Abstract
SUMMARYFreezing conditions affect fish muscle protein functionality due to its denaturation/aggregation. However, jumbo squid (Dosidicus gigas) muscle protein functionality remains stable even after freezing, probably due to the presence of low-molecular-mass compounds (LMMC) as cryoprotectants. Thus, water-soluble LMMC (<1 kDa) fraction obtained from jumbo squid muscle was evaluated by Fourier transform infrared spectrometry. From its spectra, total carbohydrates, free monosaccharides, free amino acids and ammonium chloride were determined. Cryoprotectant capacity and protein cryostability conferred by LMMC were investigated by differential scanning calorimetry. Fraction partial characterization showed that the main components are free amino acids (18.84 mg/g), carbohydrates (67.1 µg/mg) such as monosaccharides (51.1 µg/mg of glucose, fucose and arabinose in total) and ammonium chloride (220.4 µg/mg). Arginine, sarcosine and taurine were the main amino acids in the fraction. LMMC, at the mass fraction present in jumbo squid muscle, lowered the water freezing point to –1.2 °C, inhibiting recrystallization at 0.66 °C. Significant myofibrillar protein stabilization by LMMC was observed after a freeze-thaw cycle compared to control (muscle after extraction of LMMC), proving the effectiveness on jumbo squid protein muscle cryo- stability. Osmolytes in LMMC fraction inhibited protein denaturation/aggregation and ice recrystallization, maintaining the muscle structure stable under freezing conditions. LMMC conferred protein cryostability even at the very low mass fraction in the muscle.
Highlights
Cephalopods are the fastest growing aquatic population in the world harvested in fisheries due to the increasing demand for low-cost marine species
The low-molecular-mass compounds (LMMC) fraction (
Our result showed that the compounds present in the LMMC fraction inhibit recrystallization of water at 0.66 °C, contributing to the stabilization of muscle structure during temperature fluctuations under freezing conditions
Summary
Cephalopods are the fastest growing aquatic population in the world harvested in fisheries due to the increasing demand for low-cost marine species. Jumbo squid studies have been of great interest in the last years, mainly because this species tolerates environmental variations such as of pressure, temperature and dissolved oxygen [2] making it an interesting species. It has been observed that jumbo squid muscle structure and protein functionality remained stable during its frozen storage (–20 °C) and even after freeze-thaw cycles [5]. This stability may be attributed to the low-molecular-mass compounds (LMMC) present in the muscle of jumbo squid, product
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