Effect of freezing under electrostatic field on selected properties of an agar gel

Effects of electric and magnetic field on freezing characteristics of gel model food

The novel freezing technologies including electrostatic field assisted freezing (EF), static magnetic field assisted freezing (MF), electrostatic field combined with static magnetic field assisted freezing (EMF) were conducted on model food to facilitate comparing their application effect. The results show that the effect of EMF treatment was best, which significantly changed the freezing parameters of the sample. Compared with the control, the phase transition time and total freezing time were shortened by 17.2% and 10.5%, respectively; the proportion of the sample free water content detected by low-field nuclear magnetic resonance was significantly decreased; the gel strength and hardness were significantly improved; the protein secondary and tertiary structures were better maintained; the ice crystal area was reduced by 49.28%. Inverted fluorescence and scanning electron microscopic results indicated that the gel structure of EMF treatment samples was better than MF and EF. MF was less effective in maintaining the quality of frozen gel model.

Advances in prepared dish processing using efficient physical fields: A review

Prepared dishes are increasingly popular convenience food that can be eaten directly from hygienic packaging by heating. Physics field (PF) is food processing method built with physical processing technology, which has the characteristics of high efficiency and environmental safety. This review focuses on summarizing the application of PFs in prepared dishes, evaluating and comparing PFs through quality changes during processing and storage of prepared dishes. Currently, improving the quality and extending the shelf life of prepared dishes through thermal and non-thermal processing are the main modes of action of PFs. Most PFs show good potential in handing prepared dishes, but may also react poorly to some prepared dishes. In addition, the difficulty of precise control of processing conditions has led to research mostly at the laboratory stage, but as physical technology continues to break through, more PFs and multi-physical field will be promoted for commercial use in the future. This review contributes to a deeper understanding of the effect of PFs on prepared dishes, and provides theoretical reference and practical basis for future processing research in the development of various enhanced PFs.

Freezing characteristics and relative permittivity of rice flour gel in pulsed electric field assisted freezing

This study investigated the effect of pulsed electric field assisted freezing treatment on the freezing characteristics of rice flour gel under output voltages varying from 0 to 25 kV. The results indicated that by applying a pulsed electric field, the phase change time decreased. Scanning electron microscopy images indicated that pulsed electric field treatment led to the formation of rounder and smaller ice crystals. For further understanding and quantifying the interaction between rice flour gel and a pulsed electric field, the relative permittivity of rice flour gel with and without the addition of salt was measured between 100 and 3100 kHz and -20 and 20 °C. Relative permittivity increased with decreasing frequency or increasing temperature, and sharp variation was observed during the phase transition period. In addition, salt was proved to be an effective additive for increasing relative permittivity.

Biologically Derived Gels for the Cleaning of Historical and Artistic Metal Heritage

In the general global rise of attention and research to seek greener attitudes, the field of cultural heritage (CH) makes no exception. In the last decades, an increasing number of sustainable and biologically based solutions have been proposed for the protection and care of artworks. Additionally, the safety of the target artwork and the operator must be kept as core goals. Within this scenario, new products and treatments should be explored and implemented in the common conservation praxes. Therefore, this review addressing metal heritage is aimed to report biologically derived gel formulations already proposed for this specific area as reliable tools for cleaning. Promising bio-gel-based protocols, still to be implemented in metal conservation, are also presented to promote their investigation by stakeholders in metal conservation. After an opening overview on the common practices for cleaning metallic surfaces in CH, the focus will be moved onto the potentialities of gel-alternatives and in particular of ones with a biological origin. In more detail, we displayed water-gels (i.e., hydrogels) and solvent-gels (i.e., organogels) together with particular attention to bio-solvents. The discussion is closed in light of the state-of-the-art and future perspectives.

Supercooling preservation technology in food and biological samples: a review focused on electric and magnetic field applications

Freezing has been widely recognized as the most common process for long-term preservation of perishable foods; however, unavoidable damages associated with ice crystal formation lead to unacceptable quality losses during storage. As an alternative, supercooling preservation has a great potential to extend the shelf-life and maintain quality attributes of fresh foods without freezing damage. Investigations for the application of external electric field (EF) and magnetic field (MF) have theorized that EF and MF appear to be able to control ice nucleation by interacting with water molecules in foods and biomaterials; however, many questions remain open in terms of their roles and influences on ice nucleation with little consensus in the literature and a lack of clear understanding of the underlying mechanisms. This review is focused on understanding of ice nucleation processes and introducing the applications of EF and MF for preservation of food and biological materials.

How effective is freezing at killing Anisakis simplex, Pseudoterranova krabbei, and P. decipiens larvae? An experimental evaluation of time-temperature conditions

The consumption of raw or inadequately cooked marine fish can lead to several disorders caused by the ingestion of viable anisakid nematodes. Although anisakid larvae can be killed by subzero temperatures, making freezing an important control measure for this potential health hazard, these parasites can survive freezing under some conditions. Therefore, the aim of the present study was to experimentally evaluate the time-temperature conditions needed to kill Anisakis simplex and Pseudoterranova spp. The effectiveness of freezing was tested on two species of fish: cod, Gadus morhua from the North Atlantic, and herring, Clupea harengus membras from the southern Baltic Sea. Samples, which comprised skinless fillets of cod (n = 40) with visible parasites and whole herring (n = 240), were separately frozen at − 15, − 18, or − 20 °C for 24 h, or at − 20 °C for 48 h in the single-compressor freezer and at − 20, − 25, or − 35 °C for 24 h in the double-compressor freezer. After thawing, parasites were stained with malachite green and examined under the microscope for viability. All A. simplex and Pseudoterranova spp. larvae in cod fillets died at a temperature of − 15 °C or lower. However, freezing did not kill all the A. simplex larvae in whole herring: spontaneous movement of these parasites was observed in samples stored in the single-compressor freezer at − 15, − 18, and − 20 °C over 24 h. Our results demonstrate that the freezing procedure must consider both the capability of the freezing device and the nature of the fish product to ensure consumer safety.

Influence of uniform magnetic field on physicochemical properties of freeze-thawed avocado puree

3D magnetic fields have the potential to improve the quality of food after freeze-thawing.