Rapid, accurate, and simultaneous measurement of water and oil contents in the fried starchy system using low-field NMR

Effect of electrohydrodynamic (EHD) drying on active ingredients, textural properties and moisture distribution of yam (Dioscorea opposita)

This paper systematically investigates the changes in material properties during electrohydrodynamic (EHD) drying, the discharge characteristics of the EHD system as well as the active ingredients, textural properties (hardness, adhesiveness, etc.) and moisture distribution of yam under EHD, air drying and hot air drying were investigated. The results showed that the active particles and the ionized wind generated during the discharge process of the electrohydrodynamic drying device had a significant effect on the drying. Compared to thermal drying, 21 kV drying resulted in the most complete cellular structure, the best internal bound water content as well as textural properties of yam. It played a positive role in the retention of internal nutrients in yam, and the total phenol and allantoin contents were increased by 25.74% and 81.99%, respectively. These results elucidate the advantages of electrohydrodynamic drying in yam drying and provide a reference for the application of EHD in drying.

Control of the oil content of fried dough sticks through modulating structure change by reconstituted gluten fractions

In our study, we explored how gluten's role during dough formation and thermal processing can mitigate the adverse effects of physical factors on product quality. We discovered that a gluten network with a gliadin/glutenin ratio of 5:5 effectively limits oil penetration into the dough's core. This particular ratio is found to reduce the exposure of hydrophobic groups due to the presence of hydrated β-sheet structures. In contrast, gluten networks with higher gliadin proportions than typical wheat gluten tend to be looser, leading to increased chromophore exposure and facilitating more oil absorption. These observations highlighted the complex link between changes in gluten structure, varying protein compositions, and oil content in fried dough sticks. This research provided a foundation for developing specialized low-fat wheat flour and improving the quality of fried dough products.

Quantitative characterization of the crosslinking degree of hydroxypropyl guar gum fracturing fluid by low-field NMR

As a widely used water-based fracturing fluid, the performance of hydroxypropyl guar gum fracturing fluid is closely related to the degree of crosslinking, the quantitative characterization of which can reveal a detailed crosslinking mechanism and guide the preparation of fracturing fluid gels with an excellent performance. However, the commonly used high-temperature rheology method for evaluating the performance of fracturing fluids only qualitatively reflects the degree of crosslinking. In this study, low-field nuclear magnetic resonance (LF-NMR) was used to characterize the degree of crosslinking in guar gum fracturing fluid gels. The spin-spin relaxation time of the H proton in guar gum was molecularly analyzed using LF-NMR. The viscoelastic properties met the requirements when the crosslinking degree of the gel was 88-94 %. The transformation of the linear structure into a membrane structure during the crosslinking process of the guar gum fracturing fluid was confirmed by freeze-drying and scanning electron microscopy (SEM) from a microscopic perspective. The changing trend of the microstructure and viscoelastic properties of the fracturing fluid gel under different crosslinker dosages was consistent with changes in the degree of crosslinking. The LF-NMR test process is non-destructive to the gel structure, and the test results demonstrate good accuracy and repeatability.

Wheat gluten structure and (non-)covalent network formation during deep-fat frying

The aim of this work was to investigate wheat gluten protein network structure throughout the deep-frying process and evaluate its contribution to frying-induced micro- and macrostructure development. Gluten polymerization, gluten-water interactions, and molecular mobility were assessed as a function of the deep-frying time (0 - 180 s) for gluten-water model systems of differing hydration levels (40 - 60 % moisture content). Results showed that gluten protein extractability decreased considerably upon deep frying (5 s) mainly due to glutenin polymerization by disulfide covalent cross-linking. Stronger gliadin and glutenin protein-protein interactions were attributed to the formation of covalent linkages and evaporation of water interacting with protein chains. Longer deep-frying (> 60 s) resulted in progressively lower protein extractabilities, mainly due to the loss in gliadin protein extractability, which was associated with gliadin co-polymerization with glutenin by thiol-disulfide exchange reactions. The mobility of gluten polymers was substantially reduced during deep-frying (based on the lower T2 relaxation time of the proton fraction representing the non-exchanging protons of gluten) and gluten proteins gradually transitioned from the rubbery to the glassy state (based on the increased area of said protons). The sample volume during deep-frying was strongly correlated to the reduced protein extractability (r = -0.792, p < 0.001) and T2 relaxation time of non-exchanging protons of gluten proteins (r = -0.866, p < 0.001) thus demonstrating that the extent of gluten structural expansion as a result of deep-frying is dictated both by the polymerization of proteins and the reduction in their molecular mobility.

Construction and Properties of Oil-Loaded Soybean Protein Isolate/Polysaccharide-Based Meat Analog Fibers

Rationally designing the fibrous structure of artificial meat is a challenge in enriching the organoleptic quality of meat analogs. High-quality meat analog fibers have been obtained by wet-spinning technique in our previous study, whereas introducing oil droplets will further achieve their fine design from the insight of microstructure. Herein, in this current work, oil was introduced to the soybean protein isolate/polysaccharide-based meat analog fibers by regulating the oil droplets' size and content, which, importantly, controlled the spinning solution characterization as well as structure-related properties of the meat analog fiber. Results showed that the oil dispersed in the matrix as small droplets with regular shapes, which grew in size as the oil content increased. Considering the effect of oil droplets' size and content on the spinnability of the spinning solution, the mechanical stirring treatment was chosen as the suitable treatment method. Importantly, increasing the oil content has the potential to enhance the juiciness of meat analog fibers through improvements in water-holding capacity and alterations in water mobility. Overall, the successful preparation of oil-loaded plant-based fiber not only mimicked animal muscle fiber more realistically but also provided a general platform for adding fat-soluble nutrients and flavor substances.

An easy-built Halbach magnet for LF-NMR with high homogeneity using optimized target-field passive shimming method

The aim of this work is to develop a Halbach magnet that possesses characteristics such as easy-built, low cost and high homogeneity for use in a portable low-field NMR (LF-NMR) system. Considering portability, a 4-ring Halbach magnet was designed through simulation and mechanical modelling, which was successfully constructed in a general laboratory setting. The obtained field strength (B0) was 0.169 T, with an initial homogeneity of 8204 ppm within a sphere with a diameter of 20 mm. To enhance robustness, efficiency and effectiveness of shimming, an optimized target-field passive shimming method was proposed. Subsequently, the homemade spectrometer was used to run NMR experiments on the Halbach magnet. The 1H NMR linewidths of water samples became significantly narrower after passive shimming, e.g., the linewidth of a sample with a diameter of 3 mm and a length of 3 mm reduced from 452.3 Hz (62.5 ppm) to 12.9 Hz (1.8 ppm), which was much less than 102 Hz. The NMR results demonstrate that the proposed passive shimming method can achieve high homogeneity, and the developed Halbach magnet is capable of satisfying numerous LF-NMR applications.

Perspectives on Novel Technologies of Processing and Monitoring the Safety and Quality of Prepared Food Products

With the changes of lifestyles and rapid growth of prepared food industry, prepared fried rice that meets the consumption patterns of contemporary young people has become popular in China. Although prepared fried rice is convenient and nutritious, it has the following concerns in the supply chain: (1) susceptible to contamination by microorganisms; (2) rich in starch and prone to stall; and (3) vegetables in the ingredients have the issues of water loss and discoloration, and meat substances are vulnerable to oxidation and deterioration. As different ingredients are used in prepared fried rice, their food processing and quality monitoring techniques are also different. This paper reviews the key factors that cause changes in the quality of prepared fried rice, and the advantages and limitations of technologies in the processing and monitoring processes. The processing technologies for prepared fried rice include irradiation, high-voltage electric field, microwave, radio frequency, and ohmic heating, while the quality monitoring technologies include Raman spectral imaging, near-infrared spectral imaging, and low-field nuclear magnetic resonance technology. These technologies will serve as the foundation for enhancing the quality and safety of prepared fried rice and are essential to the further development of prepared fried rice in the emerging market.

Exploring the influence mechanism of water grinding on the gel properties of corn starch based on changes in its structure and properties

BACKGROUND

At present, most studies have focused on the preparation of modified starches by dry grinding. As an excellent starch plasticizer, water might enhance the action of grinding on the structure of starch granules, and water grinding might improve the gel properties of starch. Therefore, this article explored the influence mechanism of water grinding on the gel properties of corn starch based on the changes in its structure and properties.

RESULTS

The results showed that water grinding could make water enter the starch granules and hydrate the starch molecules, and the starch gelatinized after water grinding for 20 min. Thus, water enhanced the action of grinding on the structure of the starch granules. Under the plasticization and grinding action of water grinding, the mechanochemical effect of the starch granules occurred. When the starch was in the aggregation stage (7.5-10 min), the crystallinity of the starch increased, and the starch molecules rearranged into a more stable structure, which increased apparent viscosity (η), elastic modulus (G') and viscous modulus (G″) of the starch gels.

CONCLUSION

Therefore, appropriate water grinding (10 min) contributed to increasing the viscoelasticity of starch gels. This study provided a theoretical foundation for research on improving the properties of starch by mechanical modification in future. © 2023 Society of Chemical Industry.

Enhanced freeze-thawing stability of water-in-oil pickering emulsions stabilized by ethylcellulose nanoparticles and oleogels

This study developed water-in-oil (W/O) Pickering emulsions stabilized by ethylcellulose (EC) nanoparticles and EC oleogels, which presented significantly improved freeze-thawing (F/T) stability. Microstructural observation suggested EC nanoparticles were distributed at the interface and within the water droplets, and the EC oleogel trapped oil in the continuous phase. Freezing and melting temperatures of water in the emulsions with more EC nanoparticles were lowered and the corresponding enthalpy values were reduced. F/T led to lower water binding capacity but higher oil binding capacity of the emulsions, compared to the initial emulsions. Low field-nuclear magnetic resonance confirmed the increased mobility of water but decreased mobility of oil in the emulsions after F/T. Both linear and nonlinear rheological properties proved that emulsions exhibited higher strength and higher viscosity after F/T. The widened area of the elastic and viscous Lissajous plots with more nanoparticles suggested the viscosity and elasticity of emulsions were increased.

The Effect of Different Ratios of Starch and Freeze-Thaw Treatment on the Properties of Konjac Glucomannan Gels

The composite gels of konjac glucomannan (KGM) and corn starch (CS) were prepared and treated by the freeze-thaw method. For KGM-CS gels, as the starch ratio rose from 0 to 100%, storage modulus (G') decreased by 97.7% (from 3875.69 Pa to 87.72 Pa), degradation temperature decreased from 313.32 °C to 293.95 °C, and crystallinity decreased by 16.7%. For F-KGM-CS gels, G' decreased by 99.0% (from 20,568.10 Pa to 204.09 Pa), degradation temperature increased from 289.68 °C to 298.07 °C, and crystallinity decreased by 17.1% with more starch content. The peak in infrared spectroscopy shifted to a higher wavenumber with more starch and to a lower wavenumber by freezing the corresponding composite gels. The detected retrogradation of the composite gels appeared for KGM-CS with 80% starch and F-KGM-CS with 40% starch. The endothermic enthalpy of free water rose by 10.6% and 10.1% with the increase in starch for KGM-CS and F-KGM-CS, respectively. The results of moisture distribution found that bound water migrated to free water and the water-binding capacity reduced with more starch. The results demonstrated that the molecular interaction in composite gels was weakened by starch and strengthened by freezing.

Continuous Monitoring of the Hydration Behavior of Hydrophilic Matrix Tablets Using Time-Domain NMR

Time-domain NMR (TD-NMR) was used for continuous monitoring of the hydration behavior of hydrophilic matrix tablets. The model matrix tablets comprised high molecular weight polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG). The model tablets were immersed in water. Their T₂ relaxation curves were acquired by TD-NMR with solid-echo sequence. A curve-fitting analysis was conducted on the acquired T₂ relaxation curves to identify the NMR signals corresponding to the nongelated core remaining in the samples. The amount of nongelated core was estimated from the NMR signal intensity. The estimated values were consistent with the experiment measurement values. Next, the model tablets immersed in water were monitored continuously using TD-NMR. The difference in hydration behaviors of the HPMC and PEO matrix tablets was then characterized fully. The nongelated core of the HPMC matrix tablets disappeared more slowly than that of the PEO matrix tablets. The behavior of HPMC was significantly affected by the PEG content in the tablets. It is suggested that the TD-NMR method has potential to be utilized to evaluate the gel layer properties, upon replacement of the immersion medium: purified (nondeuterated) water is replaced with heavy (deuterated) water. Finally, drug-containing matrix tablets were tested. Diltiazem hydrochloride (a highly water-soluble drug) was employed for this experiment. Reasonable in vitro drug dissolution profiles, which were in accordance with the results from TD-NMR experiments, were observed. We concluded that TD-NMR is a powerful tool to evaluate the hydration properties of hydrophilic matrix tablets.

Rapid and Simultaneous Measurement of Fat and Moisture Contents in Pork by Low-Field Nuclear Magnetic Resonance

In order to improve the efficiency of Soxhlet extraction and oven drying, low-field nuclear magnetic resonance (LF-NMR) technology was used to detect fat and moisture contents in pork. The transverse relaxation time (T2) distribution curves were constructed by Carr−Purcell−Meiboom−Gill (CPMG) experiments. In addition, the optimal conditions of adding MnCl2 aqueous solution was explored to separate water and fat signal peaks. Finally, the reliability of this method for the determination of fat and moisture contents in pork was verified. The present study showed that adding 1.5 mL of 20% MnCl2 aqueous solution solution at 50 °C can isolate and obtain a stable peak of fat. The lard and 0.85% MnCl2 aqueous solution were used as the standards for fat and moisture measurements, respectively, and calibration curves with R2 = 0.9999 were obtained. In addition, the repeatability and reproducibility of this method were 1.71~3.10%. There was a significant correlation (p < 0.05) between the LF-NMR method and the conventional methods (Soxhlet extraction and oven drying), and the R2 was 0.9987 and 0.9207 for fat and moisture, respectively. All the results proved that LF-NMR could determine fat and moisture contents in pork rapidly and simultaneously.

Enhanced Bioaccessibility of Microencapsulated Puerarin Delivered by Pickering Emulsions Stabilized with OSA-Modified Hydrolyzed Pueraria montana Starch: In Vitro Release, Storage Stability, and Physicochemical Properties

Puerarin is a bioactive flavonoid isolated from Kudzu roots that possesses numerous health benefits. However, its poor bioavailability and existing complex delivery systems with safety issues are challenging tasks for its incorporation into functional foods. Preparing modified-starch-stabilized Pickering emulsions containing microencapsulated puerarin with improved bioaccessibility was the key objective of the present research work. Acid-hydrolyzed high-amylose Pueraria montana starch (PMS) was modified with octenyl succinic anhydride (OSA) and evaluated as an emulsifier to prepare emulsions. The FTIR, SEM, and XRD results showed that PMS was successfully modified. Furthermore, the emulsification index (EI), mean droplet size, and ζ-potential values showed that modified starch with a higher degree of substitution (DS) enhanced the storage stability of emulsions. Similarly, the retention degree and encapsulation efficiency results of puerarin proved the assumption after storage of 16 d. The Pickering emulsions also helped in the controlled release of microencapsulated puerarin in vitro. The study outcomes proved that Pickering emulsions stabilized with OSA-modified PMS have promising applicability in functional foods as efficient food-grade delivery systems, enhancing oral supplementation and accessibility of puerarin.

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.

Radio frequency as an innovative method to produce low-fat French fries

BACKGROUND

A large amount of evidence shows that excessive fat intake can increase the risk of obesity, type 2 diabetes, non-alcoholic fatty liver disease, and cardiovascular disease. The main purpose of this study was to use radio frequency (RF) technology to prepare low-fat French fries.

RESULTS

RF treatment for 10 min significantly decreased the force required to cut potatoes and inhibited the enzymatic browning of fresh-cut potatoes. Moreover, RF treatment increased the hardness, gumminess, and chewiness of French fries from 388.55 g, 85.67, and 33.27 to 776.93 g, 159.36, and 70.11, respectively. Furthermore, RF treatment for 10 min reduced the oil content of French fries by 28.0% compared to that of the control group. This result was related to the pre-gelatinized potato starch content after RF treatment. Pre-gelatinized starch forms a 'protective film', that prevents oil from entering the fries during frying.

CONCLUSION

Moderate RF treatment (10 min) reduced the oil content of French fries without making their texture significantly different from that of commercial French fries. These findings may provide a new perspective for the application of RF technology in the development of low-fat fried foods. © 2022 Society of Chemical Industry.

Analysis of molecular mobility in corn and quinoa flours through 1H NMR and its relationship with water distribution, glass transition and enthalpy relaxation

Solids-water interactions of corn and quinoa flours were evaluated through ¹H NMR, DSC, and water sorption isotherms. Glass transition temperature (T_g), observed by DSC, was better distinguished through FID signals, and correlated to water content through the Gordon and Taylor model. Enthalpy relaxations, identified by thermal analysis at 50-70 °C were studied through transverse relaxation times (T₂) measured after Hahn spin-echo sequence, which revealed a rearrangement of the biopolymers structures that cause immobilization of polymer chains and reduced mobility of water molecules with weak interactions with solids (lower T₂₂). The higher lipid content of quinoa flour was manifested after the CPMG sequence (T₂ ≈ 100 ms) and caused reduced hygroscopicity and T_g values compared with corn flour systems. ¹H NMR resulted efficient for assigning proton populations and understanding the changes in their distribution with temperature, analyzing glass transition and interpreting the implications of enthalpy relaxations processes in corn and quinoa flours.

Characterization of the Salt and Free Base of Active Pharmaceutical Ingredients Based on NMR Relaxometry Measured by Time Domain NMR

NMR relaxometry measurement by time domain NMR (TD-NMR) is a promising technique for characterizing the properties of active pharmaceutical ingredients (APIs). This study is dedicated to identifying the salt and free base of APIs by NMR relaxometry measured by the TD-NMR technique. Procaine (PC) and tetracaine (TC) were selected as model APIs to be tested. By using conventional methods including powder X-ray diffraction and differential scanning calorimetry, this study first confirmed that the salt and free base of the tested APIs differ from each other in their crystalline form. Subsequently, measurements of T₁ and T₂ relaxation were performed on the tested APIs using TD-NMR. The results demonstrated that these NMR relaxometry measurements have sufficient capacity to distinguish the difference between the free base and salt of the tested APIs. Furthermore, quantification of the composition of the binary powder blends consisting of salt and free bases was conducted by analyzing the acquired T₁ and T₂ relaxation curves. The analysis of the T₁ relaxation curves provided a partly acceptable estimation: a good estimation of the composition was observed from PC powders, whereas for TC powders the estimation accuracy changed with the free base content in the binary blends. For the analysis on T₂ relaxation curves, a precise estimation of the composition was observed from all the samples. From these findings, the NMR relaxometry measurement by TD-NMR, in particular the T₂ relaxation measurement, is effective for evaluating the properties of APIs having different crystalline forms.

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.

Time-domain NMR analysis for the determination of water content in pharmaceutical ingredients and wet granules

The application of time-domain NMR (TD-NMR) analysis to quantify water content in pharmaceutical ingredients is demonstrated. The initial phase of the study employed a range of disintegrants with defined amounts of added water (0-30% of the total weight) as samples; the disintegrants included croscarmellose sodium, corn starch, low-substituted hydroxypropyl cellulose, and crospovidone. After acquisition of the T₂ relaxation curves of the samples by TD-NMR measurements, these curves were analyzed by partial least squares (PLS) regression. According to the analysis, accurate and reliable PLS models were created that enabled accurate assessment of water content in the samples. A powder blend consisting of acetaminophen (paracetamol) and tablet excipients was also examined. Both a physical mixture of the powder blend and a wet granule prepared with a high-speed granulator were tested as samples in this study. Precise determination of water content in the powder blend was achieved by using the TD-NMR method. The accuracy of water content determination was equivalent to or better than that of the conventional loss on drying method. TD-NMR analysis samples were measured nondestructively and rapidly with low cost; thus, it could be a powerful quantitative method for determining water content in pharmaceuticals.

Effect of annealing and heat-moisture pretreatments on the oil absorption of normal maize starch during frying

The impacts of two hydrothermal pretreatments, annealing (ANN) and heat moisture treatment (HMT), on oil-absorption by normal maize starch (NMS) during frying were investigated using low-field nuclear magnetic resonance (LF-NMR). The structural organizations of the fried samples were also evaluated using SEM, XRD, ATR-FTIR, and DSC, respectively. Both hydrothermal pretreatments significantly reduced the total oil content in the starch after frying, with the magnitude of the effect depending on the treatment conditions used. SEM showed that the pretreated fried starch granules preserved more of their original morphology. XRD, FTIR, and DSC showed that both pretreatments preserved more of the short-range double helices and long-range organizations within the orthorhombic crystalline structure for NMS during frying. The promoting effect of ANN/HMT on the interactions of starch molecules and the rearrangement of double helices were hypothesized to be responsible for the increased thermal stability of starch granules in the present work. As a result, fried starch pretreated by ANN/HMT were more organized and more compact than fried NMS, thus inhibiting oil absorption during frying.

Simultaneous, Rapid and Nondestructive Determination of Moisture, Fat Content and Storage Time in Leisure Dried Tofu Using LF-NMR

Leisure dried tofu is a kind of small packaged food which is popular with consumers in China. However, during the storage of leisure dried tofu, moisture and fat may be lost and deteriorate. For their own benefit, bad business operators might forge or mark the production date and shelf life. Therefore, it is necessary to explore a method to determine simultaneously the moisture, fat content, and storage time of leisure dried tofu. Samples were measured for obtaining transverse relaxation data by using low-field nuclear magnetic resonance (LF-NMR) spectrometer. The experimental data were analyzed and modeled by methods including partial least squares (PLS) or back-propagation artificial neural network (BP-ANN). The results show that the models can be used to predict the moisture, fat content, and storage time rapidly, nondestructively, accurately, and simultaneously. Furthermore, in order to explore the changes of nutrients in leisure dried tofu with the storage time, the storage dynamics of moisture and fat was considered by a using corresponding calibration model.

Analysis of porous structure of potato starch granules by low-field NMR cryoporometry and AFM

Pore size distribution is a crucial structural element affecting the adsorption and diffusion of reagents and enzymes within starch granules. An accurate and credible method of determining the pore size distribution of starch granules especially for smooth ones is therefore required. In this work, low-field NMR cryoporometry (LF-NMRC) was applied to analyze the pore structure of potato starch (PS). The reliability of the LF-NMRC method is verified by comparing with the traditional method, i.e. the low temperature nitrogen adsorption (LT-NA). Both LF-NMRC and LT-NA could characterize the PS pore structure in mesoporous range. However, LF-NMRC has superiority over LT-NA in terms of the distinguishment and determination of pore size distribution approaching to the micropores, gives more accurate and reliable results than LT-NA does. Structural evidences from scanning electron microscope (SEM) and atomic force microscope (AFM) further indicated that the new proposed method is a non-destructive method that does not induce structural changes during sample preparation.

Comparison between synthetic and rosemary-based antioxidants for the deep frying of French fries in refined soybean oils evaluated by chemical and non-destructive rapid methods

Using natural antioxidants instead of synthetics ones has been the tendency for retarding the oil deterioration during repeated deep frying process. Concerning this, the comparison between synthetic tertiarybutyl hydroquinone (TBHQ) and rosemary-based antioxidants in frying French fries was hereby evaluated. The quality and stability of frying oils with rosemary-based antioxidants showed higher efficiency than TBHQ regarding oxidation parameters (i.e., chemical indices, sensory, etc.), where rosmarinic acid (RA) was the most effective, followed by rosemary extracts (RE) and carnosic acid (CA). LF-NMR results were highly correlated (R² = 0.909-0.998) to the change in physicochemical properties tested, where RA could effectively regulate the relaxation spectrum (T₂) change and decrease single component relaxation time (T_2W). The PCA graph of NIRS also revealed the dynamic change of antioxidant effectiveness in accordance with that obtained by chemical methods. Hence, both LF-NMR and NIRS can be expected as rapid and efficient methods for future monitoring the frying process.