Yufeng Zou

Effect of Flavourzyme on proteolysis, antioxidant capacity and sensory attributes of Chinese sausage.

The objective of this study was to investigate the effect of Flavourzyme, at levels of 0 (control) 4, 8, 12, 16 and 20 LAPU/kg raw meat, on the proteolysis, antioxidant capacity and sensory attributes of Chinese sausage made at 50 °C for 48 h. Results showed that Flavourzyme addition in Chinese sausage accelerated protein degradation, which was reflected by the increase of non-protein nitrogen and appearance of new protein bands in both water-soluble and salt-soluble proteins. By adding Flavourzyme, texture profile analysis (TPA) parameters decreased significantly, and aroma, taste and texture scores were enhanced, respectively. The best sensory attributes were obtained at 8 and 12 LAPU/kg Flavourzyme dose. Besides, Flavourzyme addition enhanced antioxidant capacity, lowered water activity and TBARS values of Chinese sausage. Therefore, moderate Flavourzyme addition is a novel method with great potential to improve eating properties and storage stability of Chinese sausage.

Effect of a beating process, as a means of reducing salt content in Chinese-style meatballs (kung-wan): a physico-chemical and textural study.

Two different meat-cutting methods were used to prepare kung-wans in an attempt to produce low-salt products while retaining the same, or improved, textural and physicochemical properties of the standard high-salt formulation. The level of salt and the processing method significantly affected color, cooking yield, texture and changes in the secondary structures of proteins. Improved salt levels resulted in firmer texture. At the same salt levels, compared with chopping, the beating method resulted in higher L(*)-values, improved cooking yields and changes in the β-sheet content of the proteins, which resulted in an improved product with better texture. Using the beating process, the kung-wans prepared with 1% and 2% salt had similar L(*)-values, cooking yield and texture, and were better than those prepared by chopping with 2% salt. Overall, the beating process enabled lowering of the salt content, making the kung-wans more hard, brittle and elastic.

Effect of a beating process, as a means of reducing salt content in Chinese-style meatballs (kung-wan): a dynamic rheological and Raman spectroscopy study.

Chopping and beating processes were used as meat-cutting methods in preparing kung-wan to produce low-salt products while retaining or improving the emulsion stability, sensory evaluation, and physico-chemical properties of the standard high-salt formulation. Increased salt content improved emulsion stability and dynamic rheology. However, 3% salt content decreased the overall acceptance of kung-wan. Compared with the chopping process, beating resulted in higher emulsion stability, overall acceptance, and β-sheet content (P<0.05). Additionally, the beating process formed more compact and continuous structures at the same salt content. Kung-wan produced by beating with 1% and 2% salt had similar emulsion stabilities, sensory evaluation, and secondary structures (P>0.05). Therefore, this process allows reduction of salt content, suggesting that the kung-wan produced in this manner is healthier and has better texture.

Solubilisation of myosin in a solution of low ionic strength L-histidine: Significance of the imidazole ring.

Myosin, a major muscle protein, can be solubilised in a low ionic strength solution containing L-histidine (His). To elucidate which chemical constituents in His are responsible for this solubilisation, we investigated the effects of 5mM His, imidazole (Imi), L-α-alanine (Ala), 1-methyl-L-histidine (M-his) and L-carnosine (Car) on particle properties of myosin suspensions and conformational characteristics of soluble myosin at low ionic strength (1 mM KCl, pH 7.5). His, Imi and Car, each containing an imidazole ring, were able to induce a myosin suspension, which had small particle size species and high absolute zeta potential, thus increasing the solubility of myosin. His, Imi and Car affected the tertiary structure and decreased the α-helix content of soluble myosin. Therefore, the imidazole ring of His appeared to be the significant chemical constituent in solubilising myosin at low ionic strength solution, presumably by affecting its secondary structure.

Prooxidant Effects of the Combination of Green Tea Extract and Sodium Nitrite for Accelerating Lipolysis and Lipid Oxidation in Pepperoni during Storage

UNLABELLED The individual and interactive effects of green tea (GT) extract and sodium nitrite (NT) on lipolysis and lipid oxidation were investigated in pepperoni during processing and storage (4 °C). Pepperoni was treated with GT at concentrations of 0.02%, 0.05%, 0.1%, 0.2%, 0.5%; and NT from 0.003% to 0.015% in increments of 0.003%; and a combination of 0.05% GT and 0.009% NT (GT/NT). The pH, color, residual nitrite, fatty acid (FA), and 2-thiobarbituric acid reactive substances (TBARS) values were measured. The results showed inhibitory effects on TBARS value were concentration dependent. The largest effect was at 0.05% for GT and 0.009% for NT. Adding 0.05% GT significantly decreased (P < 0.05) the TBARS values but did not affect color values during storage. NT (0.009%) was more effective than GT (0.05%) for maintaining lower TBARS values (P < 0.05). Total fatty acids were not affected by 0.05% GT and 0.009% NT treatments. However, adding GT/NT showed a significant prooxidant effect (P < 0.05) in pepperoni, which accelerated lipolysis and lipid oxidation significantly (P < 0.05) during storage, with depletion of nitrite. This suggests that adding GT and an appropriate amount of NT into pepperoni could promote lipolysis and lipid oxidation during storage, as compared to NT alone. PRACTICAL APPLICATION When using GT extract as an antioxidant in industrial production of pepperoni, the interaction effect with NT should be considered, as it may lead to a prooxidant effect during refrigerated storage.

Effects of NaCl on water characteristics of heat-induced gels made from chicken breast proteins treated by isoelectric solubilization/precipitation

Effects of NaCl contents (0%, 0.5%, 1%, 1.5%, and 2%) on texture, water-holding capacities and microstructures of heat-induced gels made from chicken breast meat proteins isolated by isoelectric solubilization/precipitation (ISPC-gels) were investigated. The water characteristics during heating were also elucidated by low-field nuclear magnetic resonance T2 relaxometry. The ISPC-gels with increased NaCl content exhibited good texture and low cooking loss but high centrifugal loss. The amount of free water (T22 component) that was converted into immobilized water (T21 component) increased with NaCl addition in accordance with the decline in cooking loss. However, increased T21 values at 1.5% and 2% NaCl content indicated that water was weakly bound to the macromolecules and was highly mobile. These results were strongly corroborated by microstructure images that illustrated ISPC-gels containing 1% NaCl showed a continuous and dense structure with small pores and thin cross-linked strands, which had the lowest total water loss.

Applications of high pressure to pre-rigor rabbit muscles affect the water characteristics of myosin gels

Myosin was extracted immediately after high-pressure treatment (HP, 100-300MPa for 15 or 180s) to pre-rigor rabbit muscles (PRRMs) for evaluating the influences of HP-treatment on gel properties, using untreated muscles as Controls. Assessment of myosin yields, water-holding capacity (WHC), water mobility and distribution demonstrated that HP modified myosin before its extraction. Myosin gels subjected to HP at 100MPa 180s and 200MPa 15s had enhanced WHC compared with Controls. Also, the highest proportion of immobile-water was observed in myosin gels treated at 200MPa for 15s. HP-treatment of PRRMs affected their physicochemical properties as evidenced by alterations in tertiary, secondary conformations and rheological properties during subsequent heating. These modifications appear to induce various degrees of exposure of hydrophobic and sulfhydryl groups, resulting in different gelation rates. These alterations partly explain the various gel qualities obtained and indicate the potential of HP for pre-rigor muscles.