Magnetic freezing is nowadays established as a commercial reality mainly oriented towards the food market. According to advertisements, magnetic freezing is able to generate tiny ice crystals ...throughout the frozen product, prevent cell destruction, and preserve the quality of fresh food intact after thawing. If all these advantages were true, magnetic freezing would represent a significant advance in freezing technology, not only for food preservation, but also for cryopreservation of biological specimens such as cells, tissues, and organs. Magnetic fields (MFs) are supposed to act directly on water by orientating, vibrating, and/or spinning molecules to prevent them from clustering and, thus, to promote supercooling. However, many doubts exist about the real effects of MFs on freezing and the science behind the potential mechanisms involved. To provide a basis for extending the understanding of magnetic freezing, this paper presents a critical review of the materials published in the literature up to now, including both patents and experimental results. After examining the information available, it was not possible to discern whether MFs have an appreciable effect on supercooling, freezing kinetics, ice crystals, quality, and/or viability of the frozen products. Experiments described in the literature frequently fail to identify and/or control all the factors that can play a role in magnetic freezing. Moreover, many of the comparisons between magnetic and conventional freezing are not correctly designed to draw valid conclusions, and wide ranges of MF intensities and frequencies are unexplored. Therefore, more rigorous experimentation and further evidence are needed to confirm or reject the efficacy of MFs in improving the quality of frozen products.
Since the early 2000s, electromagnetic freezers have been sold all over the world. According to the manufacturers, the oscillating magnetic fields (OMFs) applied by these devices are capable of ...avoiding ice damage in frozen foods. To assess the effectiveness of OMFs in preserving food quality, we froze crab sticks in a commercial electromagnetic freezer, both with (<2 mT, 6–59 Hz) and without OMF application. Crab sticks were also frozen in a conventional freezer, both with static- and forced-air conditions, to compare electromagnetic freezing with conventional methods. After 24 h and 1, 3, 6, 9, and 12 months of storage, we did not find any effect of the OMFs on the drip loss, water-holding capacity, toughness, and whiteness of the crab sticks frozen in the electromagnetic device. Moreover, no advantage of electromagnetic freezing over air-blast freezing was detected at the conditions tested. More experiments at larger magnetic field strength and wider frequency ranges are needed to have a complete view of the potential effects of OMFs on food freezing.
•Crab sticks were frozen in both an electromagnetic and a conventional freezer.•Several quality attributes were assessed after 0–12 months of frozen storage.•Electromagnetic freezing failed to retain the quality of fresh crab sticks unaltered.•Oscillating magnetic fields produced no effect on the quality of the frozen samples.•No advantage of electromagnetic freezing over air-blast freezing was observed.
Objective
As shellfish preservation is still nowadays a challenge for the food industry, in this paper, the effectiveness of hyperbaric storage in preserving Atlantic razor clams (
Ensis directus
) ...was evaluated both at low (HS-LT) and at room temperature (HS-RT).
Methods
The study was carried out in two phases. In the first phase, razor clams were stored at different pressure levels, both at 5 °C and 20 °C, for 7 days to identify the most efficient storage pressure at both temperatures. Then, in the second phase of the study, HS-LT and HS-RT experiments were performed at these conditions for 14 days to compare the effectiveness of both methods.
Results
Microbial analysis after storage showed that, at 5 °C, a minimum pressure of 50 MPa was needed to prevent microbial growth in the samples, while 75 MPa were required at 20 °C. In the second phase of the study, results revealed that both HS-LT (50 MPa/5 °C) and HS-RT (75 MPa/20 °C) extended the microbial shelf-life of the razor clams to, at least, twice that achieved in conventional refrigeration, but quality decline was larger in the samples stored at 75 MPa and 20 °C.
Conclusions
HS-LT resulted more effective than HS-RT for the preservation of razor clams.
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•Methylcellulose or silicon emulsions reduced pork fat digestibility.•Silicon lost its reducing effect on fat digestibility in presence of methycellulose.•Flow behavior index can be a ...predictive marker of the extent of lipolysis.•Methylcellulose or silicon emulsions could replace pork lard in animal products with potential health benefits.
During the last decade, the consumption of animal saturated fat has been associated with an increased risk of chronic disease. Experience shows that changing the dietary habits of the population is a complicated and slow process, so technological strategies offer new possibilities for the development of functional foods. The present work is focused on studying the impact of using a food-grade non-ionic hydrocolloid (methylcellulose; MC) and/or the inclusion of silicon (Si) as a bioactive compound in pork lard emulsions stabilized with soy protein concentrate (SPC), on the structure, rheology, lipid digestibility and Si bioaccesibility during in vitro gastrointestinal digestion (GID). Four emulsions (SPC, SPC/Si, SPC/MC and SPC/MC/Si) were prepared with a final biopolymer (SPC and/or MC) concentration of 4% and 0.24% Si. The results showed a lower degree of lipid digestion in SPC/MC compared with SPC, specifically at the end of the intestinal phase. Moreover, Si partially reduced fat digestion only when incorporated into the SPC-stabilized emulsion, while this effect was lost in SPC/MC/Si. This was probably due to its retention inside the matrix emulsion, which resulted in lower bioaccesibility than in SPC/Si. Additionally, the correlation between the flow behavior index (n) and the lipid absorbable fraction was significant, suggesting that n can be a predictive marker of the extent of lipolysis. Concretely, our results revealed that SPC/Si and SPC/MC can be used as pork fat digestion reducers and thus, they can replace pork lard in the reformulation of animal products with potential health benefits.
Due to its characteristic aroma and flavor, puff pastry (PP) prepared with butter is more accepted than that made with margarine, yet a high saturated fat consumption is associated with ...cardiovascular disease. This work studies the potential of olive-pomace oil (OPO) as main ingredient of PP margarines together with different organogelator agents to imitate the technological properties of a commercial fatty preparation (CFP). Rheological and textural properties were measured in all formulated margarines (FM) and, additionally, thermal and microstructural properties, and fatty acid (FA) profiles were analyzed in some selected FM. The different FM had viscous modulus (
″) and loss factor (tan
) values lower than those of CFP, thus reflecting a different viscoelasticity and plasticity. The crystallization and melting temperatures of FM were also different from those of CFP, indicating the presence of a dissimilar polymorphic fat-crystal structure. Nevertheless, the FM containing an oleogel prepared with 5% beeswax and OPO was more similar to CFP. The FA profile of CFP and FM, with 80% polyunsaturated fatty acids (PUFA) and 60% oleic acid, is healthier than that of a PP commercial butter (CB), evidencing that, although improvements in margarine plasticity are still necessary, OPO is technologically viable to produce healthier PP margarines.
New Alternatives in Seafood Restructured Products Moreno, Helena M.; Herranz, Beatriz; Pérez-Mateos, Miriam ...
Critical reviews in food science and nutrition,
01/2016, Letnik:
56, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A general overview, focusing on new trends in the different techniques used in restructured seafood product processing has been described in this work. Heat-induced gelation has been more widely ...studied in scientific literature than cold gelation technology. This latter technology includes the use of hydrocolloids (alginates and glucomannan) or enzymes (microbial transglutaminase) for making both raw and cooked restructured products. In restructuration processes, fortification processing with some functional ingredients is studied, giving as a result extra value to the products as well as increasing the variety of new seafood products. The process of alleviating heavy metals and organic pollutants from the raw material used has also been reviewed in the present paper.
► Ultrasound/conventionally blanched carrots had similar sensory quality after drying. ► The pattern of vitamin C losses is mainly attributed to different blanching conditions. ► ChemSensor allowed ...differentiation of samples with similar composition/processing.
Vitamin C content and sensorial properties have been evaluated in air-dried carrots previously subjected to different ultrasound (US) or conventional blanching pretreatments. In addition, mass spectral fingerprints obtained by the Headspace ChemSensor System have been evaluated for the first time for classification of carrots according to their processing. Conventional blanching treatments at high temperature gave rise to carrots with retention of vitamin C in the range 37.5–85%, whereas carrots blanched conventionally at 60°C and by US-probe at temperatures up to 60 and 70°C showed vitamin C retention values lower than 4%. Regarding sensorial analysis of rehydrated carrots, US-pretreated samples presented acceptable quality, and no statistically significant differences with respect to conventionally blanched carrots, were detected. In spite of this, differentiation of samples processed under comparable intensity conditions and/or with similar composition was possible from their mass spectral fingerprints after chemometric data analysis.
The structure-function relationship of composite films obtained from soybean-protein isolate (SPI) and cod gelatin was studied. Films with different ratios of SPI:gelatin (0, 25, 50, 75, 100% w/w) ...and plasticized by a mixture of glycerol and sorbitol were prepared by casting. Regardless of the soybean-protein concentration, the thickness and water-vapor permeability of the composite films diminished significantly as compared to pure-gelatin films. The formulation containing 25% SPI: 75% cod-skin gelatin had the maximum force at the breaking point, which was 1.8-fold and 2.8-fold greater than those of 100% gelatin and 100% SPI films, respectively. Moreover, this formulation offered high percent-deformation values lower than those of gelatin but higher than all other films containing SPI-, and the same relatively low water-vapor permeability as the 100% SPI film. While all the films exhibited high water solubility, a slight reduction in film solubility and soluble protein was observed with increasing SPI concentration. Differential-scanning calorimetry analyses revealed that gelatin was completely denatured in all films, while soy proteins largely maintained their native conformation. Analysis by fourier-transform–infrared spectroscopy revealed that the presence of 25% SPI produced gelatin conformational changes, self-aggregation of gelatin chains, and intermolecular associations via C
O bonds between gelatin and SPI proteins. All films were translucent in appearance, but the yellowish color increased with increasing proportions of the soybean proteins.
This study explores the influence of carboxymethylcelullose (CMC) and methylcelullose (MC), added by simultaneous (sim) and sequential (seq) emulsification methods, on the structure, rheological ...parameters and in vitro lipid digestibility of pork lard O/W emulsions stabilized by soy protein concentrate (SPC). Five emulsions (SPC, SPC/CMC-sim, SPC/CMC-seq SPC/MC-sim, SPC/MC-seq) were prepared in vitro. The presence of CMC and MC, and the stage of incorporation affected the emulsion microstructure. In the SPC emulsion, lipid droplets were entrapped by a protein layer that was thicker when MC was added, providing greater resistance against environmental stresses during gastrointestinal digestion. At 37 °C, CMC incorporation produced a structural reinforcement of the SPC emulsion, whereas MC addition did not affect the network rigidity, although a delaying effect on the crossover temperature was observed, which was more evident in SPC/MC-seq. The presence and stage of CMC and MC incorporation affected the rate and extent of lipolysis, with SPC/MC-seq presenting an inferior concentration of free fatty acids. The lower extent of lipolysis observed in SPC/MC-seq may be positive in the manufacture of animal fat products in which reduced fatty acid absorption is intended.
The effects of weak oscillating magnetic fields (OMFs ≤7 mT at 50 Hz) on freezing were studied in three systems of different complexity. To do so, ferric chloride solutions, lactate dehydrogenase ...(LDH), and minced hake muscle experimentally infected with
L3 were frozen with and without OMF application. OMFs did not affect freezing kinetics of either ferric chloride solutions or minced hake muscle. LDH activity,
mortality, and water-holding capacity of the hake muscle after thawing were not affected by OMF either. Further studies are needed to evaluate the effectiveness of stronger OMFs in a wider frequency range.
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