Effect of high hydrostatic pressure processing on the lipid and protein characteristics of different lamb cuts
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HPP treatment is a popular non-thermal food processing technique, which can improve food quality and extend shelf-life. This study investigates the effects of high hydrostatic pressure processing (HPP) treatments of different lamb cuts on lipid oxidation, as well as fatty acid and free amino acid content. Eight different lamb cuts, tenderloin (T), rump (R), knuckle (K), inside (I), heel (H), Flat (F), eye of loin (E) and bolar (BL) were analysed. The cuts were treated at 600MPa (42°C), 400MPa (28°C), 300MPa （21°C）, 200MPa (14°C ) and 0MPa (7°C)for 5 seconds. In general, the higher levels of pressure (400MPa and 600MPa) employed resulted in higher oxidation values exceeding 0.5 mg MDA/kg in E, F, H and T cuts. On the other hand, lower pressures of 200MPa and 300MPa, resulted in oxidation values less than 0.5 mg MDA/kg for all cuts except for the K cut that had the highest oxidation value (0.522 mg MDA/kg) at 300 MPa.HPP treated R and H cuts had higher SFA and MUFA (P < 0.0001) content, and lower polyunsaturated fatty acid/saturated fatty acid ratio (P < 0.001) compared to control sample. Polyunsaturated fatty acid content was not significantly different to control for both cuts suggesting that little or no oxidation occurred. On the other hand, saturated fatty acid and monounsaturated fatty acid content were lower in HPP treated I, B, K, E, T and F cuts at all pressures compared to control samples. Polyunsaturated fatty acid content was also lower in HPP treated I (at all pressures), K (400 and 600 MPa), E (300 MPa) and T (600 MPa) cuts compared to control. The decrease in Polyunsaturated fatty acid was due to the decrease of mainly C18:1 n9 and C18:3 n3 fatty acids. Seventeen free amino acids, including 9 essential and 8 non-essential amino acids were identified in the eight lamb cuts. High pressure processing increased the total free amino acids composition significantly (P<0.05) compared to control at all pressures for almost all cuts except I and E cuts. As for the E cut, a significant decrease in total amino acids was observed at 600 MPa with a highly significant (P<0.0001) decrease in the essential amino acids leucine and isoleucine.