Study the impact of ultra-sonication and pulsed electric field on the quality of wheat plantlet juice through FTIR and SERS

Pulsed electric field (PEF) and Ultrasound (US) are commonly used in food processing. We investigated the combined impact of pulsed electric field (PEF) and ultrasound (US) on the wheat plantlet juice. When compared with the individual treatments, the highest values of total phenolics, total flavonoids, chlorophyll, ORAC assay, and DPPH activities were obtained using the combined (US + PEF) methods. The US + PEF significantly decreased the peroxidase and polyphenol oxidase activities from 0.87 to 0.27 Abs min⁻¹ and 0.031–0.016 Abs min⁻¹. Also, the synergistic application significantly lowered the yeast and mold (3.92 to 2.11 log CFU/mL), E. coli/Coliform (1.95 to 0.96 log CFU/mL), and aerobics (4.41 to 2.01 log CFU/mL). Furthermore, Fourier Transform Infrared (FT-IR) and surface-enhanced Raman spectroscopy (SERS) was used to analyzing juice quality. Gold nanoparticles (AuNPs) were used as the SERS substrates, which provided stronger Raman peaks for the samples treated with US + PEF methods. The FT-IR analysis showed significant enhancement of the nutritional molecules. The enhanced quality of wheat plantlet juice combined with lower yeast and mold suggests the suitability of integrated methods for further research and applications.     

Design consideration and modelling studies of ultrasound and ultraviolet combined approach for shelf-life enhancement of pine apple juice

Although both ultraviolet (UV) radiation and ultrasound (US) treatment have their capabilities in microbial inactivation, applying any one method alone may require a high dose for complete inactivation, which may affect the sensory and nutritional properties of pineapple juice. Hence, this study was intended to analyse and optimise the effect of combined US and UV treatments on microbial inactivation without affecting the selected quality parameters of pineapple juice. US treatment (33 kHz) was done at three different time intervals, viz. 10 min, 20 min and 30 min., after which, juice samples were subjected to UV treatment for 10 min at three UV dosage levels, viz. 1 J/cm², 1.3 J/cm², and 1.6 J/cm². The samples were evaluated for total colour difference, pH, total soluble solids (TSS), titrable acidity (TA), and ascorbic acid content; total bacterial count and total yeast count; and the standardization of process parameters was done using Response Surface Methodology and Artificial Neural Network. The results showed that the individual, as well as combined treatments, did not significantly impact the physicochemical properties while retaining the quality characteristics. It was observed that combined treatment resulted in 5 log cycle reduction in bacterial and yeast populations while the individual treatment failed. From the optimization studies, it was found that combined US and UV treatments with 22.95 min and1.577 J/cm² ensured a microbiologically safe product while retaining organoleptic quality close to that of fresh juice.     

Low intensity ultrasound as a pretreatment to drying of daylilies: Impact on enzyme inactivation,color changes and nutrition quality parameters

Effects of thermal and low intensity ultrasound combined with heat (LIUH) pretreatment prior to microwave vacuum drying on enzyme inactivation, color changes and nutrition quality properties of dried daylilies were investigated. The peroxidase (POD), ascorbic acid oxidase (AAO) and polyphenoloxidase (PPO) thermal and LIUH (0.2 and 0.4 W/cm²) inactivation were determined and compared at 70, 80 and 90 °C. Significant reduction in the POD, AAO and PPO activity was seen in daylilies after an ambient LIUH pretreatment than thermal pretreatment. POD, AAO and PPO thermal and LIUH inactivation followed the first order kinetics. LIUH pretreatment had a more positive influence on maintaining color of dried daylilies than thermal pretreatment. Furthermore, LIUH pretreatment resulted in a significant increase in chlorophylls, carotenoids (lutein, zeaxanthin and β-carotene), and a decrease in degree of browning and 5-hydroxymethylfurfural (HMF) when compared with thermal pretreatment. The antioxidant activity and contents of several nutritional components of dried daylilies pretreated by LIUH were also higher than that of dried daylilies pretreated by thermal pretreatment. This study provides a basis for the design of LIUH conditions to control vegetables browning and color changes prior to drying processing.     

Enhancement of biogas production from individually or co-digested green algae Cheatomorpha linum using ultrasound and ozonation treated biochar

This paper proposes the use of modified biochar, derived from Sawdust (SD) biomass using sonication (SSDB) and Ozonation (OSDB) processes, as an additive for biogas production from green algae Cheatomorpha linum (C. linum) either individually or co-digested with natural diet for rotifer culture (S. parkel). Brunauer-Emmett-Teller (BET), Fourier-Transform Infrared (FTIR), thermal-gravimetric (TGA), and X-ray diffraction (XRD) analyses were used to characterize the generated biochar. Ultrasound (US) specific energy, dose, intensity and dissolved ozone (O₃) concentration were also calculated. FTIR analyses proved the capability of US and ozonation treatment of biochar to enhance the biogas production process. The kinetic model proposed fits successfully with the data of the experimental work and the modified Gompertz models that had the maximum R² value of 0.993 for 150 mg/L of OSDB. The results of this work confirmed the significant impact of US and ozonation processes on the use of biochar as an additive in biogas production. The highest biogas outputs 1059 mL/g VS and 1054 mL/g VS) were achieved when 50 mg of SSDB and 150 mg of OSDB were added to C. linum co-digested with S. parkle.     

Inactivation of foodborne pathogens based on synergistic effects of ultrasound and natural compounds during fresh produce washing

Ultrasound has potential to be used for disinfection, and its antimicrobial effectiveness can be enhanced in presence of natural compounds. In this study, we compared the antimicrobial effects of ultrasound at 20 kHz (US 20 kHz) or 1 MHz (US 1 MHz) in combination with carvacrol, citral, cinnamic acid, geraniol, gallic acid, lactic acid, or limonene against E. coli K12 and Listeria innocua at a constant power density in water. Compared to the cumulative effect of the individual treatments, the combined treatment of US 1 MHz and 10 mM citral generated >1.5 log CFU/mL additional inactivation of E. coli K12. Similarly, combined treatments of US 1 MHz and 2 mM carvacrol (30 min), US 20 kHz and 2 mM carvacrol, 10 mM citral, or 5 mM geraniol (15 min) generated >0.5–2.0 log CFU/mL additional inactivation in L. innocua. The synergistic effect of citral, as a presentative compound, and US 20 kHz treatment was determined to be a result of enhanced dispersion of insoluble citral droplets in combination with physical impact on bacterial membrane structures, whereas the inactivation by US 1 MHz was likely due to generation of oxidative stress within the bacteria. Combined ultrasound and citral treatments improved the bacterial inactivation in simulated wash water in presence of organic matter or during washing of inoculated blueberries but only additive antimicrobial effects were observed. Findings in this study will be useful to enhance fresh produce safety and shelf-life and design other alternative ultrasound based sanitation processes.     

The inactivation kinetics of polyphenol oxidase in mushroom (Agaricus bisporus) during thermal and thermosonic treatments

The effect of thermal and thermosonic treatments on the inactivation kinetics of polyphenol oxidase (PPO) in mushroom (Agaricus bisporus) was studied in 55–75 °C temperature range. In both the processes, the inactivation kinetics of PPO followed a first-order kinetics (R² = 0.941–0.989). The D values during thermal inactivation varied from 112 ± 8.4 min to 1.2 ± 0.07 min while they varied from 57.8 ± 6.1 min to 0.88 ± 0.05 min during thermosonic inactivation at the same temperature range. The activation energy during thermal inactivation was found to be 214 ± 17 kJ/mol, while it was 183 ± 32 kJ/mol during thermosonic inactivation. The inactivating effect of combined ultrasound and heat was found to synergistically enhance the inactivation kinetics of PPO. The D values of PPO decreased by 1.3–3 times during thermosonic inactivation compared to the D values of PPO during thermal inactivation at the temperature range. Therefore, thermosonication can be further developed as an alternative to “hot break” process of mushroom.     

Synergistic bactericidal effect of ultrasound combined with citral nanoemulsion on Salmonella and its application in the preservation of purple kale

In this study, a novel citral nanoemulsion (CLNE) was prepared by ultrasonic emulsification. The synergistic antibacterial mechanism of ultrasound combined with CLNE against Salmonella Typhimurium and the effect on the physicochemical properties of purple kale were investigated. The results showed that the combined treatment showed obviously inactivate effect of S. Typhimurium. Treatment with 0.3 mg/mL CLNE combined with US (20 kHz, 253 W/cm²) for 8 min reduced S. Typhimurium populations in phosphate-buffered saline (PBS) by 9.05 log CFU/mL. Confocal laser scanning microscopy (CLSM), flow cytometry (FCM), protein and nucleic acid release assays showed that the US combination CLNE disrupt the integrity of S. Typhimurium membranes. Reactive oxygen species (ROS) and malondialdehyde (MDA) detection indicated that US+CLNE exacerbated oxidative stress and lipid peroxidation in cell membranes. The morphological changes of cells after different treatments by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) illustrated that the synergistic effect of US+CLNE treatment changed the morphology and internal microstructure of the bacteriophage cells. Application of US+CLNE on purple kale leaves for 6 min significantly (P < 0.05) reduced the number of S. Typhimurium, but no changes in the physicochemical properties of the leaves were detected. This study elucidates the synergistic antibacterial mechanism of ultrasound combined with CLNE and provides a theoretical basis for its application in food sterilization.     

The disinfection effect of a novel continuous-flow water sterilizing system coupling dual-frequency ultrasound with sodium hypochlorite in pilot scale

In this paper, a self-designed novel continuous-flow water disinfection system coupling dual-frequency ultrasound (US) with chemical disinfectant sodium hypochlorite (NaClO) was tested in a pilot scale using a simulated effluent containing Bacillus subtilis (B. subtilis), one of the indicators of water treatment efficiency. A suspension having a B. subtilis concentration of approximately 10⁴ CFU/mL was introduced into the system to (1) investigate disinfection efficiency of US pretreatment with NaClO (US + NaClO) and simultaneous US and NaClO (US/NaClO) disinfection under different single frequencies; (2) further examine the disinfection efficiency of these two processes with dual-frequency US; and (3) identify dosage reduction of chlorine in this disinfection system. The results demonstrated that lower dual-frequency (17 kHz + 33 kHz) US pretreatment with NaClO disinfection and simultaneous higher dual-frequency (70 kHz + 100 kHz) US and NaClO were beneficial to bacterial inactivation in terms of sterilizing efficiency. It has also been observed that US pretreatment with lower combination of 17 + 33 kHz frequencies showed better enhancement in which log reduction reached to 3.82 after 10 min chlorine reaction (chlorine alone was 0.22 log reduction), nearly 1 log reduction higher than single frequencies at the same constant power. Consequently, at equivalent power dissipation levels, US of lower frequencies combination pretreatment with NaClO disinfection performed such a promising process that one-thirds (from 12 mg/L NaClO reduced to 8 mg/L NaClO) of the required NaClO dosage was reduced for the ideal disinfection efficiency of 4 log reduction, namely 100% disinfection. And the utilization efficiency of NaClO was increased from 37.67% to 85.25% in 30 min of treatment time using an optimized combination of pretreatment and chlorination.     

Effect of ultrasound combined with ultraviolet treatment on microbial inactivation and quality properties of mango juice

This work explored the effect of ultraviolet-assisted ultrasound (US-UV) as an emerging non-thermal sterilization technology on mango juice in aspects of microbial growth and quality changes. The juice in the ice bath was subjected to US-UV treatment at different US powers (0–600 W) and times (0–40 min), and no pathogen bacteria could be detected after treatment, while the physicochemical features (particle size, suspension stability, color, content of total polyphenols, carotenoids, sugar, reducing sugar and protein) and antioxidant ability of treated juice was preserved or improved to some extent. Based on these results, we further validated its positive effects on the nutritional value (content of ascorbic acid and soluble dietary fiber, antioxidant ability) and quality parameters (titratable acid, sugar acidity, total soluble solids, rheological behavior, metal elements) of mango juice treated at the optimal US parameter (10 min, 600 W); Not only the inactivation of polyphenol oxidation enzyme, peroxidase and pectin methylesterase was achieved but also the treated juice has a significant different volatile profile compared with the fresh juice, which might offer the better color, texture, and smell. Importantly, through the HPLC-MSD-Trap-XCT (phenols) and UPLC-Q Exactive Orbitrap-MS (carotenoids) study, the US-UV treatment will not cause difference on compounds composition, but it was responsible for changes in content of individual compounds, especially the all-trans-β-carotene, became the main component of carotenoids in processed mango juice (increased from 43.72% to 75.15%, relative content), and the oxygenated carotenoids (xanthophylls) are highly sensitive to the US (reduced from 50.96% to 4.85%) while the carotenes show a strong resistance to the US (increased 49.04% to 95.15%). Thus, the overall safety and quality of mango juice were enhanced while the sensory characteristics remained stable, suggesting that this non-thermal combination sterilization processing may successfully be implemented in the commercial processing of mango juice.     

Developing ultrasound-assisted hot-air and infrared drying technology for sweet potatoes

The influence of ultrasound (US) pretreatments combined with infrared (IRD) and hot-air (HAD) drying on drying kinetics, mathematical modeling, bioactive compounds (antioxidant activities, Vitamin C, phenolics, and flavonoid contents), qualitative properties (β-carotene, total carotenoids, color indexes, textural profile), enzyme inactivation, and exergetic analysis of sweet potatoes. The US pretreatment at 40 kHz combined with IRD and HAD (70 °C) significantly lessened the drying time and water contents. Besides, it did not affect the sweet potato's bioactive components and other quality-related attributes. The samples’ activation energy (E_a) ranged from 17.60 to 29.86 kJ/mol for both dryers, with R² (0.999–0.9809). Control samples had the highest specific energy consumption (SEC) due to the extended drying period, whereas ultrasound (40 kHz) treated samples had the lowest SEC during HAD and IRD at 80 °C. The thermodynamic parameters indicated that increasing the drying temperature lowers the enthalpy and Gibbs free energy, while entropy resulted in negative values. HAD had better textural qualities (hardness and resilience). The US pretreatments followed by HAD or IRD may lead to an energy-efficient method with acceptable quality maintenance.     

Ultrasonic treatment decreases Lyophyllum decastes fruiting body browning and affects energy metabolism

Lyophyllum decastes is a common mushroom that is prone to browning during prolonged storage. In this study, the effects of ultrasonic treatment on metabolic gene expression, enzyme activity, and metabolic compounds related to L. decastes browning were investigated. Treatment of the fruiting body at 35 kHz and 300 W for 10 min reduced the browning index of L. decastes by 21.0 % and increased the L* value by 11.1 %. Ultrasonic treatment of the fruiting body resulted in higher levels of total phenols, flavonoids, and 9 kinds of amino acid with catalase (CAT) and peroxidase (POD) activities maintained at high levels. Higher cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), phosphofructokinase (PFK), and pyruvate kinase (PK) activities may be ascribed to increased antioxidant capacity. Moreover, ultrasonication retained higher adenosine triphosphate (ATP) concentrations with an increased energy charge, while there were lower levels of adenosine diphosphate (ADP) and reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD⁺), respectively. Meanwhile, lower lignin contents were observed, along with retarded polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Lower PPO activity reduced the fruiting body enzymatic browning rate through decreased expression of LdPpo1, LdPpo2, and LdPpo3 during storage at 4 °C for 16 days. This activity may be used to determine the effectiveness of ultrasonication.     

Effect of ultrasound and chlorine dioxide on Salmonella Typhimurium and Escherichia coli inactivation in poultry chiller tank water

This study evaluated the application of ultrasound alone or combined with chlorine dioxide (ClO₂) for Salmonella Typhimurium and Escherichia coli inactivation in poultry processing chiller tank water. A Full Factorial Design (FFD) 2² was conducted for each microorganism to evaluate the effect of ultrasound exposure time (x₁: 1 to 9 min; fixed: 37 kHz; 330 W; 25 °C) using a bath, and ClO₂ concentration (x₂: 1 to 17 mg L⁻¹) on microorganism count expressed in log CFU mL⁻¹ in distilled water. Variable x₂ had a negative effect on Salmonella Typhimurium (-5.09) and Escherichia coli (-2.00) count, improving the inactivation; while a x₁ increase present no inactivation improvement, explaining the use of x₁ lower level (1 min) and x₂ higher level (17 mg L⁻¹). The best condition for microorganism inactivation based on FFD was evaluated in chiller tank water (with organic matter) at 25, 16, and 4 °C; x₁ was kept (1 min), however x₂ was adjusted to obtain the same residual free chlorine (2.38 mg L⁻¹) considering the ClO₂ consumption by organic matter, achieving the value of 30 mg L⁻¹. An inactivation of 49% and 31% were observed for Salmonella Typhimurium and Escherichia coli. When ultrasound was replaced by a simple agitation in the presence of ClO₂, there was no inactivation for both microorganisms. Moreover, at poultry carcass pre-chilling (16 °C) and chilling (4 °C) conditions, the synergism of ultrasound combined with ClO₂ was more pronounced, with microorganisms’ reductions up to 100%.     

Impact of high-intensity thermosonication treatment on spinach juice: Bioactive compounds,rheological, microbial,and enzymatic activities

To study the impacts of thermosonication (TS), the spinach juice treated with TS (200 W, 400 W, and 600 W, 30 kHz, at 60 ± 1 °C for 20 mint) were investigated for bioactive compounds, antioxidant activities, color properties, particle size, rheological behavior, suspension stability, enzymatic and microbial loads. As a result, TS processing significantly improved the bioactive compounds (total flavonols, total flavonoids, total phenolic, carotenoids, chlorophyll, and anthocyanins), antioxidant activities (DPPH and FRAP assay) in spinach juice. Also, TS treatments had higher b*, L*, hue angle (h⁰), and chroma (C) values, while minimum a* value as compared to untreated and pasteurized samples. TS processing significantly reduced the particle size, improved the suspension stability and rheological properties (shear stress, apparent viscosity, and shear rate) of spinach juice as compared to the untreated and pasteurized sample. TS plays a synergistic part in microbial reduction and gained maximum microbial safety. Moreover, TS treatments inactivated the polyphenol oxidase and peroxidase from 0.97 and 0.034 Abs min⁻¹ (untreated) to 0.31 and 0.018 Abs min⁻¹, respectively. The spinach juice sample treated at a high intensity (600 W, 30 kHz, at 60 ± 1 °C for 20 mint, TS3) exhibited complete inactivation of microbial loads (<1 log CFU/ml), the highest reduction in enzymatic activities, better suspension stability, color properties, and highest bioactive compounds. Collectively, the verdicts proposed that TS processing could be a worthwhile option to pasteurize the spinach juice to enhance the overall quality.     

Combined effect of ultrasound,heat, and pressure on Escherichia coli O157:H7, polyphenol oxidase activity,and anthocyanins in blueberry (Vaccinium corymbosum) juice

The objective of this study was to evaluate the effect of different treatments—heat treatment (HT), sonication (SC), thermosonication (TS), manosonication (MS), manothermal (MT), and manothermosonication (MTS) on Escherichia coli O157:H7, polyphenol oxidase (PPO), and anthocyanin content in blueberry juice. First, samples were treated at different temperatures (30, 40, 50, 60, 70, and 80 °C) and power intensities (280, 420, 560, and 700 W) for 10 min. Subsequently, samples were treated using combinations of power intensity and mild temperature for 10 min. For further study, samples were treated using HT (80 °C), TS (40 °C, 560 W), MT (350 MPa, 40 °C), MS (560 W, 5 min/350 MPa), or MTS (560 W, 5 min, 40 °C/350 MPa, 40 °C) for 5, 10, 15, 20 min for each treatment, and the results compared between treatments. HT significantly reduced PPO activation (2.05% residual activity after only 5 min), and resulted in a 2.00-log reduction in E. coli O157:H7 and an 85.25% retention of anthocyanin. Escherichia coli O157:H7 was slightly inactivated by TS after 5 min (0.17-log reduction), while residual PPO activity was 23.36% and anthocyanin retention was 98.48%. However, Escherichia coli O157:H7 was rapidly inactivated by MTS (5.85-log reduction) after 5 min, while anthocyanin retention was 97.49% and residual PPO activity dropped to 10.91%. The destruction of E. coli cells as a result of these treatments were confirmed using SEM and TEM. Therefore, a combination of sonication, high pressure, and mild heat allows the safety of blueberry juice to be maintained without compromising the retention of desirable antioxidant compounds.     

Shelf life,physicochemical, microbiological and antioxidant properties of purple cactus pear (Opuntia ficus indica) juice after thermoultrasound treatment

The objective of this study was to evaluate changes in color, betalain content, browning index, viscosity, physical stability, microbiological growth, antioxidant content and antioxidant activity of purple cactus pear juice during storage after thermoultrasonication at 80% amplitude level for 15 and 25 min in comparison with pasteurized juice. Thermoultrasound treatment for 25 min increased color stability and viscosity compared to treatment for 15 min (6.83 and 6.72 MPa, respectively), but this last parameter was significantly lower (p < 0.05) compared to the control and pasteurized juices (22.47 and 26.32 MPa, respectively). Experimental treatment reduced significantly (p < 0.05) sediment solids in juices. Total plate counts decreased from the first day of storage exhibiting values of 1.38 and 1.43 log CFU/mL, for 15 and 25 min treatment, respectively. Compared to the control, both treatments reduced enterobacteria counts (1.54 log CFU/mL), and compared to pasteurized juice decreased pectinmethylesterase activity (3.76 and 3.82 UPE/mL), maintained high values of ascorbic acid (252.05 and 257.18 mg AA/L) and antioxidant activity (by ABTS: 124.8 and 115.6 mg VCEAC/100 mL; and DPPH: 3114.2 and 2757.1 μmol TE/L). During storage thermoultrasonicated juices had a minimum increase in pectinmethylesterase activity (from day 14), and exhibited similar total plate counts to pasteurized juice. An increase of phenolic content was observed after 14 days of storage, particularly for treatment at 80%, 25 min, and an increase in antioxidant activity (ABTS, DPPH) by the end of storage.     

Effect of ultrasound processing on anthocyanins and color of red grape juice

Grape juice samples were sonicated with processing variables of amplitude level (24.4–61.0 μm) and treatment time (0–10 min) at a constant frequency of 20 kHz and pulse durations of 5 s on and 5 s off. A full factorial experimental design with regression modeling was employed to investigate the main effects of amplitude level and treatment time on anthocyanins and color parameters. Significant effects of sonication on major anthocyanins cyanidin-3-O-glucosides (CA), malvanidin-3-O-glucosides (MA) and delphinidin-3-O-glucosides (DA), color values (L*, a*, b*) and color index (CI) were observed. Prediction models were found to be significant (p < 0.05) with low standard errors and high coefficients of determination (R²). Model predictions for critical quality parameters of anthocyanins (CA; MA; DA), color values (L*, a*, b*), TCD and CI inactivation were closely correlated to the experimental results obtained. Significant retention of anthocyanin content in grape juice was observed for CA (97.5 %); MA (48.2 %) and DA (80.9%) during sonication. CI and other color combinations (L*a*b*, L*a*/b* and L*b*/a*) were found to be strongly correlated with anthocyanin content. This study shows that sonication could be employed for as a preservation technique for fruit juice processing where anthocyanin retention is desired.     

Effect of combined ultrasonic and enzymatic extraction technique on the quality of noni (Morinda citrifolia L.) juice

In order to obtain noni juice with high yield and good quality, the effect of combined extraction technique of enzymatic treatment (EZ) and ultrasonication (US) on the overall quality of noni juice was investigated. Moreover, the extraction performance of the EZ-US combined extraction technique was compared with that of EZ-based extraction and the US-based extraction. Response surface methodology (RSM) was designed to optimize the parameters of ultrasonic treatment, by taking consideration of the extraction efficiency, quality parameters and bioactive ingredients of noni juice. The results indicated that combined ultrasonic and enzymatic treatment achieved a synergistic effect on promoting the quality of noni juice. The maximum juice yield of 67.95 % was obtained under ultrasonication for 10 min at 600 W after enzymatic treatment (EZU). In addition, EZU-treated juice exhibited the highest contents of total phenolic and flavonoid, which were 148.19 ± 2.53 mg gallic acid/100 mL and 47.19 ± 1.22 mg rutin/100 mL, respectively, thus contributing to better antioxidant activity. Moreover, the EZU treatment significantly reduced the particle size of noni juice, and improved its suspension stability and rheological properties. FTIR results indicated that the treatments did not bring major changes in the chemical structure and the functional groups of compounds in noni juice. Therefore, EZU treatment can be successfully applied to the extraction of noni juice with better nutritional properties and overall quality.     

Enzymatic inactivation and antioxidant properties of blackberry juice after thermoultrasound: Optimization using response surface methodology

The purpose of this research was to optimize the thermoultrasound conditions for blackberry juice using the response surface methodology and considering juice quality parameters and antioxidant capacity. With the exception of microbial growth, the response variables showed high correlation coefficients with the mathematical model (R²adj > 0.91). Thermoultrasound treatment inactivated all the evaluated microorganisms, and at the optimum conditions (50 ± 1 °C at 17 ± 1 min) it increased enzyme inactivation and antioxidant activity in comparison to pasteurized juice. The results demonstrated that thermoultrasound can be an alternative to pasteurization for the production of safe and high-quality juices with the added value of higher concentration of bioactive compounds and antioxidant capacity.     

Ultrasonic-assisted extraction and automated determination of catalase and lipase activities in bovine and poultry livers using a digital movie-based flow-batch analyzer

An ultrasonic reactor (UR) was developed and coupled to a digital movie-based flow-batch analyzer (DM-FBA) for the ultrasonic-assisted extraction (UAE) and fast determination of catalase and lipase activities in bovine and poultry livers. The lab-made UR mainly consisted of a borosilicate glass container and a piezoelectric disc. The DM-FBA mainly consisted of a webcam, an ultrasonic actuator controller, a peristaltic pump, six solenoid valves, a valve driver, a mixing chamber, a magnetic stirrer, an Arduino Mega 2560, and a personal computer. This setup, named UR-DM-FBA, was controlled by custom software. Ultrasound (US) frequency, US power, sonication time, and concentration of extraction agent were optimized using the Taguchi method. Experiments at silent conditions (mechanical stirring at 1500 rpm) were carried out to evaluate extraction efficiency. Optimized parameters for the UAE of catalase were US frequency of 30 kHz, 2.0 mL of Triton X-100, sonication time of 270 s, and US power of 10.8 W. For the UAE of lipase, the optimized parameters were US frequency of 20 kHz, 0.30 mL of triethanolamine, sonication time of 270 s, and US power of 18 W. Catalase and lipase activities obtained with the UR were, on average, 1.9 × 10³% and 2.0 × 10³% higher than those obtained at silent conditions, respectively, which indicates that that the lab-made UR was capable of extracting these enzymes more efficiently. Determinations using the UR-DM-FBA were highly accurate (relative error ranging from −1.98% to 1.96% for bovine catalase, −0.65% to 0.76% for bovine lipase, −2.03 to 2.08% for poultry catalase, and −0.55% to 0.64% for poultry lipase) and precise (overall coefficient of variation <0.02% for bovine and poultry catalase and <0.2% for bovine and poultry lipase). Results obtained with the proposed system and reference methods were in good agreement according to the paired t-test (95% confidence level). High sampling rates (>69 h⁻¹) and low sample/reagent consumption (<1.6 mL) were also obtained. Due to the highly efficient UAE, the proposed system can be applied for fast and accurate quantification of lipase and catalase in biological samples with low waste generation.     

Ultrasound assisted modulation of yeast growth and inactivation kinetics

The yeast Saccharomyces cerevisiae is well known for its application in the food industry for the purpose of developing fermented food. The ultrasound (US) technology offer a wide range of applications for the food industry, including the enhancement of fermentation rates and inactivation of microbial cells. However, a better understanding and standardization of this technology is still required to ensure the scaling-up process. This study investigated the effect of the US technology on the growth of S. cerevisiae using frequencies of 20, 25, 45 and 130 kHz, treatment periods from 2 to 30 min. Furthermore, yeast kinetics subjected to US treatments were evaluated using modelling tools and scanning electron microscopy (SEM) analysis to explore the impact of sonication on yeast cells. Yeast growth was monitored after different US treatments plotting optical density (OD) at 660 nm for 24 h at 30 ⁰C. Growth curves were fitted using models of modified Gompertz and Scale-Free which showed good parameters of the fit. In particular, US frequencies of 45 and 130 kHz did not have a disruptive effect in lag phase and growth rate of the yeast populations, unlike the frequency of 20 kHz. Moreover, inactivation curves of yeast cells obtained after exposure to 20 and 25 kHz also observed the best fit using the Weibull model. US frequency of 20 kHz achieved significant reductions of 1.3 log cfu/mL in yeast concentration and also induced important cell damage on the external structures of S. cerevisiae. In conclusion, the present study demonstrated the significant effect of applying different US frequencies on the yeast growth for potential application in the food industry.