The ultrasonication-assisted infrared cooking (USIC) on the improvement of texture and flavor of aged Indica rice was evaluated, and the role of ultrasonication was discussed considering starch structures and water status modifications, with varying ultrasonic powers (400-1000 W). Results showed that the moisture content in cooked and stir-fried aged Indica rice was increased, the hydrogen bond freedom and the proportion of immobile water were enhanced by USIC. The amylose content was reduced from 23.17 ± 0.06 g/100 g to 18.04 ± 0.17-19.91 ± 0.13 g/100 g, the relative crystallinity of rice starch declined from 18.32% to 3.32%-4.82%. FTIR spectrum analysis indicated the R1047/1022 cm -1 achieved a lower value (1.08-1.09), starch-protein interactions were weakened, starch-lipid complex formation was aggravated. USIC increased rapidly digested starch (RDS) content but decreased slowly digested starch (SDS) and resistant starch (RS) content. At ultrasonic powers ≥ 800 W, RS content was elevated. The hardness, chewiness, and stickiness of both USIC cooked and stir-fried rice were reduced; however, it presented a firstly decreasing and then increasing trend with the ultrasound power, with the lowest value achieved with the ultrasonic power 600 W. Microstructurally, USIC-treated rice exhibited a sponge-like porous structure with a rougher surface and fissured cross-section. USIC had no negative effect on the oil oxidation of stir-fried rice; the prominent flavor of aged Indica rice from sulfides and nitrogen oxides after cooking was attenuated and balanced by electronic nose analysis. It indicated USIC can serve as a novel approach to enhance the sensory quality of aged rice products.

This study investigated the effect of ultrasonication duration (0-14 min) on oil absorption of infrared fried (IF) potato slices, tracking the crust characteristics and starch structures changes. Results showed that with the assist of ultrasonication, the total oil content (TO) in IF potato slices had a progressively reduction (2.36 %-28.13 %) and the surface penetrated oil content (PSO) was reduced by 2.11 %-38.37 %, with the minimum TO (31.34 g/100 g db) and PSO (21.31 g/100 g db) observed at 8 min of ultrasonication. CLSM observations confirmed the reduction effect on oil absorption was attenuated with excessive ultrasonication (beyond 8 min in this test conditions). This reduction was attributed to ultrasound-facilitated internal moisture migration, retarded early crust formation, decreased volume fraction of large pores (100-250 μm), and increased bulk density of the crust. However, excessive ultrasonication (>8 min) attenuated the oil-reducing effect: it caused overexpansion and fusion of micropores (10-100 μm) and millipores (0.02-10 μm), enhanced crust crispness, which ultimately increased oil potential penetration pathways. At the starch structural level, ultrasonication aggravated the destruction of long- and short-range crystalline structures of crust starch and intensified the accumulation of starch-lipid complexes. Prolonged ultrasonication (>8 min) further led to starch granule fragmentation and destruction, increased connectivity of collapsed pores in the crust, thereby promoting oil absorption. In conclusion, ultrasound-assisted infrared frying (USIF) with a strategic ultrasonication duration can effectively produce low-fat fried potato products, providing theoretical support for oil reduction in high-starch fried foods.

In this study, the synergy effects of ultrasound (US) and dual-enzyme (α-amylase and cellulase, Dual-en) treatment on texture and sensory quality of aged Indica rice were investigated. Results indicated that the US+Dual-en pretreatment significantly reduced intensity of hydrogen bond in or between starch and non-starch biomacromolecules in aged rice, improved the moisture content in cooked and stir-fried rice. Analysis of rice starch showed the amylose content was significantly reduced while the solubility and water holding capacity was increased. FTIR spectrum analysis indicated the relative crystallinity exhibited a significant reduction from 18.23 % to 12.13 % with the absorbance ratio R1047/1022 cm-1 reached the minimum value, and the interactions between proteins and starch were weakened. The D [4, 3] (volume-weighted mean diameter) was reduced from 61.50 μm to 39.70 μm after US+Dual-en treatment, D10, D50, and D90 (corresponding to 10 %, 50 %, and 90 % cumulative volume fractions) were diminished. Although the gelatinization temperature (Tp) increased slightly, the gelatinization enthalpy (ΔH) decreased after ultrasonic or enzymatic treatment, the gelatinization temperature range (ΔT) broadened as well. SEM observations confirmed the destruction on starch granule morphology was aggravated. The hardness, and stickiness of aged Indica rice after cooking and stir-frying was reduced by US+Dual-en pretreatment with diminished oil oxidation and off-odor. Correlation analyses confirmed direct links between starch structural changes and quality enhancements. Combined with sensory evaluation data, the ultrasound-assisted dual-enzyme treatment can be considered as an alternative method to improve the texture and sensory quality of aged Indica rice products.

BACKGROUNDThe structural changes of starch would have a more crucial impact on oil absorption and quality changes in starch-rich fruits and vegetables during frying process with enhanced heat transfer (such as infrared frying). In the present study, the influence of integrated ultrasonic and ethanol (US + ethanol) pretreatment on oil uptake in infrared fried (IF) ginkgo seeds was evaluated regarding modifications in the physicochemical properties of starch. The pretreatment was performed with ultrasonic (40 kHz, 300 W) and ethanol osmotic (95%, v/v) treatment individually or integrated for 40 min.RESULTSThe mass transfer in the pretreatment was facilitated by combined ultrasound and ethanol. The swelling power, solubility, and gelatinization degree of starch was significantly increased. Low-frequency-NMR curves and images revealed that the bound water fraction in ginkgo seeds was increased and the water distribution was homogenized. The results of Fourier transform-infrared spectrum and differential scanning calorimeter revealed that the crystalline regions of starch were reduced and the thermal enthalpy was decreased after US + ethanol pretreatment. The total, surface and structural oil content in IF ginkgo seeds with US + ethanol pretreatment was reduced by 29.10%, 34.52% and 29.73%, respectively. The US + ethanol pretreatment led to a thinner crust layer with increased porosity and smaller-sized pores in the IF ginkgo seeds as observed by stereo microscopy and scanning electron microscopy.CONCLUSIONThe changes in structural and physicochemical properties of starch by combined ultrasound and ethanol affect the crust ratio and pore characteristics in fried high-starch fruits and vegetables, thereby reducing oil absorption. (c) 2024 Society of Chemical Industry.

The effects of integrated ultrasonic infrared frying (USIF) on the oil absorption of apple slices and the oil deterioration were studied with frequency of 28 and 40 kHz, respectively. Results showed that the heat transfer and moisture migration was accelerated by the integrated ultrasound in IF. The soluble Gal-A content and esterification degree of pectin was increased, the damages of pectin crystal structure and chemical structure in side chain was aggravated. These damages to pectin were intensified with higher frequency (40 kHz) of ultrasound. Lower retention of phenols was found in USIF apple slices, but the flavonoids content had no significant change compared to CF samples. USIF samples showed a smoother morphology, and the pore volume and porosity were reduced by ultrasonication applied with 28 kHz but increased with 40 kHz. The largest volume fraction of pores was changed from 100-250 mu m in IF to 0.02-10 mu m and 10-100 mu m by the integrated ultrasound at 28 kHz and 40 kHz samples, respectively. The total oil uptake in USIF samples was reduced by 24.9 %-33.2 % compared to the conventional fried (CF) samples, and achieved the lowest with the frequency of 40 kHz. The surficial and structural oil were also decreased by 39.2 %-51.3 % and 20.9 %-32.3 %, respectively. The peroxide value, acid value, carbonyl value, polar component, and the saturated fatty acids ratio of oil in repeated frying for 16 h was reduced in USIF, especially with ultrasonication 40 kHz. These results indicate that USIF is a promising method for producing novel low-oil apple fries.

Microalgae have been suggested as alternative and sustainable food ingredients due to their nutritional composition, richness in bioactive compounds and their potential to provide essential protein in the face of systemic disturbances. Microalgae powder is an optional dehydrated microalgae product, and its excellent physical properties make it widely utilized in various food products as a nutrient ingredient. Efficient and cost-effective drying and storage methods for microalgae powders heavily affect their overall physical properties, quality index, production cost and stability. This chapter describes the characteristics of commonly used and the latest progress in drying technologies, and critically evaluates the feasibility of their use to produce microalgae powders with optimal physical properties. The suitability of each drying method depends on the properties of the microalgae suspension, the required process design, the quality of the end products, and the related capital and production costs. The storage methods, which combined the effects of hypothermia and hypoxia, will be beneficial to maintain overall quality throughout the storage period. Furthermore, the trends and challenges that could further develop edible microalgae powders as environmentally sustainable diets are proposed, showing further commercial prospects for the purpose.

BACKGROUND:The crust characteristics of fried crisps determine their oil absorption. Starch structures, as the main components of fried starchy fruits and vegetables, influence their crust formation and properties. This study investigated the reduction of oil uptake and acrylamide content in infrared-fried (IF) banana slices by modifying starch structures at varying infrared power levels. RESULTS:Infrared heating improved heat transfer and surface moisture removal in fried banana slices. It facilitated crust formation in the IF samples and produced increased crust uniformity, crust ratio, and hardness. Analysis of the porous properties showed that the volume fraction of pores sized 100-250 μm was reduced in IF samples but the proportion of pores with a diameter ranging from 0.02 to 10 μm was increased. Infrared frying reduced the total oil uptake, surface oil, and structural oil content in banana slices, and each of these measures decreased as infrared power levels increased. Characterization of the starch structures suggested that the damage to the crystalline structure was increased in IF samples and more starch-lipid complexes were generated, which would be responsible for the formation of a denser and thicker crust. The acrylamide content in the IF sample was reduced, as determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). CONCLUSION:Modifications to starch structures (crystalline structures and chemical structures) play a crucial role in oil absorption in fried starchy fruits and vegetables. Infrared frying can be used as an alternative method to produce low-fat fruits and vegetable crisps with reduced acrylamide content. © 2024 Society of Chemical Industry.

There is a development trend from qualitative towards quantitative analysis for tunnel stability. The widely accepted convergence-confinement method (CCM) provides a quantitative framework for tunnel stability analysis, while the conventional CCM based on closed-form functions is essentially an ideal model without considering the tunnel section shape and rock weight in plastic zone. Herein, based on the CCM framework, a quantitative analysis procedure formulated through numerical simulations for more practical situations was systematically proposed to calculate the safety factor of spray-anchor support system in non-circular tunnel. Besides, similarities and differences between the most widely used Hoek-Brown (HB) and equivalent Mohr-Coulomb (EMC) criteria were considered for practical reference. The proposed method was utilized to conduct quantitative analysis of LDPs, mechanical responses of surrounding rock and safety factors for four typical tunnels, and the consistency between tunnels based on HB criterion (TBHBC) and EMC criterion (TBEMCC) was analyzed. The results indicated that the maximum radial convergence of LDP, plastic zone area, and safety factor of TBEMCC were 34.54%, 37.29%, and 47.71% lower than those of TBHBC respectively. The reasons for differences between results were revealed. The spatial effect induced by the face excavation of TBEMCC was weakened as compared to TBHBC, leading to a drop of LDP. Consequently, the safety factor was underestimated. The method systematically provided an effective tool for quantitative stability analysis and design optimization of support system for an underground excavation.

The aim of this research was to develop a simple, rapid, sensitive, high-throughput detection method for foodborne Escherichia coli (E. coli) O157:H7 based on the aptamer-modified gold nanoparticles@macroporous magnetic silica photonic microsphere (Au@MMSPM). Such Au@MMSPM array system for E. coli O157:H7 not only integrated sample pretreatment with rapid detection, but also showed highly enhanced effect to develop a highly sensitive SERS assay. The established SERS assay platform gave a wide linear detection range (10-106 CFU/mL) and low limit of detection (2.20 CFU/mL) for E. coli O157:H7. The whole analysis time including sample pretreatment and detection was 110 min. This SERS-based assay platform provided a new high-throughput, highly sensitive and fast detection technology for monitoring E. coli O157:H7 in real samples from the fields of food industry, medicine and environment.

A quick preparation of octenylsuccinylated (OS)-ginkgo seed starch was proposed by lipase-coupling esterification within 30 min, and the physicochemical and emulsifying properties of OS-ginkgo seed starch were evaluated. High-performance liquid chromatography results revealed that ginkgolic acid in ginkgo seed starch was too low to be detected, which improved the biosafety and application range of OS-ginkgo seed starch. The degree of substitution (DS) of OS-ginkgo starch varied from 0.006 to 0.0169 depending on the lipase concentration increased from 0% to 1% (w/w, based on the volume of starch solution), and the reaction efficiency obtained the highest value of 68.5% at the lipase concentration of 1%. Fourier transform infrared spectra of OS-ginkgo seed starch confirmed ester carbonyl splicing in the starch molecular with the characteristic peaks at 1722 and 1567 cm(-1). Scanning electron microscopy observations revealed that the esterification occurred mainly in the amorphous regions with slight morphological modification. X-ray diffractions suggested that no crystal change occurred on the starch granule. The thermal analysis revealed that OS-ginkgo seed starch showed a lower temperature and endothermic enthalpy for gelatinization, and presented enhanced and DS-dependent emulsifying properties and in vitro antidigestion properties. Practical Application Results indicated that OS-ginkgo seed starch prepared by lipase-coupling esterification would be an alternative emulsion stabilizer for encapsulation and delivery of hydrophobic components. This study would provide an alternative method for the efficient and economical production of OS-ginkgo seed starch, thereby broadening its application in commercial exploitation.

The influence of infrared frying (IF) on the physicochemical properties of fried apple slices and the oil deterioration was investigated, considering conventional frying (CF) as a reference. IF had a more favorable impact on the heating rate and thermal efficiency, which subsequently resulted an accelerated moisture removal rate. The oil uptake in infrared-fried apple slices were reduced by 12.9%-17.3%, when compared to the CF, as attributed to the denser and smoother morphological microstructure. The color of apple slices was better preserved in IF and the total phenolic and flavonoid contents had a higher retention rate with the optimal infrared power (2000 W in this study). Additionally, infrared frying was proved to be a promising technology to slow down the oil deterioration rate as was observed from lower values of acid value, and carbonyl value, which was also supported by the results of gas chromatography, FT-IR, and LF-NMR analysis.

BACKGROUND Lotus seed protein (LSP) was extracted from lotus seed and used to encapsulate curcumin with or without complexing with pectin. The physicochemical properties of LSP-based microcapsules, including solubility, stability, and in vitro sustained release, were determined. The mechanism of interaction between curcumin, LSP, and pectin was revealed. RESULTS The encapsulation efficiency of curcumin was found to depend on LSP concentration and was highest (86.32%, w/w) at 50 mg mL(-1). The curcumin in curcumin-LSP and curcumin-LSP-pectin powder particles achieved a solubility of 75.15% and 81.39%, respectively, which was a remarkable enhancement. The microencapsulation with LSP and LSP-pectin matrix showed a significant improvement in the antioxidant activity, photostability, thermostability, and storage stability of free curcumin. The microencapsulated curcumin showed sustained control release at the gastric stage and burst-type release in the subsequent intestinal stage, presenting cumulative release rates of 64.3% and 72.4% from curcumin-LSP and curcumin-LSP-pectin particles after gastrointestinal digestion. The LSP-pectin complex produced microcapsules with higher solubility, smaller particle size, enhanced physicochemical stability, and increased bioaccessibility. Fourier transform infrared, circular dichroism spectra, and differential scanning calorimetry data indicated that the encapsulated curcumin interacted with LSP and pectin mainly through hydrogen bonding, hydrophobic, and electrostatic interactions. CONCLUSION This work shows that LSP can be an alternative encapsulant for the delivery of hydrophobic nutraceuticals with enhanced solubility, stability, and sustained release. The results may contribute to the design of novel food-grade delivery systems based on LSP vehicles, thereby broadening the applications of LSP in the fields of functional food. (c) 2021 Society of Chemical Industry.

Summary In this study, the lutein was microencapsulated by complex coacervation with gelatin and OSA starch as vehicles, and the physicochemical and in vitro release properties of the microcapsules were evaluated followed by the spray drying or freeze‐drying method. Preliminary assays of coacervation indicated that a higher encapsulation efficiency was obtained at the gelatin/OSA starch volume ratio of 5:4 and the core/wall material volume ratio of 1:8 (v/v) followed by the spray‐drying method. The lutein‐gelatin‐OSA microcapsules had a higher solubility, antioxidant activity, thermostability, relative humidity stability and sustained in vitro release compared to the free lutein. Fourier transform infrared data indicated that the encapsulated lutein interacted with gelatin and OSA starch was mainly through hydrogen bonding, hydrophobic and electrostatic interactions. The freeze‐dried microcapsule was observed with a more regular shape, smaller particle size in morphology and confirmed with better thermal stability from the differential scanning calorimetry results while the spray‐dried microcapsules obtained a higher cumulative release rate of lutein and higher antioxidant activity. The results of this study are expected to contribute to the design and commercial application of gelatin‐OSA starch complex‐based delivery systems for hydrophobic nutraceuticals with desired physicochemical properties and digestive performance.

Surface modified pH-responsive porous silicon (PSi) carriers were developed for efficient delivery of lutein. PSi particles were prepared by the electrochemical etching method and modified with two chemical groups: hydroxyl and octadecyl silane, respectively. Chitosan (CS) was used for coating of PSi to ensure pH-responsive release. The loading conditions, release properties, cytotoxicity and toxicity were investigated. The highest loading percentage of lutein could be obtained with oxidized PSi and the structure of the microparticles was characterized by Fourier transform-infrared spectroscopy. The surface area and pore size of the microparticles were obtained from the N2 adsorption-desorption isotherm. The CS-PSi-Lut microparticles showed the minimum surface area of 220.30 m2 g-1 and a relatively larger average pore width of 179.00 Å. In vitro release experiments showed a pH-responsive and controlled release of lutein, with the fastest release rate and highest cumulative release rate of 97% under acidic conditions (pH 5.0) within 7 h. PSi, chitosan and lutein showed synergistic toxic effects, and the CS-PSi-Lut microparticles could effectively inhibit the proliferation of HT-29 cells in a dose-dependent manner, with an inhibition rate of 77% when the lutein concentration reached 40 μg mL-1. The in vivo toxicological evaluation of CS-PSi-Lut microparticles indicated good biocompatibility in the range of experimental doses. The chitosan-coated oxidized PSi capable of delivering bioactive compounds in a targeted and controlled manner provides a novel platform for the development and application of lutein.

Frying is one of the most common units in food processing and catering worldwide, which involves simultaneous physicochemical and structural changes. However, the problems of traditional frying technology, such as low thermal utilization and poor processing efficiency, have been gradually exposed to industrial production. In this paper, strategies of applying physical fields, such as pressure field, electromagnetic field, and acoustic field in frying technology separately or synergistically with improved efficiency and quality attributes are reviewed. The role of physical fields in the frying process was discussed with modifications in heat and mass transfer and porous structures. The effects of physical fields and their processing parameters on moisture loss kinetics, oil uptake, texture, color, and nutrients retention of fried food are introduced, respectively. Recent advances in multi-physical field-based frying techniques were recommended with synergistic benefits. Furthermore, the trends and challenges that could further develop the multi-physical field-based frying techniques are proposed, showing further commercial prospects for the purpose. The application of physical fields has brought new inspiration to the exploitation of efficient and high-qualified frying technologies, while higher technical levels and economic costs need to be taken into consideration.HighlightsThe role of physical fields in pretreatments and frying process were reviewed.The mechanism of physics fields on frying efficiency and quality was summarized.The physicochemical and microstructure changes by physics fields were discussed.The synergy of physical fields in frying technology were outlined.The trends for further multi-physical field-based frying techniques were proposed.

Microwave-assisted vacuum frying (MVF) was reported to improve the processing efficiency with the microwave heating method, while the oil uptake of products also needs to be reduced to enhance the overall quality. In this research, the effectiveness of osmotic dehydration and coating pre-treatment on reducing the oil absorption of MVF potato chips were evaluated with the verification of empirical models. Meanwhile, the effects of different pre-treatment on dielectric properties, moisture loss kinetics, texture, and color of MVF samples were analyzed. Results suggested that the oil uptake of MVF products was reduced by 16.6%–31.4% and 27.8% with osmotic dehydration pre-treatment in 1%–5% NaCl and 2.5% MSG solution, which is related to the enhanced moisture removal induced by the dielectric property improvement. The coating pre-treatment with 25% maltodextrin, 1.0% CMC-Na, and 1.5% chitosan had no negative effect on the dielectric properties and the moisture loss rate of samples during frying. While the oil absorption of MVF products was reduced by 53.5%, 36.8%, and 15.2% respectively due to the colloidal layer barrier formed by the coating pre-treatment. The empirical model provided better fits for the oil absorption process of MVF samples with osmotic dehydration pre-treatment, while it is not applicable to the coating pre-treatment. The hardness and color of MVF products was generally improved by the osmotic dehydration and coating pre-treatment. The osmotic dehydration and coating pre-treatment can be utilized as an alternative de-oiling method for MVF potato chips, but the law and mechanism of reducing the oil uptake are differs.

Presently, the effectiveness of combined ultrasonic and ethanol (US + ethanol) pre-treatment was evaluated with an aim to reduce the oil uptake and enhance the frying efficiency of deep-fried apple slices. The US + ethanol pre-treatment was conducted by immersing apple slices in 95% ethanol and ultrasonic treatment (40 kHz, 300 W) for 30 min. Results revealed that the permeability of cells was greatly increased and the mass transfer during the pre-treatment was significantly enhanced by the US + ethanol pre-treatment. Subsequently, the heat transfer and moisture loss kinetics of fried apple slices were significantly improved by the US + ethanol pre-treatment. The oil uptake was achieved the lowest value and reduced by 34.5% and 28.2% in the fried samples pre-treated by 95% ethanol and US + ethanol, respectively, compared with the untreated samples (60.5 g/100 g db). The appearance, total phenolic and flavonoid contents in fried apple slices were also improved by the US + ethanol pre-treatment. The morphology observation revealed that the US + ethanol pre-treatment induced a denser and smoother surface and more micron-sized pores on the crust of fried apple slices. Conclusively, the US + ethanol pre-treatment would be a promising method for the reduction of oil uptake in fried fruits and vegetables with an enhanced frying efficiency.

Rock bolts are one of the primary underground support systems utilized to stabilize the rock mass surrounding the opening of an excavation by transferring the load from the surrounding rock to the more stable rock mass further from the excavation. Modelling fully grouted rock bolts has been the focus of many researchers due to the difficulties associated with capturing the interaction mechanism(s) concerning the interface between the rebar and the grout as well as the grout and the rock at the micro-scale. In this paper, two-dimensional (2D) numerical simulations have been conducted in order to model the behaviour of fully grouted rock bolts (FGRBs) during axial pullout tests. Joint parameters of the rebar-grout interface (i.e. shear stiffness, normal stiffness and cohesion) are investigated as well as grout parameters (i.e. Poisson’s ratio and Young’s modulus) in terms of the influence on the rock bolt behaviour. The results indicate that the Young’s modulus of the grout and joint shear stiffness have significant influences on the overall behaviour and performance of the FGRB system. On the basis of these results, the upper and lower limit of strain distribution along with the rock bolt is determined. These results are also compared to the nominally identical axial pullout tests of rock bolts that have been conducted in the laboratory as part of the physical testing components of the overall research program. RÉSUMÉ Les boulons d'ancrage sont l'un des principaux systèmes de souterrain utilisés pour stabiliser la masse rocheuse entourant l'ouverture d'une excavation en transférant la charge de la roche environnante vers la masse rocheuse plus stable plus loin de l'excavation. La modélisation de boulons de roche entièrement jointoyés a été au centre de nombreux chercheurs en raison des difficultés associées à la capture du ou des mécanismes d'interaction concernant l'interface entre les barres d'armature et le coulis ainsi que le coulis et la roche à la micro-échelle. Dans cet article, des simulations numériques bidimensionnelles (2D) ont été menées afin de modéliser le comportement des boulons de roche entièrement injectés (FGRB) lors d'essais de retrait axial. Les paramètres communs de l'interface barres d'armature (c.-à-d. La rigidité au cisaillement, la rigidité et la cohésion normales) sont étudiés ainsi que les paramètres du coulis (c.-à-d. Le coefficient de Poisson et le module d'Young) en termes d'influence sur le comportement du boulon d'ancrage. Les résultats indiquent que le module d’Young du coulis et la rigidité au cisaillement des joints ont une influence significative sur le comportement et les performances globales du système FGRB. Sur la base de ces résultats, la limite supérieure et inférieure de la distribution des déformations avec le boulon d'ancrage a été déterminée. Ces résultats sont également comparés à des essais de retrait axial des boulons d'ancrage nominalement identiques qui ont été menés en laboratoire dans le cadre des éléments d'essai physique du programme de recherche global.

The effects of low-frequency ultrasonic pre-treatment in water/oil medium simulated system on the improved processing efficiency and quality of microwave-assisted vacuum fried potato chips were investigated. The water medium system (distilled water and 5% NaCl osmotic solution) and oil medium system (90 degrees C) were designed with different power levels of ultrasound to simulate the ultrasonic conditions. Results showed that the changes of moisture content, water loss, solid gain and dielectric properties of potato slices were facilitated by the ultrasonic treatment. LF-NMR analysis showed the binding force between the moisture and structure in the material was significantly (p < 0.05) weakened. The changes become greater with the increase of ultrasonic power levels. Microscopic channels and disruptions were induced on the microstructure by the ultrasonic treatment. The effective moisture diffusivity of vacuum fried (VF) potato chips was increased by about 56.2%-67.0% and 53.9% with the combination of microwave energy and the ultrasonic pre-treatment in water and oil medium simulated system, respectively. The oil uptake, hardness, shrinkage, total color change and water activity of vacuum fried samples were significantly (p < 0.05) decreased by the assist of microwave energy combined ultrasonic pre-treatment.

The ultrasonic microwave-assisted vacuum frying (USMVF) was properly designed and tested as a novel frying technique for potato chips at low frying temperature in this work. The USMVF was carried out by the combination of ultrasound and microwave in the vacuum frying to shorten the frying time and improve the quality of products. Two frying temperatures (90°C and 100°C) were comparatively analyzed both in USMVF and microwave-assisted vacuum frying (MVF). Based on the analysis of drying kinetics and quality assessment, the USMVF markedly increased the moisture evaporation kinetics and effective moisture diffusivity, reducing 20–28% of the drying time compared with the MVF, especially at lower frying temperature. The oil uptake of fried potato chips was reduced in the USMVF with low frying temperature. The texture properties (crispness) and color of fried potato chips were greatly improved by the combination of ultrasound in MVF. The energy consumption in USMVF was also decreased compared to that in MVF, decreasing 20.4–24.7% depending on the frying temperature in this test. A more porous microstructure in USMVF samples was observed by SEM and helped to explain the effects of ultrasound. The drying data (moisture ratio versus time) were successfully fitted to the Logarithmic model.