EFFECT OF pH AND TEMPERATURE ON JUMBO SQUID PROTEINS

Evaluation of the effect of pH (2 to 13) and temperature (0 to 50C) on functional properties of jumbo squid proteins was performed, followed by a 2  ×  3 factorial design for producing squid protein hydrolysates bearing useful functional properties. In particular, the effects of pH (8, 9 and 10) and temperature (30, 35, 40C) were evaluated. Alcalase and papain were tested on each treatment. The protein recovery, whippability and emulsifying capacity of the hydrolysates were evaluated. Almost 80% of the proteins were recovered in water-soluble form after hydrolysis with papain at pH 10 at the three temperatures. The highest values of whippability (245  ±  17.7%), foam stability (100%), emulsion-forming capacity (27  ±  0.97%) and stability (99.99  ±  8.8%) occurred with papain-produced hydrolysates. When squid protein was treated at 50C and pH 8, the highest whippability value (390.0  ±  0.1%) and foam stability (100%) were obtained when no enzyme was added.

PRACTICAL APPLICATIONS

This paper assesses how process variables, particularly temperature and pH, affect the functional properties of squid proteins. Making use of such process variables will produce more useful and efficient processes, as the application of a hydrolysis system. The processing of jumbo squid protein to obtain proteins bearing adequate functional properties would be an inexpensive way to provide added value to this marine resource and the production of a high-quality protein ingredient. These results hold promise for jumbo squid proteins as useful food ingredient because of their functional properties.     

PROTEIN SOLUBILITY AND PRODUCTION OF GELS FROM JUMBO SQUID

Solubility at several ionic strengths (0 to 1.0 M), pH (2 to 13) and gelling capacity of jumbo squid Dosidicus gigas muscle proteins were evaluated. Protein recovery was > 90% at pH 9 – 12. Autohydrolysis was evaluated and affected only sarcoplasmic proteins. Folding score was 5 on all gels. Strength was higher for thermal gels prepared from squid fin (50.2  ±  1.2 N) than that prepared from the mantle (23.4  ±  2.5 N). There was no significant difference in gel strengths from previously frozen (46.4  ±  7.5 N) and never-frozen samples (43  ±  5.5 N). Moisture, water drip and water-holding capacity were evaluated on thermal gels. There were significant differences between frozen and never-frozen samples. Results on solubility and gel forming capacity of the proteins from mantle and fin of jumbo squid suggest that these properties can provide additional value to this resource.

PRACTICAL APPLICATIONS

Jumbo squid is a rich source of high-quality protein. Obtaining sophisticated products would be an easy way to take advantage of the high-quality proteins in jumbo squid muscle. Knowledge of the functional properties of those proteins is needed to achieve this. The use of such properties, such as gel-forming capacity, which are similar to other proteins used in the food industry, will give jumbo squid added value. The results described here indicate that jumbo squid proteins may be useful as a food ingredient because of their solubility and gel-forming capacity.     

Ultrafast photon counting applied to resonant scanning STED microscopy

To take full advantage of fast resonant scanning in super‐resolution stimulated emission depletion (STED) microscopy, we have developed an ultrafast photon counting system based on a multigiga sample per second analogue‐to‐digital conversion chip that delivers an unprecedented 450 MHz pixel clock (2.2 ns pixel dwell time in each scan). The system achieves a large field of view (～50 × 50 μm) with fast scanning that reduces photobleaching, and advances the time‐gated continuous wave STED technology to the usage of resonant scanning with hardware‐based time‐gating. The assembled system provides superb signal‐to‐noise ratio and highly linear quantification of light that result in superior image quality. Also, the system design allows great flexibility in processing photon signals to further improve the dynamic range. In conclusion, we have constructed a frontier photon counting image acquisition system with ultrafast readout rate, excellent counting linearity, and with the capacity of realizing resonant‐scanning continuous wave STED microscopy with online time‐gated detection.     

TRYPSIN AND TRYPSIN INHIBITORS FROM PENAEID SHRIMP

Trypsin inhibitors from four species of shrimp, P. vannamei, P, monodon, P. stylirostris, and P. californiensis were characterized by test tube and electrophoretic assays. Inhibitors in the four phylogenetically related species showed different inhibitory capacity and specificity for orthologous trypsins. Inhibitors from P. californiensis showed a broader inhibitory capacity. Shrimp inhibitors inhibited cod trypsin, but not porcine or bovine trypsin, and subtilisin. The inhibitor from P. vannamei was stable at a wide range of pH and temperature. Results suggest that endogenous inhibitors for trypsin are ubiquitous in the penaeids.