Microwave Thawing Research Articles

Effects of ultrasonics combined with far infrared or microwave thawing on protein denaturation and moisture migration of Sciaenops ocellatus (red drum)

The influence of ultrasonics combined with microwave thawing (UMT) and ultrasonics combined with far-infrared thawing (UIT) on the water migration and protein denaturation of red drum were studied. Five treatments were used: ultrasonics thawing (UT), microwave thawing (MT), far-infrared thawing (IT), UIT and UMT were used for thawing red drum filets. Moisture migration and protein aggregation were studied using nuclear magnetic resonance (NMR) and particle size, respectively. Raman spectra and fluorescence spectra were used to study the secondary and tertiary structure of protein. SEM was done to observe the fiber microstructure. The results showed that UMT and UIT can maintained protein stability more than other thawing methods and retained the fiber structure of the muscle. Besides, immobilized water in fiber bundles network also had no significant changes compared with fresh samples. Thus, ultrasonics combined with far infrared or microwave thawing were used to decrease protein denaturation and water migration during the thawing of Red drum fillets.

Cryopreservation as an alternative for conservation of Anacardium humile achene (Monkey nut)

The present study aimed to evaluate the possibility of using cryopreservation method for conservation of cajuzinho-do-cerrado achene (Anacardium humile). To accomplish this aim, the physiological quality of cryopreserved achenes was compared with the quality of samples stored under other conditions. The quality of cryopreserved achenes with different water contents was also evaluated to establish a water-content limit for seed-viability maintenance. Achenes with physiological maturity were stored in liquid nitrogen at -196 degreesC with the following water contents: 28 (initial content) 14, 12, 8 and 5% moisture content (mc). Subsequently, the achenes were subjected to 3 thawing methods: slow/gradual, fast and microwave thawing. Achenes were also subjected to different six conservation methods: cryopreservation in liquid nitrogen (LN) at -196 degreesC, cryopreservation using 10% cryoprotectants (Dimethyl sulfoxide (DMSO) or Glycerol), 10 degreesC biochemical oxygen demand (BOD) incubator, -80 degreesC ultra-low freezer and room temperature (25 degreesC +-3), with testing after storage in these environments for 5 and 10 months. The treatment effect on achene, physiological quality was assessed by seed germination (percentage) and vigour (germination speed index, electrical conductivity and root and shoot length). The results showed that reduction in the water content considerably reduced the germinating potential of 'Anacardium humile' achenes for cryopreservation. Conversely, the thawing methods had no effect on the physiological quality of cryopreserved achenes; thereby, allowing the choice of the most practical thawing method (microwave). We also concluded that cryopreservation in liquid nitrogen may be used as a viable alternative for conservation of 'Anacardium humile' achene.

Effects of magnetic nanoparticles plus microwave on the thawing of largemouth bass (Micropterus salmoides) fillets based on iTRAQ quantitative proteomics

The iTRAQ-based quantitative proteomic strategy was used to reveal the effects of magnetic nanoparticles plus microwave thawing (MNPMT) on the largemouth bass fillets quality. A total number of 47 proteins were identified as differentially abundant proteins (DAPs) in fillets treated by microwave thawing (MT), while 13 DAPs were in MNPMT. Bioinformatics analysis of Gene ontology (GO) enrichment, Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment, Protein-protein interaction (PPI) and subcellular localization prediction of DAPs showed that many DAPs were involved in protein structure, metabolic enzymes, protein turnover and so on. The correlation analyses indicated that 14 DAPs were significantly related with the fillet quality traits. Besides, several discovered proteins might be potential protein markers for pH, color, cooking loss and centrifuge loss of thawed largemouth bass fillet quality. These results provided a further understanding of quality stability of largemouth bass fillet treated by MNPMT from the perspective of proteomics.

A Study on the Development of Microwave Thawing Machine for Frozen Food Distrbution

A Study on the Development of Microwave Thawing Machine for Frozen Food Distrbution

Changes in myofibrillar protein gel quality of porcine longissimus muscle induced by its stuctural modification under different thawing methods

The effects of thawing methods (refrigeration thawing (RT, 4 °C), water immersion thawing (WT, 18 °C), vacuum thawing (VT, 25 °C), ultrasonic thawing (UT, 20 °C) and microwave thawing (MT)) on the conformation and gel qualities of myofibrillar protein (MP) obtained from porcine longissimus muscle were investigated. The results showed that MP conformation and gel qualities of porcine longissimus muscles by VT and UT were insignificantly changed compared to fresh meat (FM). A significant decrease in free amino groups of MP from MT illustrated that MT induced protein aggregation and oxidation (P < 0.05). The results of circular dichroism (CD) spectra analysis and fluorescence spectroscopy indirectly proved that thawing can cause protein cross-linking and degradation, secondary structure destruction, non-hydrophilic domain exposed and conformational change of samples. The largest changes in solubility, surface hydrophobicity and particle size were obtained with MT. The effects on the conformation and gel quality of MP were verified during thawing process.

Long-Term Stability Comparison between an Original and a Generic Version of Piperacillin/Tazobactam in Dextrose 5 % Infusion Polyolefin Bags at 5 ± 3 °C after Microwave Freeze-Thaw Treatment

Abstract Background Piperacillin-Tazobactam is frequently infused in hospitals. The use of a generic version was considered after the out of stock of the brand name Tazocin®. The stability of 4 g of Tazocin® in 120 mL of dextrose 5 % (D5) was demonstrated during 35 days at 5 °C ± 3 °C after freezing (−20 °C) and microwave thawing (FMT). The aim of the study was to investigate and compare the long-term stability of Tazocin® and a generic product in the same conditions. Methods Five polyolefin bags of 4 g of Piperacillin/Tazobactam® Sandoz and 5 bags of 4 g of Tazocin® were prepared under aseptic conditions in 120 mL of D5 and stored 3 months at 20 °C then thawed and stored 58 days at 5 ± 3 °C. Spectrophotometric absorbance at different wavelengths, pH measurement, visual and microscopic observations were also performed. The concentrations were measured by HPLC, at 211 nm for tazobactam and 230 nm for piperacilline. Results No significant change in pH values or optic densities, no crystals were detected. The lower confidence limit at 95 % of the concentration for the solutions remains superior to 90 % of the initial concentration until 58 days of storage at 5 ± 3 °C. Conclusion Under these conditions, 4 g/120 mL of Piperacillin/Tazobactam® Sandoz or Tazocin® in D5 infusion in polyolefin bags remains stable at least for 58 days at 5 ± 3 °C after FMT

Effect of magnetic nanoparticles plus microwave or far-infrared thawing on protein conformation changes and moisture migration of red seabream (Pagrus Major) fillets

In order to evaluate the effects of magnetic nanoparticles plus microwave (MNPMT) or far-infrared (MNPFT) thawing on protein conformation changes and moisture migration of red seabream (Pagrus major) fillets, cold storage thawing, microwave thawing, MNPMT, far-infrared thawing and MNPFT were subjected to red seabream fillets. DSC and dynamic rheology were conducted to analyze physicochemical changes. Raman spectra before and after isotope H/D exchange, intrinsic fluorescence and UV second derivative spectra were carried out to explore myofibrillar protein structural changes. Low-field NMR was used to test water migration. SEM was performed to observe fiber microstructure. Results indicated that MNPMT and MNPFT both had a desirable thermal stability and gelation property. Besides, both showed stable protein secondary and tertiary structure. Immobilized water in them also had no significant changes compared with fresh sample. This research provided some novel thawing technologies for application in food industry.

Ultrasound or microwave vacuum thawing of red seabream (Pagrus major) fillets

Ultrasound assisted vacuum thawing (UVT) or microwave vacuum thawing (MVT) with red seabream fillets were compared to fresh, chill storage thawing, vacuum thawing, microwave thawing and ultrasound thawing. The thermal stability and gelation properties were studied with DSC and dynamic rheology, respectively. Raman spectra before and after H/D isotope exchange and intrinsic fluorescence were used to measure protein secondary and tertiary structure. Low-field NMR was done to measure water migration. The two thawing techniques both retained actin thermal stability and generally retained more stable tertiary structures than the other thawing methods. MVT showed a desirable viscoelasticity of muscle proteins and UVT had a relatively stable secondary structure. There were no significant changes in free water. Thus, UVT and MVT could be used to improve the physicochemical properties of proteins during thawing of fillets.

Evaluation of the effects of different freezing and thawing methods on the quality preservation of Pleurotus eryngii

The individually quick-frozen (IQF) method is used to produce high-quality frozen food by freezing an individual piece of food separately from the remaining food. In this study, the effect of various freezing and thawing combinations on the quality preservation of Pleurotus eryngii (king oyster mushroom) was investigated. For this purpose, diced and mini P. eryngii mushrooms were frozen by natural freezing (NF, − 20 °C) or IQF (− 62.5 °C and speed 8.23 m/s) methods and thawed using three thawing methods—flowing water thawing (FT, 4 °C), microwave thawing (MT, 620 W), or natural air convection thawing (NT, 20 ± 5 °C). Quality characteristics, such as thawing loss, texture, water holding capacity, color, microstructure, and sensory quality, were evaluated. MT showed the most rapid thawing time, followed by FT and NT for all the samples. The results showed that thawing curve, water holding capacity, and hardness of IQF samples were better than those of NF samples after NT, FT, and MT. Scanning electron microscopy analysis revealed that cell integrity of the IQF sample was better than that of the NF sample. MT is the fastest of the thawing methods, but thawing after NF yielded a sample closest to the fresh mushroom sample. Therefore, when combined with NT, IQF minimized the quality changes in frozen diced and mini P. eryngii mushrooms. This study showed that the IQF technology can be used as a new preservation and distribution method of mushroom.

Effect of thawing conditions and corresponding frying temperature profiles on the formation of acrylamide in French fries

This study attempted to determine the effects of thawing conditions and corresponding frying temperature profiles on the formation of acrylamide in French fries. Frozen par-fried potato strips were thawed under three different conditions, at room temperature, using a chiller, and using a microwave. Unthawed par-fried potato strips were used as the control samples. Thawed (or unthawed) par-fried potato strips were deep-fat fried in palm oil at 180 ± 5 °C for 3.5 min. The temperature drop was monitored every 15 s for a total of 6 min; 3.5 min of frying time plus an additional 2.5 min until the oil temperature returned to 180 °C. The acrylamide content, oil content and colour of the French fries were measured. The frying temperature dropped substantially (more than 30 °C) from the initial temperature in the first 45 s of frying for all thawing conditions. After 90 s of frying, the smallest temperature drops were observed for French fries thawed using a microwave (20%), and the largest temperature drop prior to recovery was seen with the control sample (24%). At the end of the frying period (after 210 s), French fries thawed using a microwave had reached the highest final temperature (154 °C), and the control sample had reached the lowest final temperature (145 °C). The acrylamide contents of the French fries were found to be in the range of 77.4–106 ng/g, whereas the oil contents ranged from 16.4 to 20.5%. The lowest lightness, highest redness and highest yellowness were found for French fries thawed using a microwave. Although the thawing conditions did not significantly affect the formation of acrylamide, microwave thawing was found to be the best thawing method due to the resulting (relatively) low acrylamide and oil contents of the French fries and their desirable colour attributes. The results of this study can be used to recommend that the manufacturers of frozen par-fried potato strips specify the use of a microwave for thawing as part of the frying instruction on the packaging.

Effect of freezing and different thawing methods on the content of polyphenolic compounds of red grape skins

Due to the short period of the grape fresh samples availability and their very complex analysis, appropriate grape samples storage is mandatory. In this study, samples were analyzed immediately after harvest and after storage at −20 °C. Frozen samples were thawed as follows: at the room temperature, in the microwave oven, in the refrigerator, and the skin was pulled off from the frozen grape berries. The freezing had a positive effect on the contents of anthocyanins and flavonol glycosides. These compounds are contained in cell vacuoles thus membrane degradation, throughout the freezing process, could enhance their extractability. The freezing had a negative effect on the content of the other polyphenols which can be bound to the cell wall. Among examined thawing methods, the most appropriate method was the peeling grape berry skin from the frozen berries samples with the receptacle. Suitable alternative to the aforementioned method could be the microwave thawing. Practical application One of the most important groups of compounds contained in grape berries are polyphenolic compounds. These compounds significantly affect the quality of grapes and wine. They also have a positive impact on human health. Most of the grapes are being processed into wine, but it also has many other uses. Besides the table grapes, raisins, juices, jams, and wine distillates, currently, various cosmetic and pharmaceutical preparations made from grapes whose functioning is based on the effects of polyphenols are encounter on the market. Given the short period of availability of fresh grape samples and complex procedure of their analysis and processing, samples must be stored in an appropriate manner. This study reported the effect of freezing and applied thawing method on retentions of polyphenolics in grapes. The information obtained by this study is essential for the development of specific applications of the grape berries skins.

Introduction of alkali soaking and microwave drying processes to improve agar quality of Gracilaria verrucosa

Gracilaria species produce agars with low quality due to their high sulfate concentrations. For this reason, the gel properties of many Gracilaria agars must be improved by appropriate processes. In this study, we developed an improved agar extraction process for Gracilaria verrucosa by alkali soaking extraction and microwave thawing and drying. Variables such as the seaweed to alkali volume ratio, extraction time, and alkali concentration were adjusted to optimize the yield and agar quality. The yield of the agar was maximized (34.5±0.6%) using 3% alkali concentration; the lowest yield (17.0±1.7%) was obtained with 1% alkali concentration. Agar gel strengths ranged from 462.0±7 to 627.3±11 g·cm−2. We have developed a process for quickly producing an agar gel through thawing and drying using microwave radiation. This study shows the possibility of producing a high-value agar using alkali soaking extraction methods for nonedible G. verrucosa.

Effect of Freezing Rate and Microwave Thawing on Texture and Microstructural Properties of Potato (Solanum tuberosum).

Food freezing is a preservation process that works by lowering temperature while simultaneously decreasing water activity. It is accepted that although freezing preserves foods, it generally has a negative effect on textural quality. This research investigated the texture response of potatoes (Solanum tuberosum) as a function of time to freeze (defined as the time for the center temperature to reach -20 °C) and thawing process. Potatoes slices (6 mm) were blanched then frozen in an ethanol/carbon dioxide bath, a pilot scale high velocity air freezer (HVAF) and a still air freezer to achieve various times to freeze. Slices were stabilized at -20 °C and thawed by 2 methods; room temperature air and microwave. Afterwards, samples were allowed to come to room temperature prior to texture profile analysis (TPA). Results indicate a maximum texture loss of the potato was reached at a time to freeze of approximately 8 min (corresponding to the HVAF). The texture difference between room temperature and microwave thawing methods was not shown to be significant (P = 0.05). SEM images showed the cellular structure of the potato in a HVAF to be similar to that of the still air freezer, validating that the matrix was maximally damaged in both conditions. This work created a continuous quality loss model for the potato as a function of time to freeze and showed no textural benefit to high velocity over still air freezing.

Heterocyclic aromatic amines content in chicken burgers and chicken nuggets sold in fast food restaurants and effects of green tea extract and microwave thawing on their formation

The aims of the study were to investigate the presence of heterocyclic aromatic amines (HCAs) in chicken burgers (CBs) and chicken nuggets (CNs) purchased from fast food restaurants and the effects of green tea extract addition (GTE) into the covering material as well as microwave thawing (MT) on HCAs formation in CBs and CNs. Analysis of HCAs (IQx, IQ, MeIQx, MeIQ, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, AαC, and MeAαC) were performed using HPLC-DAD following solid phase extraction. While the total HCAs content varied between not quantified—9.72 ng/g meat and 1.94–22.01 ng/g meat for commercial CBs and CNs, it ranged between not quantified—3.42 ng/g meat and not quantified—0.31 ng/g meat for CBs and CNs produced in the laboratory, respectively. Commercial CBs and CNs contained high amounts of HCAs, with MeIQx being the dominant HCA in all analyzed samples however, GTE and MT did not reduce the HCAs formation in CBs and CNs. Practical applications Widely consumed fast food chicken products; chicken burgers and chicken nuggets contain high amounts of HCAs. That much HCA concentration in chicken burgers and chicken nuggets can endanger the public health seriously.

Dielectric properties of Antarctic krill (Euphausia superba) and white shrimp (Penaeus vannamei) during microwave thawing and heating

ABSTRACTDielectric properties of Antarctic krill and white shrimp were measured across the microwave frequency range 300–3000 MHz in a temperature range of −20 to 20 °C. To shorten thawing time, the effects of salt, sucrose and moisture contents on dielectric properties at 915 and 2450 MHz were also studied during microwave thawing (MT) and microwave heating (MH). The results indicate that the change in sucrose content had a smaller effect on dielectric properties, and only addition of salt had a significant influence (p < 0.05) on dielectric properties during MT. Moreover, when these shrimps with addition of a salt–sucrose mixture at 3% w/w were thawed and heated to 20 °C, the microwave processing time was no more than 130 s. Compared with the samples without any additives, thawing time shortened significantly when salt and sucrose were simultaneously added to the samples. Besides, the centre temperature and temperature distribution within the cross section of shrimps confirmed effects of various additives on dielectric properties, suggesting that MT and MH can be applied to the processing of freshwater and oceanic shrimp, and that addition of only salt or the salt–sucrose mixture can further quicken thawing and heating rates to optimize the industrial processing of shrimp.

Combined beef thawing using response surface methodology

Based on four thawing methods (still air, still water, ultrasonic wave, and microwave) and single-factor tests, we established a four-factor three-level response surface methodology for a regression model (four factors: pH, drip loss rate, cooking loss rate, protein content). The optimal combined thawing method for beef rib-eye is: microwave thawing (35 s work/10 s stop, totally 170 s) until beef surfaces soften, then air thawing at 15°C until the beef centre temperature reaches –8°C, and finally ultrasonic thawing at 220 W until the beef centre temperature rises to 0°C. With this method, the drip loss rate is 1.9003%, cooking loss rate is 33.3997%, and protein content is 229.603 μg, which are not significantly different from the model-predicted theoretical results (P ≥ 0.05).

Microwave thawing and green tea extract efficiency for the formation of acrylamide throughout the production process of chicken burgers and chicken nuggets.

Initially, we measured the acrylamide (AA) levels of chicken burgers (CBs) and chicken nuggets (CNs) purchased from fast food restaurants. After the determination of AA in these products, we aimed to investigate whether the use of green tea extract in the covering material, and microwave thawing before frying, mitigated the formation of AA in CBs and CNs during the production process. According to our study, AA concentrations of CBs and CNs purchased from fast food restaurants were in the range of 13.43-118.97 and 32.92-134.90 ng g-1 coating, respectively. In our experiment, AA levels varied between 19.61 and 40.08 ng g-1 coating for CBs and 7.92-49.60 ng g-1 coating for CNs. Green tea extract reduced the AA formation in CBs and CNs at the pan frying and steam oven cooking heat treatment steps (P < 0.05). However, microwave thawing did not affect AA level of CBs and CNs. When the AA levels of commercial CBs and CNs are compared with those produced in our experiment, the use of green tea extract could be a novel, easy and practical application for fast food producers to minimise AA levels in the first two steps of the production without changes to the sensory properties of the final products. © 2016 Society of Chemical Industry.

An investigation of the dielectric and thermal properties of frozen foods over a temperature from –18 to 80°C

ABSTRACTThe dielectric properties (dielectric constant [ε′] and dielectric loss factor [ε″]) for three frozen meals (basil fried chicken, green curry with chicken, and congee with minced pork) were measured at frequency 2.45 GHz from –18 to 80°C. Thermal properties (thermal conductivity [k] and specific heat capacity [c]) of each food item were characterized using their composition for improving the modeling of microwave thawing process of frozen products. For all frozen meals, similar trends in the dielectric and thermal properties values were observed as a function of temperature. In all samples of frozen foods, the dielectric properties (ε′, ε″) rapidly increased with temperature for the range from –10 to 0°C. Thereafter, dielectric properties linearly increased with temperature for basil fried chicken and congee with minced pork but linearly decreased with temperature for green curry with chicken from 0 to 80°C. The dielectric properties data bases were used to calculate power reflected (Pr), power transmitted (Pt), dielectric loss tangent (tanδ), and penetration depth (dp). These parameters were related to the dielectric properties. The thermal conductivity values of all samples decreased with increasing temperature in the frozen stage and little changed after thawing. While the specific heat capacity values increased first and then do not change considerably. The temperature-dependent material properties can give insight into how the food product interacts with the incident electromagnetic radiation.

The Effect of Pre-fermentative Freezing Treatment on the Sensory Quality of ‘Meili’ Rosé Wine

In this study, the effect of a pre-fermentative freezing treatment on quality attributes of ‘Meili’ rose wine was assessed. Prior to fermentation, ‘Meili’ grapes (berries and must) were subjected to a freezing treatment considering factors of freezing temperatures, freezing time, and thawing method. Colour-related indices were measured by spectral methods. Wine aroma characteristics and sensory attributes were assessed by trained panellists. The results revealed that lower freezing temperature and longer freezing time had positive effects on wine quality attributes. The treatment of frozen berries might help extract colour-related compounds. Microwave thawing improved wine colour, but decreased taste quality. In the work, the MF-10°C/6 h treatment (microwave-thawed berries that had been frozen at -10°C for 6 h) contributed to the best colour characteristics, whereas the NP-20°C/4 h treatment (naturally-thawed must that had been frozen at -20°C for 4 h) contributed to the best taste attributes.

ANN modeling for optimum storage condition based on viscoelastic characteristics and sensory evaluation of frozen cooked rice

The optimum frozen condition of cooked rice has been predicted by artificial neural network (ANN) based on the data obtained from sensory evaluations as well as viscoelastic measurements. Cooked rice was frozen and stored at −5, −15, and −45 °C for 0, 10, 30, 60 and 90 days. Then, after the samples were thawed by natural convection air at room temperature or microwave heating, the viscoelastic parameters were measured with the Tensipresser and sensory scores were evaluated by a 7-point scale. The sensory scores were predicted with high accuracy from the viscoelastic parameters by ANN models. In addition, the ANN model analysis using the dataset of storage conditions and palatability scores showed that to achieve palatability score greater than the central value of 4.0 after 40 days, storage temperature must be below −25 °C if air thawing by natural convection is used and below −15 °C if microwave thawing and heating are used.