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Studies on Rigor -mortis and Changes in Muscle Ph on the Drip Loss Under Different Storage Conditions of Rohu Fish (labeo Rohita)

M.A.R. Faruk
Department of fisheries Technology Bangladesh Agricultural University Mymensingh 2202 Bangladesh

M. Kamal
Department of fisheries Technology Bangladesh Agricultural University Mymensingh 2202 Bangladesh

M.A . Hossain
Department of fisheries Technology Bangladesh Agricultural University Mymensingh 2202 Bangladesh

M.R .A. Hossain
Fisheries Research Institute (FRI), Mymensingh-2202

M.l. Hossain
Department of fisheries Technology Bangladesh Agricultural University Mymensingh 2202 Bangladesh

Abstract/ Executive Summary:

The rigor -mortis of rohu fish (Labeo rohital was followed durmg storage in ice (0 C) for 24 h and at room temperature (22 ± 2°C) for 18 h. The duration of rigor was longer in fish stored in ice than that at room temperature. At room temperature, the fish attained a maximum rigor -index value of 60°1> in 6 h that lasted only for 1 h and then started to decrease. The fish relaxed completely in 18 h when it emitted a foul odour, for fish stored in ice, rigor index value showed a maximum of 82% in 10 h. The rigor at this level lasted for 3 h and then started to decrease, which indicated relaxation from rigor . The fish relaxed to only 35% after 24 h without marked changes in appearance and flavour. The rohu fish did not reach to full rigor (100%) in either storage condition. At room temperature, post-mortem fish muscle pH decreased more rapidly than at 0°C. The pH of the fish immediately after being killed was about 7.0. At room temperature muscle pH declined rapidly to a value of 6.15 in 18 h, while in ice stored fish muscle it decreased slowly to ultimate pH of 6.62 in 24 h. Two methods, cooking and centrifuging, were employed to determine the drip loss. Drip loss increased with the storage time but the amount of drip at room temperature was much higher than that at 0°C. The drip formation was directly related with the decrease in fish muscle pH. A considerable amount of protein was lost with the drip, but the loss was inversely related with the amount of drip.

Keywords: Rigor -mortis, pH, Drip loss, Rohu

Location: BAU, Fish farm , Mymensingh

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Carp fish

Objectives:

To investigate the effects of rigor -mortis and changes in muscle pH on the drip loss of rohu fish (Labeo rohita) under different storage conditions.

Methodology:

Four live rohu fishes (Labeo rohita) were obtained from the Bangladesh Agricultural University fish farm. After cranial spiking the fishes were immediately stored in ice (Q°C) and at room temperature (22 ± 2°C) . In both cases two fish samples were used, one for the measurements of rigor -index and pH, and the other for the measurement of drip loss. Measurement of Rigor-index: Rigor-index of the fish used as a measure of rigor tension, was determined. Briefly, the fish was placed on a horizontal table with half of its body . At selected time intervals, rigor index was calculated by the following equation: Rigor index (%)= (D₀-D/ D₀) X 100. pH value of muscle homogenate prepared by blending 10 g of fish muscle with 40 ml chilled water was measured by Corning pH meter. Measurement of Drip loss: An amount of 25g of fish muscle was taken during post - mortem storage, cut longitudinally into sections of uniform length and diameter , and wrapped in aluminum foil. Each muscle sample, weighed approximately 5 g, was covered with a fine meshed nylon net. The muscle samples were cooked in a beaker for 20 minutes at 100°C in a water-bath. The cooked muscle sample was removed from the beaker and weighed. The net-covered cooked-meat sample was then hung in stainless steel centrifuge tube and spun at 5000 RPM for 15 minutes. After centrifuging, the exudate released from the muscle was retained by decondition. The centrifuged sample was removed from the tubes with forceps and then reweighed to determine drip loss after centrifuge. The result was calculated as the percentage loss of the original weight of the muscle slice. The exudate was used for determination of protein concentration. The protein concentration of the drip was measured by biuret method.

Source of Information: Bangladesh J. Agril. Sci. 24(2): 43-49, July, 1997,ISSN 0379-4296

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Drip loss increased with the storage time but the amount of drip at room temperature was much higher than that at 0°C. The drip formation was directly related with the decrease in fish muscle pH. A considerable amount of protein was lost with the drip, but the loss was inversely related with the amount of drip.

Knowledge Management: Journal