| Headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass (GC-MS) was used to detect and identify the volatile components in crucian carp (carasius auratus) muscle. Afterwards, the effects of acid-and alkali-aided processing on the removal of the fishy and muddy off-flavors were studied. Meanwhile, acid-and alkali-aided processing on the gel properties and storage stability at-18℃of crucian carp surimi were studied. This research would theoretically benefit the crucian carp surimi processing industry. The results were listed as follows:1. There were24volatile components identified in crucian carp muscle by using HS-SPME-GC-MS, including alcohols, aldehydes, ketones, hydrocarbons and other substances. Especially, alcohols, aldehydes, ketones were the mainly contributors on the fishy off-flavors in crucian carp muscle, such as1-octen-3-ol、hexanol、octanol、 hexanal、heptanal、octanal、nonanal、E,E-2,4-heptadienal、2,5-octanedione etc, while hydrocarbons and other substances were generally minor contributors to crucian carp flavors. GEO and MIB were the main substances of earthy components in crucian carp muscle, and their retention time were22.46min and16.26min, respectively.2. The minimum and maximum solubility of muscle protein from crucian carp was at pI=5.5and at pH=3.0(acid) and at pH=12.0(alkali), respectively. After been water washed, acid-aided and alkaline-aided processed, respectively, E,E-2,4-heptadienal of crucian carp muscle was completely removed, the the contents of hexanal were reduced from15.44%to9.31%,3.41%and3.37%, respectively, the contents of1-octen-3-ol were reduced from28.35%to14.21%,14.16%and13.00%, respectively, and the contents of hexanol were reduced from21.97%to4.33%,1.87%and1.87%, respectively. The contents of other volatile compounds were also decreased to some extent as well. In addition, the removal efficiency of GEO and MIB of crucian carp muscle were53.83%,71.03%and75.38%and22.63%,80.31%and82.87%respectively after three kinds of processing. Thereby, acid-and alkali-aided processing could be applied to reduce fishy and muddy off-flavors in crucian carp muscle. The volatile components of crucian carp muscle processed by water washing, acid-and alkali-aided methods can be differentiated by electronic nose. The PCA result demonstrated that volatile components of any two different samples were different, which was according with GC-MS. In conclusion, acid-and alkali-aided processes were more efficient to reduce fishy and muddy off-flavors in crucian carp muscle than water washing.3. After acid-and alkali-aided processing, the content of moisture, fat and ash of surimi was decreased, while the protein recovery yield was significantly increased. The SDS-PAGE results displayed that all treatments can decease the intense of myosin heavy chain (MHC), while actin bands of the surimi processed by alkali-aided treatment were more intense than those of the surimi with two other processess. The muscle proteins treated with acid-and alkali-aided processing showed different dynamic rheological properties compared with water washing muscle proteins. Both myofibrillar and sarcoplasmic proteins underwent denaturation after acidic and alkaline treatment, resulting in low protein extractability. Myosin and actin proteins were subjected to denaturation after acidic and alkaline treatment, which was shown in the absence of endothermic peaks. The surimi gels processed by acid-and alkali-aided treatments had lower whiteness, higher gel strength, hardness, gumminess, chewiness and water holding capacity than the surimi gel processed by water washing.4. Gel strength and hardness, chewiness, gumminess, adhesiveness, springiness, cohesiveness and resilience of surimi gels were slightly decreased and fat and protein oxidation were observed in the surimi processed by water washing, acid-and alkali-aided treatments during the storage at-18℃. Higher degree of fat oxidation was observed in water washing surimi than those of the two other treatments, but there was no significant difference in the level of protein oxidation. In all, surimi processed by acid-and alkali-aided treatments were more stable than water washing surimi during the storage period at-18℃. |
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