface was predominantly mesophilic and gram positive and consisted mostly (80%) of Micrococci, Bacillus, and Corynebacterium. During the next 10 days, these bacteria were practically replaced by gram-negative flora comprised mostly of Pseudomonas fluorescens that rapidly increased with storage time and accounted for 95% after 15 days.

Incidence of indicator organisms, opportunistic and pathogenic bacteria in fish

“…Gonzalez-Rodriguez et al [26] found members of the Micrococcae family to be the third most abundant group of bacteria isolated from fresh water fish they studied. In addition to these, Gelman et al [27] also isolated Micrococcus species in 80% of the fish samples studied. The tilapia had more Staphylococcus than the catfish in this study though the handling and processing were very similar.…”

The Effects of Different Chilling Method and Storage Time on the Organoleptic Quality of Fresh Skipjack Tuna

“…Teknik penanganan ikan yang paling umum dilakukan untuk menjaga kesegaran ikan adalah penggunaan suhu dingin dan pembekuan. Selain itu, pada kondisi suhu rendah pertumbuhan bakteri pembusuk dan proses-proses biokimia yang berlangsung dalam tubuh ikan menjadi lebih lambat (Gelman et al, 2001). Penggunaan suhu rendah yang paling sering dan mudah dilakukan adalah pengesan.…”

Calidad microbiológica de la materia prima y el producto final del ceviche de tilapia y de camarón expendidos en el Área Metropolitana de San José, Costa Rica

“…Al respecto, ellos detallan que no existen normativas sanitarias para los ceviches, no obstante el recuento aerobio obtenido no es tan alto como el reportado a partir de los correspondientes alimentos crudos, justificándolo con base al marinado con ácidos de jugo de limón, naranja o vinagre al que se somete el ceviche (Flores et al 1996). En el presente trabajo, el efecto de la disminución del pH es claro en la disminución de las cargas bacterianas obtenidas, pero tampoco se puede dejar de lado la posible presencia de agentes antimicrobianos químicos, tipo sorbatos y el efecto benéfico de la refrigeración en el control de poblaciones (Gelman et al 2001). …”

“…y Enterococcus spp. presentes en los ceviches de tilapia y camarón a través de su almacenamiento a 4ºC por cinco días es importante destacar la poca variación que se da en estos, denotándose el efecto beneficioso de la refrigeración, de la acidez, así como la potencial presencia de agentes químicos en el control de poblaciones (Gelman et al 2001). …”