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Post Mortem Changes in Mrigal Fish (cirrhina Mrigala) I. Studies on the Rigormortis and Changes in Muscle Protein at Various Storage Temperature

M.l. Hossain
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.A.R. Faruk
Department of Fisheries Technology Bangladesh Agricultural University Mymensingh-2202 Bangladesh

M.N. Islam
Department of Fisheries Technology Bangladesh Agricultural University Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

A study on rigor-mortis of mrigal fish (Cirrhina mrigala) was conducted at room temperature (25⁰C) and in ice (0⁰C). Rigor begins within 1 h after death in both conditions but duration of rigor was longer in iced fish than that kept at room temperature . The fish attained maximum rigor -index of 7 8% in 6 h at room temperature. The rigor index value remained same for another 1 h and then started to decrease. The fish relaxed completely after 18 h emitting a foul odour . For fish stored in ice rigor index was only 40% in 6 h and exhibited a maximum rigor index of 85% in 10 h. At this stage rigor lasted for 3 h and then started to decrease indicating relaxation from rigor. The fish relaxed to only 30% after 24 h without marked changes in appearance and flavour . The fish did not attain full rigor ( 100%) in either of the temperature condition. The fish muscle pH was about 7.0 immediately after death which declined rapidly to 6.10 after 18 h at room temperature, while pH in ice stored fish muscle declined slowly to 6. 60 after 18 h. The protein composition of ice stored mrigal white muscles was studied at different stages of rigor-mortis period. In pre-rigor stage 31 .5% sarcoplasmic , 59.00% myofibrillar, 7.3% alkali- soluple and 2.2% stroma protein were found. In in-rigor stage there were some changes in protein fraction such as 28.6% sarcoplasmic, 62 .5% myofibrillar, 6.7 % alkali- soluble and 1.3 % stroma protein. In post - rigor stage further changes were observed particularly in sarcoplasmic and myofibrillar protein where sarcoplasmic protein reduced to 25.4% and myofibrillar protein increased to 64.2 %.

Keywords: Rigor-mortis, Protein composition, Mrigal fish

Location: Bangladesh Agricultural University, Mymensingh

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Carp fish

Objectives:

To investigate the effect of temperature on the rigormortis and changes in muscle protein composition of mrigal fish (Cirrhina mrigala) at different stages of rigormortis during ice storage.

Methodology:

Six live specimens of mrigal (Cirrhina mrigala) (800-900 g in weight and 40-42 cm in length) were obtained from Bangladesh Agricultural University (BAU) fish farm. After cranial spiking the samples were packed in plastic bags and kept in ice (0⁰C) or at room temperature (25⁰C). In both cases two fish samples were used, one for the measurement of rigor index and pH; and the other for the measurement of protein composition from dorsal white muscle during pre-, in-, & post-rigor stages. Rigor index: "Rigor index" of the fish was measured essentially according to Bito et al. (1983) and used as a parameter of rigor tension. Briefly, the fish was placed on a horizontal table with half of its body (tail part) kept out of the table . At selected time intervals, rigor index was calculated by the following equation: Rigor index (%) = D₀ - D/ D₀ X 100. pH value of the muscle homogenate prepared by blending 10 g of fish muscle with 40 ml chilled water was measured by Corning pH meter. White muscle protein of each of the three fishes was fractionated by a 'procedure shown (Hashimoto et al., 1979) . All of the operations were performed at 3-4 ^oc as quantitatively as possible. The protein obtained after fractionation was determined by Biuret method and non- protein of TCA extract by Kjeldahl method (AOAC, 1980).

Source of Information: Bangladesh J. Agril. Sci. 25(1): 83-89, January, 1998

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Rigor begins within 1 h after death in both conditions but duration of rigor was longer in iced fish than that kept at room temperature . The fish attained maximum rigor -index of 7 8% in 6 h at room temperature. The rigor index value remained same for another 1 h and then started to decrease. The fish relaxed completely after 18 h emitting a foul odour . For fish stored in ice rigor index was only 40% in 6 h and exhibited a maximum rigor index of 85% in 10 h. At this stage rigor lasted for 3 h and then started to decrease indicating relaxation from rigor. The fish relaxed to only 30% after 24 h without marked changes in appearance and flavour . The fish did not attain full rigor ( 100%) in either of the temperature condition. The fish muscle pH was about 7.0 immediately after death which declined rapidly to 6.10 after 18 h at room temperature, while pH in ice stored fish muscle declined slowly to 6. 60 after 18 h. The protein composition of ice stored mrigal white muscles was studied at different stages of rigor-mortis period. In pre-rigor stage 31 .5% sarcoplasmic , 59.00% myofibrillar, 7.3% alkali- soluple and 2.2% stroma protein were found. In in-rigor stage there were some changes in protein fraction such as 28.6% sarcoplasmic, 62 .5% myofibrillar, 6.7 % alkali- soluble and 1.3 % stroma protein. In post - rigor stage further changes were observed particularly in sarcoplasmic and myofibrillar protein where sarcoplasmic protein reduced tu 25.4% and myofibrillar proein inc reased to 64.2 %.

Knowledge Management: Journal