Quality evaluation of farmed whiteleg shrimp, Litopenaeus vannamei, treated with different slaughter processing by infrared spectroscopy

• Shrimp killed by ice water immersion presented better springiness and chewiness.
• Shelf life of shrimp is prolonged after ice water immersion processing.
• Quality differences of shrimp induced by pre-slaughter stress can be distinguished using IR.
• Quality differences are supposed to be related to structural changes of protein and fat.

The present study was to evaluate two slaughter processing methods (ice water immersion (T-1) and individual beheaded (T-2)) on whiteleg shrimp quality farmed in freshwater culture systems using attenuated total reflection infrared (ATR-IR) technology. In addition, the corresponding physical, chemical and microbial properties of shrimp samples were also determined. No significant differences were observed in pH, total volatile basic nitrogen (TVB-N), thiobarbutiric acid (TBA) and K value as well as the contents of moisture, crude protein, crude fat and ash between groups of T-1 and T-2. However, significantly higher springiness and chewiness (P < 0.05) were observed in T-1 as compared to those of T-2. As for the result of total viable counts (TVC), significantly lower value (P < 0.05) was shown in T-1 than that of T-2, indicating that the quality and shelf life of whiteleg shrimp killed by ice water immersion could be improved and prolonged. Furthermore, all the samples were successfully divided into two categories regarding the two slaughter methods by principal component analysis (PCA) according to the infrared spectra. By analysis of the regression coefficients of PLS-DA, it can be supposed that the quality differences of whiteleg shrimp with different slaughter processing are largely caused by structural changes of their protein and fat. All together, our results indicated that the springiness and chewiness of whiteleg shrimp with different processing could be correctly distinguished using infrared spectroscopy.