Effects of Ultrasound-Assisted Vacuum Impregnation Antifreeze Protein on the Water-Holding Capacity and Texture Properties of the Yesso Scallop Adductor Muscle during Freeze-Thaw Cycles

Effect of ultrasound on mass transfer during vacuum impregnation and selected quality parameters of products: A case study of carrots

Many unit operations in the food industry are diffusional driven. These processes are usually very slow and difficult to handle for specific groups of raw materials. Vacuum impregnation (VI) is one example. Impregnating low-porous or densely-structured materials is problematic and often requires low pressure, which can negatively affect product quality and be expensive in energy consumption. This research aimed to evaluate ultrasound (US) as a factor in intensifying mass transfer and enhancing its effectiveness in the VI process. Experiments on impregnation enhanced with ultrasound applied at different stages of the process were carried out. Carrot, a difficult-to-process raw material, was impregnated with ascorbic acid as a mass transfer marker. The process's effectiveness and selected quality parameters were then analyzed. Ultrasound was found to have a positive influence on mass transfer during VI. The effects of ultrasound enhancement were different for particular processes, and depended on the stage of the application and duration of US exposure. The greatest increase in the tissue's ascorbic acid content (60% compared to the non-ultrasound-assisted process) was observed when ultrasound was applied continuously throughout the process. Applying ultrasound only during the relaxation (at atmospheric pressure) or aeration periods resulted in a similar effect - c.a. 20% increase in the marker's content. The smallest increase (10%) was observed when ultrasound was applied only during the vacuum period. Applying US did not result in any unfavorable color change. In most cases, pH decreased, which is favorable for the semi-product's stability. The carotenoid and phenolic compounds' content did not decrease. The results unequivocally indicate that ultrasound has great potential for use as a mass transfer accelerator in the VI process for low porosity materials. The effectiveness of the US is influenced not only by pressure but also by exposure duration. The synergistic effect observed using ultrasound-enhanced impregnation throughout the process confirmed this hypothesis.

Effect of antifreeze proteins on the freeze-thaw cycle of foods: fundamentals, mechanisms of action, current challenges and recommendations for future work

Freezing is widely used in food preservation, but if not carried out properly, ice crystals can multiply (nucleation) or grow (recrystallization) rapidly. This also affects thawing, causing structural damage and affecting overall quality. The objective of this review is to comprehensively study the cryoprotective effect of antifreeze proteins (AFPs), highlighting their role in the freeze-thaw process of food. The properties of AFPs are based on their thermal hysteresis capacity (THC), on the modification of crystal morphology and on the inhibition of ice recrystallization. The mechanism of action of AFPs is based on the adsorption-inhibition theory, but the specific role of hydrogen and hydrophobic bonds/residues and structural characteristics is also detailed. Because of the properties of AFPs, they have been successfully used to preserve the quality of a wide variety of refrigerated and frozen foods. Among the limitations of the use of AFPs, the high cost of production stands out, but currently there are solutions such as the use the production of recombinant proteins, cloning and chemical synthesis. Although in vitro, in vivo and human studies have shown that AFPs are non-toxic, their safety remains a matter of debate. Further studies are recommended to expand knowledge about AFPs, to reduce costs in their large-scale production, to understand their interaction with other food compounds and their possible effects on the consumer.

Effect of Different Thawing Methods on the Physicochemical Properties and Microstructure of Frozen Instant Sea Cucumber

To provide recommendations to users regarding which thawing method for frozen instant sea cucumbers entails lower quality losses, in this study we compared the water retention, mechanical properties, protein properties, and microstructures of frozen instant sea cucumbers post-thawing by means of different thawing approaches, including refrigerator thawing (RT), air thawing (AT), water immersion thawing (WT), and ultrasound-assisted thawing (UT). The results indicated that UT took the shortest time. RT samples exhibited the best water-holding capacity, hardness and rheological properties, followed by UT samples. The α-helix and surface hydrophobicity of WT and AT samples were significantly lower than those of the first two methods (p < 0.05). The lowest protein maximum denaturation temperature (Tmax) was obtained by means of WT. AT samples had the lowest maximum fluorescence emission wavelength (λmax). Based on these results, WT and AT were more prone to the degradation of protein thermal stability and the destruction of the protein structure. Similarly, more crimping and fractures of the samples after WT and AT were observed in the sea cucumbers’ microstructures. Overall, we observed that UT can be used to maintain the quality of frozen instant sea cucumbers in the shortest time.