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In the current study, the effects of flat sweeping frequency and pulsed ultrasound (FSFPU) application with different frequency modes on the inactivation of polyphenol oxidase (PPO) in strawberry juice were investigated in the temperature range of 40–60 °C. The sweeping frequency modes employed includes single-frequency modes of 22 ± 1, 40 ± 1 kHz, and dual-frequency of 22 ± 1 and 40 ± 1 kHz in simultaneous modes. Results suggested that the inactivation patterns of PPO in strawberry juice all followed the first-order kinetic model (R2 = 0.965–0.997). The D values of PPO during thermal inactivation at 40–60 °C were in the range of 126.5–22.8 min, respectively. Remarkable decreases of the D values of PPO can be observed under the different ultrasound frequency modes. They were 100.1–20.3 min (22 ± 1 kHz), 73.3–18.6 min (40 ± 1 kHz), and 56.9–14.5 min (22/40 ± 1 kHz). The activation energy (Ea) during thermal inactivation was 77.25 kJ/mol, which decreased to 73.65 kJ/mol (22 ± 1 kHz), 62.86 kJ/mol (40 ± 1 kHz), and 60.17 kJ/mol (22/40 ± 1 kHz) during thermosonic inactivation, respectively. The results showed that both thermal and thermosonic treatment could effectively reduce the PPO activity in strawberry juice. Moreover, the effect of PPO inactivation was remarkably enhanced by the FSFPU treatment, and dual-frequency mode ultrasound had the highest effect of PPO inactivation. It can be concluded that flat sweeping frequency and pulsed ultrasound can be used as an efficient and low-cost method to facilitate the inactivation of PPO in strawberry juice.

Stearic acid-rich A. parviflora oil production has remained conventional over the past years despite its socioeconomic importance. Ultrasonication (ULT), microwave irradiation (MIC), and ultrasound-microwave (hybrid technique, ULT-MIC)-assisted extraction parameters were optimized. Their effects on the physicochemical, antioxidative, and structural properties of A. parviflora oil were evaluated. ULT ensured higher oil yield and extraction efficiency of 64.15% and 92.16%, respectively, with a 33.33% reduction in extraction time over the conventional method. Oil extraction yield with MIC and ULT-MIC were solvent dielectric constant, e (polarity) dependent. ULT, MIC, and ULT-MIC enhanced the freshness and stability of A. parviflora oil by reducing its acid and peroxide values significantly. MIC produced oil with high total phenol content (226.60 mg Gallic acid equivalents (GAE)/kg). Ultrasonic action had the highest impact on the seed meal structure. A high yield of edible oil that possesses strong antioxidant activity could be obtained by adopting the ULT-MIC hybrid extraction technique with a polar solvent.

The effects of PMF (5-7 T, 5-30 pulses) on enzyme activity, pH, titratable acidity, soluble solids, color, ascorbic acid, total phenols and antioxidant activity (DPPH radical scavenging activity) of cloudy apple juice were evaluated. PMF inhibited activities of polyphenoloxidase (PPO), peroxidase (POD) and pectinmethylesterase (PME), but PPO was more sensitive to PMF than POD and PME. At the intensity of 6 T with 15 pulses, PPO and POD both exhibited the lowest residual activity (53.22 and 92.96%), while PME showed the lowest residual activity (83.01%) at 7 T with 30 pulses. No significant effect on soluble solids was found under all processing parameters, whereas significant decreases of ascorbic acid were observed at the intensity of 7 T with 5-30 pulses. PMF did not change pH, titratable acidity, color, total phenols and DPPH radical scavenging activity severely. These results suggest PMF can be a potential technology for enzymatic inactivation in apple juice with high retention of quality.

The detrimental health implications of chemical preservatives in fruits have necessitated exploitation of safe and natural alternatives such as edible gums. This work studied shelf-life extension in grape (Pinot noir) under cold storage by xanthan gum (XAN) coatings enriched with ascorbic acid (XANAS) and citric acid (XANCI). Standard scientific methods were used to examine some sensory (color, texture—resilience and hardness), enzyme, anthocyanine and antioxidant activities. Also, the reaction rate mechanism was examined through modeling of selected shelf-life indicators; color change, weight loss, and antioxidants. The results revealed that, Xanthan gum and its acid modified coatings significantly (p 143.18 > 136.49 > 104.5 mg/100 g AEAC corresponding to XAN > XANAS > XANCI > CONTROL. Significantly (p

In this work, alternansucrase enzyme from Leuconostoc citreum SK24.002 was used to produce di-glycosyl-stevioside through acceptor reaction. This was detected by high-performance liquid chromatography (HPLC) and was isolated using AB-8 macroporous resin and semi-preparative HPLC. With the help of mass spectroscopy, 1D NMR (H1 and C13) and 2D NMR (COSY, HMQC, HMBC) the di-glycosyl-stevioside structure was identified to be 13-{[α-D-glucopyranosyl-(1→3)-α-D-glucopyranosyl-(1→6)-β-D glucopyranosyl-(1→2)-β-D-glucopyranosyl]oxy} kaur-16-en-19-oic acid β-D glucopyranosyl eater. In order to increase the modified stevioside (di-glycosyl-stevioside) product and reduce production time, the impact of velocity of shaking on the di-glycosyl-stevioside production was also evaluated, using 75–150 rpm for 24 h at 25 °C. The results showed that the di-glycosyl-stevioside production increased significantly (p

The study investigated the effect of multi-frequency ultrasound treatments including mono-frequency ultrasound (MFU), dual-frequency ultrasound (DFU), and tri-frequency ultrasound (TFU) on the physicochemical, antioxidant potential and microbial quality of tomatoes. The results revealed that various frequencies and modes presented significant (P 1.5 log CFU/g of bacteria, yeast and molds. In general, lycopene content, total colour difference, pigment reflectance, texture, microstructural integrity, and microbial load of tomato decreased in the order of MFU > DFU > TFU due to the increasing cavitation and possible additive effect of multi-frequency ultrasound. Results of the investigation recommend that multi-frequency multi-mode ultrasound washing could retain the quality of tomato. It could effectively be employed for postharvest processing of tomato leading to improvement in physicochemical, antioxidant potential and microbial safety.

Response surface methodology was employed to investigate the effect of sodium hydroxide concentration (X(1): 0.05–0.15 M), sonication time (X(2): 5–15 min), ultrasonic power (X(3): 150–450 W/L), and solid–liquid ratio (X(4): 20–60 g/L) on the optimization of protein extraction from tea residue. Single frequency countercurrent ultrasound (SFCU) was employed to assist the extraction and subsequent hydrolysis of the protein. Optimal extraction conditions were established and response surfaces were generated using mathematical models. There were positive linear and negative quadratic effects of extraction variables on protein yield. The optimal predicted protein yield of 138.9 mg/g was obtained under the optimum conditions of concentration of 0.13 M, extraction time of 13 min, ultrasonic power of 377 W/L and solid–liquid ratio of 51.5 g/L. A model for the degree of hydrolysis of the extraction process was also obtained which gave a predicted and experimental value of 8.4% and 7.5% respectively. Essential amino acid content of 36.7% was obtained under optimal conditions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-018-3407-4) contains supplementary material, which is available to authorized users.

Drying and β-carotenes retention kinetics were predicted using models in relative humidity (RH) drying condition. This was achieved by drying carrot slices using RH-convective hot-air dryer at 60, 70 and 80 °C under RH (10% 20% and 30%) conditions at 2.0 m/s air velocity. Three mathematical models describing thin layer were compared to their goodness of fit in terms of coefficient of correlation (R2), root mean square error (RMSE) and reduced Chi square ($$\chi^{2}$$). The Wang and Singh model could satisfactorily describe RH-convective drying of carrot slices with R2, RMSE and $$\chi^{2}$$ in the ranges of 0.996–0.999, 5.4 × 10−4–9.4 × 10−4 and 0.0150–0.03353 respectively. The results reveal that a range of 3.61–8.2% retention of β-carotene was observed for every 10% increase in RH in various drying air temperature. In summary, higher temperatures were mainly responsible for β-carotenes degradation however this can be mitigated when drying is conducted under higher RH.

The effect of integrating ultrasonic pretreatment with ethanol and Viscozyme in the alkaline extraction of protein from tea residue and the generation of possible by-products such as polyphenols and galacturonic acid was assessed. Four extraction pathways: ethanol, Viscozyme, ultrasound (EVU); water, Viscozyme, ultrasound (WVU); ethanol, water, ultrasound (EWU); and ethanol, Viscozyme, heat (EVH) were employed. EVU pretreatment together with alkaline extraction resulted in the highest protein recovery yield of 80.95% with a purification factor of 8.5. EVU enhanced the functionality of extracted proteins in terms of solubility, foam capacity and stability, and emulsion capacity and stability. Surface hydrophobicity of EVU extracted proteins increased compared to the other treatments. There was an increase in free sulfhydryl and a decrease in disulfide bond contents in all the treatments except EVH. Analysis of Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, non-protein nitrogen content and amino acid content revealed slight modification in the protein advance structure in terms of pretreatment, however, the main peptide chain and amino acid composition were not altered. Yield of 79.25 ± 0.75, 54.7 ± 0.98, and 116.50 ± 6.36 mg/g of polyphenols, galacturonic acid, and total sugars were respectively extracted along the extraction protocol as by-products.

Albumin, globulin, gliadin, and glutelin were fractionated from tea residue and their antioxidant activities were compared. Upon having a significantly (p

Investigating the kinetics of enzyme activities and browning indexes in food are very essential in understanding the enzyme inactivation and browning pigmentation reaction during drying processing. In order to understand and predict accurately the enzyme inactivation and browning pigmentation of banana slices using Relative Humidity (RH)-convective hot air dryer aided by ultrasound (US) pretreatment, this study was conducted. Drying was carried out with 20 kHz frequency of US-pretreatment using three durations (10 20 and 30 min) and RH (10 20 and 30%) conditions at 70 °C and 2.0 m/s air velocity. The kinetic study of both enzyme inactivation and browning pigmentation results were compared to their relevance of fit in terms of coefficient of correlation (R2), the root mean square error (RMSE) and the reduced chi-square (χ2). First order and second-order polynomial kinetic model fitted well for enzyme inactivation and browning indexes respectively. Both enzymes inactivation kinetics and enzymatic browning index (EBI) declined significantly (p

Investigating the kinetics of bioactive and antioxidant compounds in food are very crucial in understanding the degradation reaction during storage and processing. To understand the ameliorative effect of relative humidity (RH) and predict accurately the degradation of bioactive and antioxidant compounds of banana slice using RH-convective hot air dryer, this study was conducted. Drying was investigated under three RH (10, 20 and 30%) and temperatures (60, 70 and 80 °C) at 2.0 m/s air velocity. Two mathematical models describing degradation of food properties were employed and results were compared to their goodness of fit in terms of coefficient of correlation (R2), the root mean square error (RMSE) and the reduced Chi square ( $${\chi ^2}$$ ). First-order model could satisfactorily describe degradation bioactive and antioxidant compounds of drying of banana slices with highest R2, and lowest RMSE and $$~{\chi ^2}$$ . The enthalpy changes were significantly (p

The influences anti-browning agents (citric and ascorbic acids) and relative humidity (RH) on dried banana slices were investigated. Three concentrations (0.5, 1.0 and 1.5% w/v) of each citric and ascorbic acids pretreated banana slices (5 mm) were dried under 75 °C, 10, 30 and 50% RH and 2.0 m/s air velocity in RH-convective hot air dryer. The relationship between the RH with anti-browning agents on drying kinetics, enzymes inactivation, browning index as well as other qualities of banana slices were discussed. Results showed that RH of 10 and 30% achieved 20 and 10% drying time reduction respectively when compared with untreated sample. Contrary, 50% RH increased the drying time by 10%. Results also showed that the resistivity of the enzymes studied follows the order: Peroxidase > Polyphenol oxidase > Ascorbic acid oxidase. Enzymatic browning index was observed to decrease when anti-browning agent and RH increased and decreased respectively. Lower RH (10 and 30%) was in favor of non-enzymatic reduction but 50% RH produced a contrasting result. For color, a significant (p

The effect of ultrasound pretreatment using Single Frequency Counter Current Ultrasound (SFCCU) on the enzymolysis of tea residue protein (TRP) extracted with sodium hydroxide was investigated. The concentration of TRP hydrolysate, enzymolysis kinetics and thermodynamic parameters after SFCCU pretreatment were determined and compared with traditional enzymolysis. The results indicated that both ultrasound assisted and traditional enzymolysis conformed to first-order kinetics within the limits of the studied parameters. Temperature and sonication had affirmative effect on the enzymolysis of TRP with temperature yielding greater impact. Michaelis constant (K M ) in ultrasonic pretreated enzymolysis decreased by 32.7% over the traditional enzymolysis. The highest polypeptide concentration of 24.12 mg ml−1 was obtained with the lowest energy requirement at improved conditions of 50 g L−1 of TRP, alcalase concentration of 2000 U g−1, time of 10 min and temperature of 50 °C for the ultrasonic treated enzymolysis. The values of reaction rate constant (k) for TRP enzymolysis increased by 78, 40, 82 and 60% at 20, 30, 40 and 50 °C, respectively. The thermodynamic properties comprising activation energy (Ea), change in enthalpy (∆H) and entropy (∆S) were reduced by ultrasound pretreatment whereas Gibbs free energy (∆G) was increased.

The effects of ultrasound pretreatments on mass transfer kinetics, microstructure, carotenoid and vitamin C contents of sweet potato were investigated. Sweet potato samples were treated in distilled water with ultrasound (DWU), osmotic dehydration without ultrasound (OD) and ultrasound-assisted osmotic dehydration (UOD). Samples were subjected to ultrasound probe of 2 cm diameter, frequency of 28 kHz at 300 W maximum power at different pretreatment times of 20, 30, 45 and 60 min. The Azuara model used in this study fitted the experimental data well with high coefficient of correlation ranging from 0.92 to 0.98, low values of chi-square ( 70%) in sweet potato samples treated in DWU and UOD.

Microcystin-RR (MC-RR) is a highly acute hepatotoxin produced by cyanobacteria. It is harmful to both humans and the environment. A novel aptamer was identified by the systemic evolution of ligands by exponential enrichment (SELEX) method as a recognition element for determination of MC-RR in aquatic products. The graphene oxide (GO) SELEX strategy was adopted to generate aptamers with high affinity and specificity. Of the 50 aptamer candidates tested, sequence RR-33 was found to display high affinity and selectivity, with a dissociation constant of 45.7 ± 6.8 nM. Aptamer RR-33 therefore was used as the recognition element in a fluorometric assay that proceeds as follows: (1) Biotinylated aptamer RR-33 is immobilized on the streptavidinylated wells of a microtiterplate, and carboxyfluorescein (FAM) labelled complementary DNA is then allowed to hybridize. (2) After removal of excess (unbound) cDNA, sample containing MC-RR is added and incubated at 37 °C for 2 h. (3) Displaced free cDNA is washed away and fluorescence intensity measured at excitation/emission wavelengths of 490/515 nm. The calibration plot is linear in the 0.20 to 2.5 ng·mL−1 concentration range, and the limit of detection is 80 pg·mL−1. The results indicate that the GO-SELEX technology is appropriate for the screening of aptamers against small-molecule toxins. The detection scheme was applied to the determination of MC-RR in (spiked) water, mussel and fish and gave recoveries between 91 and 98 %. The method compares favorably to a known ELISA. Conceivably, this kind of assay is applicable to other toxins for which appropriate aptamers are available.

Biological effect and inactivation mechanism of Bacillus subtilis exposed to pulsed magnetic field (PMF) were investigated. Cell morphology, membrane permeability, release of intracellular proteins and damage of deoxyribonucleic acid (DNA) were monitored. The inactivation effect of PMF treatment on B. subtilis was enhanced with the increase in intensity and pulse number. Scanning electron microscopy (SEM) analysis showed that the PMF treated bacterial cells had rough surfaces and damaged cellular membranes. Flow cytometry measurements showed that the cell membrane permeability increased after the PMF treatment. Leakage of intracellular contents, measured as OD, significantly increased with the increase in PMF intensity and pulsed number. A maximum leakage of cytoplasmic contents was detected at intensity of 3.30 T and 30 pulses. Enterobacterial repetitive intergenic consensus - polymerase chain reaction (ERIC-PCR) fingerprint signaled that the DNA was fragmented after the PMF treatment at the intensity of 3.0 T with 30 pulses and 3.3 T with 10, 20 and 30 pulses. These findings may give clues to the mechanism of bacterial cell death due to the PMF treatment.

Pulsed magnetic field (PMF) technology has emerged as a non-thermal method for inhibition of spoilage microorganism in food. In this study, we evaluate the effect of PMF treatment on the inactivation of Bacillus subtilis. The mechanisms responsible for cell death were also studied using transmission electron microscopy (TEM) and proteome approaches. Results showed that the survival rate of B. subtilis generally decreased with an increase of pulse numbers at the intensity of 3.30 T. The observation of TEM showed damage in cell cytoplasm and cytoplasmic membrane after PMF treatment. Additionally, 18 differentially expressed protein spots were identified by two dimensional gel electrophoresis (2D-GE) and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight (MALDI-TOF/TOF) analysis. The down-regulated outer membrane protein A (OmpA) illustrated that PMF destroyed the cell membrane. Furthermore, Gene ontology (GO) analysis and kyoto encyclopedia of genes and genomes (KEGG) pathway analysis were used to characterize the functions of those proteins. That PMF treatment damaged the membrane component, depressed cellular molecular functions and biological process, and decreased the carbohydrate metabolism and energy metabolism, which explain the death of cells. The presented results give the better view into the proteome of food microorganism and provide insight into the nature of PMF inactivation mechanisms.

The main objective of this research was to study the effects of ultrafine grinding and pulsed magnetic field (PMF) treatment on free gossypol (FG) content in cottonseed meal (CSM). The results revealed that FG content decreased from 831 to 584 mg kg−1 after CSM was ultrafine ground with an airflow crusher. A further decrease of FG content was achieved by processing with PMF. Response surface methodology (RSM) was applied to optimize the process of detoxification, and results showed that the influence of PMF intensity and pulse numbers was remarkable. Removal efficiency increased distinctly with increasing of PMF intensity (50–500 mT) and pulse numbers (10–60) but decreased slightly with increasing of sample weight (0.5–10 g). The relationship between the removal ratio of FG and PMF intensity, pulse numbers, and sample weight all can be expressed with quadratic equations, respectively. The total removal ratio of FG even reached 83.39 % after cottonseed coarse powder (CSCP) was processed with ultrafine grinding and PMF under conditions of PMF intensity (500 mT), pulse number (50), and sample weight (3 g). And the Box–Behnken design (BBD) generated satisfactory mathematical models that accurately explained the behavior of the system, allowing one to predict the removal efficiency of FG from CSM.

Ultrasound pretreatment of protein could improve the angiotensin-I converting enzyme (ACE) inhibitory activity of hydrolysates and by alerting the structure of enzyme substrates. In this research the effects on ACE inhibitory activity and enzymolysis efficiency were explored under the optimum counter flow ultrasound (CFU) pretreatment conditions which obtained from our previous studies. The mechanism was studied by microstructure, nano-mechanical properties and secondary structures of wheat gluten (WG), which measured by scanning electron microscopy (SEM), atomic force microscopy (AFM), and flourier transform infrared spectrum (FTIR). The results showed that the CFU pretreatment resulted in significantly (P

Pretreatment of oat protein with ultrasound showed excellent prospects in increasing the efficiencies of enzymatic hydrolysis and inhibitory activities of peptides against angiotensin converting enzyme (ACE). The mechanism of the ultrasound pretreatment on enhancement of protein hydrolysis rate and the characterization of the enzymolysis process was investigated. The Michaelis-Menten model was used to study the effects of ultrasound on the hydrolysis rate. An ordered sequential bi-substrate reaction mechanism model was applied to describe the characteristics of enzymolysis of the protein with ultrasonic pretreatment. The protein concentration and the enzyme loading were factors in this model. The kinetic parameters of the models were estimated by experimental results and evaluated. The results showed that ultrasonic power, time and enzymolysis time greatly influenced the degree of hydrolysis and ACE inhibitory activities of the peptides. The best conditions for hydrolysis and ACE inhibitory activities were 750 W, 20 min of sonication followed by 60 min of enzymolysis. After the treatment, the hydrolysis rate and the ACE inhibitory activities of peptides were significantly (P

The collagen in Amur sturgeon muscle was isolated using sodium chloride (salt-solubilized collagen, SSC, 3.02%), followed by acetic acid (acid-solubilized collagen, ASC, 31.56%) and then pepsin (pepsin-solubilized collagen, PSC, 58.49%). The collagens appeared to be dense sheet-like film linked by random-coiled filaments under SEM. There was no obvious difference in denaturation temperature (about 33°C) assessed by CD, while the melting temperature of SSC (115.82°C) was significantly lower than ASC and PSC (120.23 and 118.80°C, respectively) determined by DSC. SDS-PAGE showed that the collagens were mainly type I with similar amino acid profiles. FTIR confirmed the triple helical structure of the collagens, and indicated more hydrogen bond in PSC and more intermolecular crosslinks in ASC. These results provide some basis for elucidating the function of collagen in the development of meat texture during postmortem aging and processing.

In this study, the effect of sweeping frequency ultrasound (SFU) treatment on the degree of hydrolysis of zein and the angiotensin I-converting enzyme (ACE)-inhibitory activity of its hydrolysates were investigated. The mechanism through which ultrasonic pretreatment releases peptides with ACE-inhibitory activity was also studied by fluorescence, circular dichroism (CD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Compared to the control, SFU and fixed frequency ultrasound (FFU) increased the degree of zein hydrolysis by approximately 11.5 %. Sweeping frequency ultrasound pretreatment increased ACE-inhibitory activity of zein hydrolysates by 12.3–116.7 % over the control. At 40 ± 2 kHz, SFU-treated zein hydrolysates had 42.9 % ACE-inhibitory activity, representing an increase of 116.7 % over the control. The fluorescence intensity of SFU- and FFU-treated zein was weaker than in untreated zein, indicating that more Phe, Trp, and Tyr residues were exposed outside the polypeptide chains. CD spectra show that SFU treatment resulted in increase in the α-helix content by 3.4 %, and β-sheet, β-turns, and random coils content by 24.4 %. Analyses of microstructure by SEM and AFM revealed that ultrasonic pretreatment ruptured the fine meshwork structure of zein resulting in the appearance of several micro-holes. We conclude that the SFU pretreatment for 40 ± 2 kHz can remarkably raise the degree of zein hydrolysis and ACE-inhibitory activity of the hydrolysates by altering the second structure of zein and rupturing the smooth surface of protein.

The degree of hydrolysis (DH) and angiotensin I-converting enzyme (ACE)-inhibitory activity of vital wheat gluten (VWG) hydrolyzed using Alcalase were investigated using Box-Behnken response surface methodology (RSM). The mean responses were fitted to a second order polynomial to obtain regression equations. The enzyme-substrate ratio and the hydrolysis time increased the DH significantly (p

Short peptides from different sources have been proven to be very efficient inhibitors of angiotensin I-converting enzyme (ACE), an enzyme with a major role in the regulation of blood pressure. In order to obtain ACE-inhibitory peptides from Tenebrio molitor (L.) larva, enzymatic hydrolysis was performed using Alcalase. The hydrolysate (DH 20 %) with the highest ACE inhibition was fractionated into four peaks according to their relative molecular weight by gel filtration on Sephadex G-15. The IC50 value of peak 2 (with the relative molecular weight 180–500 Da) was 0.23 mg/mL, while it was 0.39 mg/mL of hydrolysate before fractionation determined by reversed-phase high performance liquid chromatography (RP-HPLC). Antihypertensive activity of peak 2 was proven by single oral administration to spontaneously hypertensive rats (SHR). Multiple dose oral administration (100, 200, and 400 mg/kg body weight) to SHR led to a significant decrease in blood pressure for peak 2. The reduction of systolic blood pressure even reached 27 mm Hg at 4 h post-administration at a dose of 400 mg/kg body weight. Additionally, further separation and purification of the ACE-inhibitory peptides from peak 2 were performed using RP-HPLC on C18 column. Then a novel peptide Tyr–Ala–Asn was identified by tandem mass spectrometry with an IC50 value of 0.017 mg/mL. The result of research indicates that Tenebrio molitor (L.) larva protein may be a suitable candidate to prepare ACE-inhibitory peptides which could be used for food industry and nutraceuticals.