Raman spectroscopy determines structural changes associated with gelation properties of fish proteins recovered at alkaline pH

Structural changes of alkali-treated rockfish protein isolate (AKPI) during frozen storage were elucidated using a Raman spectrometer and scanning electron microscope (SEM). The results were compared to conventional surimi (CS). No significant textural difference was noted between AKPI stored at pH 5.5 and 7.0. The strongest texture was found for AKPI frozen with cryoprotectants and CS, while the weakest texture was observed in AKPI frozen without cryoprotectants. SEM revealed the most discontinuity in gels of AKPI with no cryoprotectants and a more aggregated microstructure after storage at pH 5.5 than at neutral pH. Raman spectral analysis demonstrated refolding of AKPI by pH readjustment to 7.0, although the refolded structure was not identical to that before the pH shift. CS showed higher alpha-helix content (approximately 50%) than AKPI (approximately 20-30%). Frozen storage induced a decrease and an increase in the alpha-helix content of CS and AKPI samples, respectively. AKPIs were slightly less stable than CS during frozen storage.     

Controlling Lipid Oxidation and Volatile Compounds in Frozen Fried Fish Cake Prepared with Rice Bran Hydrolysate

ABSTRACT

Fried fish cakes formulated with (1) no antioxidant (control), (2) 1% rice bran hydrolysate (RBH), (3) 2% RBH, (4) 0.05% rosemary oil, and (5) 0.02% butylated hydroxyanisole/butylated hydroxytoluene (BHA/BHT) were investigated for their oxidation values following 0–9 freeze-thaw cycles. Both lipid oxidation and protein oxidation were significantly obstructed when RBH or BHA/BHT was used. RBH at 2% was equally effective as 0.02% BHA/BHT. Headspace solid phase microextraction (HS-SPME), which measures volatile compounds that determine lipid oxidation, demonstrated the effectiveness of RBH. The development of rancid volatile compound (i.e., hexanal) levels in fried fish cakes decreased during 0–9 freeze-thaw cycles. This study demonstrates that RBH is as an effective antioxidant comparable to commercial antioxidants (BHA/BHT) in frozen fried fish cakes. Consequently, RBH can be a consumer-friendly and natural antioxidant ingredient.     

Intention to adopt and diffuse innovative ultraviolet light C system to control the growth of microorganisms in raw milk among Thais Dairy Farmers

This research aims to investigate the factors affecting Thai dairy farmers’ intention to use ultraviolet C technology (UV‐C) to reduce the number of microorganisms in raw milk. The researcher applied the innovation and diffusion theory (IDT) and the technology acceptance model 2 (TAM2) to evaluate dairy farmer's intention. The 477 dairy farmers in the central part of Thailand were interviewed using questionnaires. The collected data were analyzed using multinomial logistic regression (MLR). It was found that the intention to adopt UV‐C can accurately predict the factors affecting the intention to use the technology based on the intention levels to create diffusion and promote acceptance. To increase the diffusion and acceptance of UV‐C, the perceived usefulness to increase the milk price was the major influenced factor to promote technology acceptance. Providing facilities for maintenance, the use of this innovation and reporting news about the benefits of new technology to create positive attitudes and confidence lead to the spread of technology driven by early adopters. The technology developers should consider and design technology compatible with existing systems. However, the collaboration of all related parties is also needed to encourage Thai dairy farmers to try the new technology and observe the actual results.