Water dynamics of turbot flesh during frying, boiling, and stewing processes and its relationship with color and texture properties: Low-field NMR and MRI studies

Current State of Milk, Dairy Products, Meat and Meat Products, Eggs, Fish and Fishery Products Authentication and Chemometrics

Food fraud is a matter of major concern as many foods and beverages do not follow their labelling. Because of economic interests, as well as consumers' health protection, the related topics, food adulteration, counterfeiting, substitution and inaccurate labelling, have become top issues and priorities in food safety and quality. In addition, globalized and complex food supply chains have increased rapidly and contribute to a growing problem affecting local, regional and global food systems. Animal origin food products such as milk, dairy products, meat and meat products, eggs and fish and fishery products are included in the most commonly adulterated food items. In order to prevent unfair competition and protect the rights of consumers, it is vital to detect any kind of adulteration to them. Geographical origin, production methods and farming systems, species identification, processing treatments and the detection of adulterants are among the important authenticity problems for these foods. The existence of accurate and automated analytical techniques in combination with available chemometric tools provides reliable information about adulteration and fraud. Therefore, the purpose of this review is to present the advances made through recent studies in terms of the analytical techniques and chemometric approaches that have been developed to address the authenticity issues in animal origin food products.

pH-shift strategy improving the thermal stability and oxidation stability of rice starch/casein-based high internal phase emulsions for the application in fish cake

The thermal stability of the different pH-shift rice starch/casein-based high internal phase emulsions (SC-HIPE) were evaluated in the present study to verify potential in improving the quality of fish cake. The results showed that the pH-shift treatment improved thermal stability (from 27.23% to 76.33%) and oxidation time (from 5.01 h to 6.86 h) of SC-HIPE, which showed the smaller droplet size (decreased from 15.14 to 1.64 μm) and higher storage module. The breaking force of FC with thermal stable SC-HIPE (average 64.95 g) was higher than that with thermal unstable SC-HIPE (51.05 g). The cohesiveness, adhesiveness and chewiness could be improved by adding thermal stable SC-HIPE, compared with pork fat. Additionally, combining sensory evaluation, the thermal stable SC-HIPE improved the gel quality, thus it could be completely replaced pork fat in the preparation of FC, which provided theoretical guidance for the preparation and application of fat substitutes.

Effect of water-retention agents on Scomberomorus niphonius surimi after repeated freeze–thaw cycles: low-field NMR and MRI studies

Repeated freeze–thaw cycles can directly cause the changes in the water distribution, physicochemical characteristics, and microstructure of Scomberomorus niphonius surimi. To improve the quality of S. niphonius surimi, the effect of water retention agents (phosphate and trehalose) was investigated during freeze-thaw cycles. The results of low-field nuclear magnetic resonance (LF-NMR) combined with magnetic resonance imaging (MRI) analysis showed that the water retention agents could obviously decrease the water loss and water mobility during repeated freeze–thaw cycles. Water retention agent significantly reduced the cook loss and improved the surimi quality by decreasing the surimi protein denaturation. The scanning electron microscopy (SEM) characterization revealed that water retention agents could obviously ameliorate the protein structure damage. In addition, the principal component analysis combined with LF-NMR parameters showed clear discrimination between samples supplemented with different water retention agents. In a word, the LF-NMR and MRI might provide useful information in a non-invasive manner for monitoring the effects of water-retention agents on surimi after repeated freeze–thaw cycles.

Effect of Different Processing Methods on Quality, Structure, Oxidative Properties and Water Distribution Properties of Fish Meat-Based Snacks

Snack foods are consumed around to globe due to their high nutrition, taste and versatility; however, the effects of various processing methods on quality, structure and oxidative properties are scare in the literature. This study aims to evaluate the effect of various processing methods (frying, baking and microwave cooking) on quality, structure, pasting, water distribution and protein oxidative properties of fish meat-based snacks. The results showed that the frying method induced a significantly (p < 0.05) higher expansion than baking and microwave methods. Texture in terms of hardness was attributed to the rapid loss of water from muscle fiber, which resulted in compact structure and the increased hardness in microwave cooking, whereas in frying, due to excessive expansion, the hardness decreased. The pasting properties were significantly higher in baking, indicating the sufficient swelling of starch granules, while low in microwave suggest the rapid heating, which degraded the starch molecules and disruption of hydrogen bonds as well as glycosidic linkage and weakening of granules integrity. The water movement assessed by Low Field Nuclear Magnetic Resonance (LF-NMR) showed that frying had less tight and immobilized water, whereas microwave and baking had high amounts of tight and immobilized water, attributing to the proper starch-protein interaction within matrix, which was also evidenced by scanning electron microscopy (SEM) analysis. The protein oxidation was significantly (p < 0.05) higher in frying compared to baking and microwave cooking. The findings suggest the endorsement of baking and microwave cooking for a quality, safe and healthy snacks.

Effect of pre-frying on distribution of protons and physicochemical qualities of mackerel

BACKGROUND

In this work, low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging were used to investigate the changes in protons (from water and oil) distribution of mackerel during the frying process. The relationship between proton migration and some physicochemical indexes was established by partial least squares regression (PLSR). The changing mechanism of the quality characteristics and physicochemical properties of fish meat under different frying conditions was analysed by LF-NMR combined with PLSR, which provided theoretical support for the development of canned mackerel food.

RESULTS

LF-NMR results showed that three kinds of T₂ protons assigned to protein-water interaction (T₂₁ ), multilayer bound water (T₂₂ ), oil and free water (T₂₃ ), respectively. As the frying temperature increased, protons from the T₂₂ peak significantly decreased, while protons from the T₂₃ peak remarkably increased. The microstructure of fried mackerel was destroyed; cooking loss, oil content, a* value, b* value, hardness and chewiness increased; and the protein content and L* value decreased. Furthermore, PLSR analysis revealed that significant correlation was observed between the cooking loss, TPA parameter (chewiness), colour parameter (L*) and LF-NMR parameters.

CONCLUSION

Different frying temperatures and times had a strong effect on the physicochemical properties of mackerel. Good prediction models could be established by proton migration using the LF-NMR technique and PLSR for fried mackerel. Quality control of fried fish could be realized by monitoring the change in LF-NMR data. © 2021 Society of Chemical Industry.

The Hydration Characteristics, Structural Properties and Volatile Profile of Squid (Symplectoteuthis oualaniensis) Mantle Muscle: Impacts of Steaming, Boiling, and Sous Vide Cooking

Herein, the effects of boiling (BO), steaming (ST), and sous vide (SV) on the hydration characteristics, structural properties, and volatile profile of squid (Symplectoteuthis oualaniensis) mantle muscle (SMM) were investigated. Three cooking methods resulted in a dramatic decrease in proton mobility and freedom of protons, the relaxation time T₂ decreased after cooking, and the water binding in the SMM was closer, but the SV treatment could retain more water in the SMM. SV resulted in a lower cooking loss (10.8%) than ST (49.0%) and BO (36.7%). Samples treated with SV had a better color and texture, the secondary structure β-fold of the squid protein was damaged by cooking to a certain extent, and the damage degree was BO > ST > SV. Compared with BO and ST, SV treatment caused more damage to the myosin heavy chain, paramyosin, and actin in SMM, improved the tenderness of SMM, and resulted in more regular internal reticular structures and less formation of fibrous structures. Cooking methods can significantly affect the volatile components of SMM, resulting in increasing volatile components or generating new volatile components in SMM including 2-methylbutanal, ethyl 2-methylpropanoate, acetic acid, and propyl methyl ketone in ST and BO samples and 2-methylbutanal, hexanal, and 2,3-pentanedione in SV samples. Therefore, SV resulted in the best quality squids and has substantial industrial application potential.

Monitoring Thermal and Non-Thermal Treatments during Processing of Muscle Foods: A Comprehensive Review of Recent Technological Advances

Muscle food products play a vital role in human nutrition due to their sensory quality and high nutritional value. One well-known challenge of such products is the high perishability and limited shelf life unless suitable preservation or processing techniques are applied. Thermal processing is one of the well-established treatments that has been most commonly used in order to prepare food and ensure its safety. However, the application of inappropriate or severe thermal treatments may lead to undesirable changes in the sensory and nutritional quality of heat-processed products, and especially so for foods that are sensitive to thermal treatments, such as fish and meat and their products. In recent years, novel thermal treatments (e.g., ohmic heating, microwave) and non-thermal processing (e.g., high pressure, cold plasma) have emerged and proved to cause less damage to the quality of treated products than do conventional techniques. Several traditional assessment approaches have been extensively applied in order to evaluate and monitor changes in quality resulting from the use of thermal and non-thermal processing methods. Recent advances, nonetheless, have shown tremendous potential of various emerging analytical methods. Among these, spectroscopic techniques have received considerable attention due to many favorable features compared to conventional analysis methods. This review paper will provide an updated overview of both processing (thermal and non-thermal) and analytical techniques (traditional methods and spectroscopic ones). The opportunities and limitations will be discussed and possible directions for future research studies and applications will be suggested.

Spectroscopic Techniques for Monitoring Thermal Treatments in Fish and Other Seafood: A Review of Recent Developments and Applications

Cooking is an important processing method, that has been used since ancient times in order to both ensure microbiological safety and give desired organoleptic properties to the cooked food. Fish and other seafood products are highly sensitive to thermal treatments and the application of severe heat can result in negative consequences on sensory and nutritional parameters, as well as other quality attributes of the thermally processed products. To avoid such undesired effects and to extend the shelf life of these perishable products, both the heat processing methods and the assessment techniques used to monitor the process should be optimized. In this review paper, the most common cooking methods and some innovative ones will first be presented with a brief discussion of their impact on seafood quality. The main methods used for monitoring heat treatments will then be reviewed with a special focus on spectroscopic techniques, which are known to be rapid and non-destructive methods compared to traditional approaches. Finally, viewpoints of the current challenges will be discussed and possible directions for future applications and research will be suggested. The literature presented in this review clearly demonstrates the potential of spectroscopic techniques, coupled with chemometric tools, for online monitoring of heat-induced changes resulting from the application of thermal treatments of seafood. The use of fluorescence hyperspectral imaging is especially promising, as the technique combines the merits of both fluorescence spectroscopy (high sensitivity and selectivity) and hyperspectral imaging (spatial dimension). With further research and investigation, the few current limitations of monitoring thermal treatments by spectroscopy can be addressed, thus enabling the use of spectroscopic techniques as a routine tool in the seafood industry.

Use of Spectroscopic Techniques for a Rapid and Non-Destructive Monitoring of Thermal Treatments and Storage Time of Sous-Vide Cooked Cod Fillets

In this work, the potential of spectroscopic techniques was studied to investigate heat-induced changes occurring during the application of thermal treatments on cod (Gadus morhua L.) fillets. Vacuum-packed samples were thermally treated in a water bath at 50, 60, 70 and 80 °C for 5 and 10 min, and further stored for one, four, and eight days at 4 ± 1 °C before analysis. Several traditional (including cooking loss, drip loss, texture, protein solubility, protein oxidation, and color) and spectroscopic (fluorescence and diffuse reflectance hyperspectral imaging) measurements were conducted on the same samples. The results showed a decrease in fluorescence intensity with increasing cooking temperature and storage time, while the impact of cooking time was only noticeable at low temperatures. Diffuse reflectance data exhibited a decrease in absorbance, possibly as a result of protein denaturation and increased scattering at higher cooking temperatures. Both fluorescence and diffuse reflectance data were highly correlated with color parameters, whereas moderate correlations were observed with most other traditional parameters. Support vector machine models performed better than partial least square ones for both classification of cod samples cooked at different temperatures and in prediction of the cooking temperature. The best classification result was obtained on fluorescence data, achieving an accuracy of 92.5%, while the prediction models resulted in a root mean square error of prediction of cooking temperature lower than 5 °C. Overall, the classification and prediction models showed good results, indicating that spectroscopic techniques, especially fluorescence hyperspectral imaging, have a high potential for monitoring thermal treatments in cod fillets.

Effect of Different Cooking Methods on Proton Dynamics and Physicochemical Attributes in Spanish Mackerel Assessed by Low-Field NMR

The states of protons within food items are highly related to their physical attributes. In this study, the effect of cooking methods including boiling, steaming, roasting and frying on proton dynamics, physicochemical parameters and microstructure of Spanish mackerel was assessed by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. The treatment of cooking resulted in a significant reduction of proton mobility and declined freedom of protons. The state changes of protons can be monitored easily in an intuitive and non-destructive manner during various cooking process. The treatments of boiling, steaming, roasting and frying resulted in different cooking loss and similar water-holding capability. A significant increase of total carbonyl content and thiobarbituric acid reactive substances was found, while a decrease of the values for free thiols and surface hydrophobicity was observed. The analysis of circular dichroism spectroscopy and cryo-scanning electron microscopy showed significant structural change. The correlation coefficients of R_cal² and R_cv² from partial least squares (PLS) regression models were more than 0.980, suggesting good correlation between LF-NMR data and hardness, resilience, springiness, chewiness, gumminess, and adhesiveness. Good recoveries and a relatively small coefficient of variation (CV) were obtained from the PLS regression models, indicating good reliability and accuracy in predicting texture parameters for mackerel samples.

The impact of hydrophilic emulsifiers on the physico-chemical properties, microstructure, water distribution and in vitro digestibility of proteins in fried snacks based on fish meat

Hydrophillic emulsifiers strengthened the starch–protein interaction which resulted in improved physio-chemical properties of friend snacks based on fish meat.

Low-Field NMR and MRI to Analyze the Effect of Edible Coating Incorporated with MAP on Qualities of Half-Smooth Tongue Sole (Cynoglossus Semilaevis Günther) Fillets during Refrigerated Storage

Nondestructive and fast measurement and characterization of fish is highly desired during various processing treatments. This research investigated the effectiveness of low field LF-NMR and MRI as fast monitoring techniques to estimate the qualities of half-smooth tongue sole fillets treated with edible coating combined with modified atmosphere packaging during refrigeration. T2 relaxation spectra showed three peaks representing bound water (T21), immobile water (T22), and free water (T23), respectively. pT22 accounted for the largest proportion of three types of water, followed by pT23. The weighted MRI provided the internal structure information associated with different samples, indicting the combination of edible coating and MAP (70% CO2 + 30% N2) is the best performance in the maintenance of qualities and freshness of HTS fillets. All results demonstrated that the combination of LF-NMR and MRI as fast and nondestructive methods have great potential to monitor qualities deterioration and predict shelf life in of HTS fillets during refrigerated storage.