The Impact of High Pressure Processing and Pulsed Electric Field Processing on Physicochemical and Sensory Characteristics of Lamb Meat
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To better understand attitude of Chinese consumers towards lamb meat, perception and purchasing behavior of Chinese consumers for red meat were investigated. Chinese consumers placed importance on nutritional and health benefits of red meat like beef and lamb than high cholesterol of red meat like pork. It was also found that freshness was the most important factor affecting purchase intention. Most Chinese consumers purchased imported meat due to the safety concerns and the perceived high-quality attributes of imported meat. Safe food and organic labels were also important. Chinese consumers perceived red meat and meat products originating from New Zealand to be of high standard in terms of safety. In terms of purchasing intention, almost 60 % of consumers consumed offal, which provides an opportunity to the New Zealand meat industry to potentially export these by-products. Tenderness, freshness, colour and off-flavour attributes of sheep meat influenced consumer purchasing intention. Interestingly, consumption of lamb meat is seasonal, and was mainly consumed in winter and spring, in accordance to the philosophy of Chinese traditional medicine. Hot pot was the most favoured cooking method when consuming lamb meat, followed by stewing, pan-fried and barbecue methods. The Chinese consumers also did not value prime cuts like the loins and legs. The effects of HPP on the physicochemical properties and sensory characteristics of lamb meat cuts were investigated. Three lamb cuts (shank, loin and shoulder) were treated at 200 (14°C), 300 (21°C), 400 (28°C), and 600 (42°C) MPa. The results showed that lamb meat discoloration occurred when HPP was applied at high pressure levels (400MPa and 600MPa). TBARS value significantly increased as pressure increased from 200 MPa in loin cut, and 300 MPa with shoulder and shank cuts, compared to control. SFA and PUFA content significantly decreased in shank and shoulder cuts after HPP treatment at 200 MPa compared to control, whereas SFA and PUFA content significantly decreased in loin cut after HPP treatment at 300 MPa. Free amino acids content significantly increased in shank and loin cuts with pressure increase after 200 MPa, and in shoulder cuts after 400 MPa. Temporal dominance of sensations (TDS) results showed that HPP processing affected the temporal flavour profiles. Samples treated with HPP at high pressure levels (400 and 600 MPa) were associated with browned, livery and oxidized flavour. Results in the present study highlight the possibility of applying HPP processing to lamb meat. However factors like pressure levels applied and type of cuts used during processing are important considerations as they influence physicochemical and sensory properties of lamb samples. To gain better understanding on the effects of chilling and freezing prior to pulsed electric field processing (PEF) on volatile profile and sensory attributes of different cooked lamb muscles (i.e. shoulder, rib and loin) were investigated. Lamb samples were treated at electric field strength of 1–1.4 kV•cm−1, specific energy of 88– 109 kJ•kg−1, frequency of 90 Hz, pulse width of 20 μs and pulse number of 964. The results showed that prolonged storage time and frozen–thawed pre-treatment led to significant increases in volatile compounds due to lipid and protein oxidation. PEF also resulted in significant changes of volatile compounds in different meat cuts. Temporal dominance of sensations (TDS) showed that both storage and PEF treatment affected the temporal flavor of meaty and oxidized flavor attributes. Particularly, longer storage period was associated with oxidized flavor, while PEF treated samples were associated with browned, juicy, livery, and meaty flavour attributes. The effects of pulse electric field (PEF) processing combined with frozen storage on physicochemical properties and sensory characteristics of different lamb meat cuts were investigated. Seven lamb cuts (knuckle, rump, topside, shoulder shank, loin and rib) were treated at electric field strength of 1-1.4 kV.cm-1, specific energy of 88-109 kJ.kg-1, frequency of 90 Hz, pulse width of 20 µs and pulse number of 964. PEF processing and storage affected color stability that resulted from lipid oxidation and higher temperature generated from PEF processing. Chilled rump and shank cuts had less cooking loss after PEF processing and less PEF effects on cooking loss when applied on frozen-thawed meat. PEF treatments in combination with storage had significant effects on different chilled cuts. PEF treatments significantly affected the fatty acid profiles of all frozen-thawed cut compared to storage effects. PEF treatments significantly influenced free amino acid profiles of chilled rump, loin and rib cuts compared to storage effects. However, PEF treatments had less significant effects on the free amino acid profiles of frozen lamb meat cuts compared to storage that might be due to the higher electrical conductivities induced by freezing and thawing of meat, which results in inefficient field strength being applied to the meat that decreases proteolysis. Temporal dominance of sensations (TDS) results showed that both storage and PEF treatments affected the temporal flavor profiles of meaty and oxidized flavor attributes. A longer storage period was associated with oxidized flavor, while PEF treatment for all lamb cuts were associated with browned, juicy, livery, and meaty flavor attributes. PEF processing contributed to more oxidized flavor in PEF treated frozen–thawed rib cut stored for 7 days. These results imply that both application of PEF conditions and sample pre-treatment (chilled or frozen-thawed) should be considered when determining the effect of PEF processing on meat flavor in all seven lamb cuts.