Cryoprotective effect of low molecular-mass nitrogen compounds on the myofibrillar protein of the jumbo squid (Dosidicus gigas) muscle

The study aimed to evaluate the low molecular-mass nitrogen compounds (LMMNC) arginine (Arg), taurine (Tau), and trimethylamine oxide (TMAO) (individually or their mixtures) cryostabilizing effect over jumbo squid (Dosidicus gigas) myofibrillar protein (JSMP) frozen at -20°C for 0, 30, and 90 days. Washed muscle (three times, 1:3, muscle:water) was lyophilized (sample). Washing water was ultrafiltrated (<1 kDa cut-off) and permeate lyophilized (<1 kDa fraction). LMMNC, Control+ (with <1 kDa fraction)] added at muscle concentration and control (washed-muscle only) were stored at -20 °C. Cryoprotective effect on JSMP was evaluated by differential scanning calorimetry, surface hydrophobicity (SoANS), solubility, and total-sulfhydryl (TS) content. Myosin thermal stability increased (P ≤ 0.05) in Control+ (43.6 ± 0.1), TMAO (44.3 ± 0.3), and Arg + TMAO (44.2 ± 0.9) compared to Con (42.6 ± 0.3) before freezing (day 0). At 90 days of storage, all TMAO-involved treatments and Control+ remained higher (p ≤ 0.05) than Control. Solubility increased (p ≤ 0.05) in Tau (11.2±0.0-12.8±0.1) and Arg+Tau (10.6±0.1-12.7±0.0) comparing day 0 vs. 90, respectively. LMMNC reduced SoANS (p ≤ 0.05, Arg+Tau+TMAO) throughout storage. LMMNC reduced (p > 0.05) TS in most treatments. LMMNC, especially Taurine and TMAO, protects JSMP from freezing denaturation, stabilizing its structure.