High-Pressure and Temperature Effects on Enzyme Inactivation in Tomato Puree

Application and Effects of Ohmic-Vacuum Combination Heating on the Quality Factors of Tomato Paste

Ohmic-vacuum combination heating is a common method used in the food industry as a concentration process. In the present study, an OH-VC combination heating system was developed for producing tomato paste at temperatures of 70, 80, and 90 °C and pressure of 0.3, 0.5, and 0.7 bar and electric field of 1.82, 2.73, and 3.64 V/cm using a central composite design. The effects of heating conditions on the quality and sensory evaluation of tomato paste were also evaluated. Each combination of temperature, pressure, and the electric field was quantified for specific energy consumption, energy efficiency, and productivity. A decrease of 35.08% in the amount of acid ascorbic and lycopene content 19.01%, using conventional heating compared to ohmic-vacuum heating under optimized conditions, was attained. The results also highlighted an increase in the amount of HMF (69.79%) and PME (24.33%) using conventional heating compared to ohmic-vacuum heating under optimized conditions. Ascorbic acid, lycopene, titratable acidity, productivity, energy efficiency was higher than conventional heating; on the other hand, HMF, PME, pH, SEC were lower than conventional heating at the applied OH-VC process. No significant effects between OH-VC and conventional heating on the TSS were observed. In addition, OH-VC heating was highly efficient in the inhibition of bacterial growth. Further, a minor effect on the sensory properties of tomato paste with OH-VC heating compared to the conventional treatment. The obtained results indicate a strong potential for an OH-VC combination heating system as a rapid-heating, high-efficiency alternative for saving electrical energy consumption and preserving nutritional value.

Coir, an Alternative to Peat—Effects on Plant Growth, Phytochemical Accumulation, and Antioxidant Power of Spinach

The effects of four commercial substrates, a peat-based substrate, and three coir types (coir pith, coir chips, and coir pith + fibers) on yield, phytochemical accumulation, and antioxidant activity were evaluated in Spinacia oleracea L. cv. ‘Manatee’. Soil-blocked spinach seedlings were transplanted into Styrofoam planting boxes filled with the substrate. Each planting box was irrigated daily by drip with a complete nutrient solution, and the irrigation scheduling was optimized to the peat. Leaf area and fresh yield in coir pith and coir pith + fiber were similar to those obtained in peat. However, shoot dry weight accumulation and leaf chlorophyll were lower in plants grown in coir. Substrate type did not affect leaf carotenoids. Total flavonoid content was higher in plants grown in the different types of coir. Total phenols and antioxidant activity (DPPH) were higher in plants grown in coir pith. This indicates that the different coir types, mainly coir pith, may provide an alternative to peat since they allowed a high fresh yield to be reached and the total flavonoids to be increased. In contrast, the levels of other phytochemicals and antioxidant activity were usual for spinach. However, further research is necessary to analyze the effects of irrigation scheduling and the nutrient solution adjusted to each growing medium on yield and phytochemical accumulation.

Quality Parameters of Juice Obtained from Hydroponically Grown Tomato Processed with High Hydrostatic Pressure or Heat Pasteurization

The effect of processing such as high hydrostatic pressure (HHP) (400-600 MPa/15 min) or low pasteurization temperature (LPT) (74°C/2 min) or high pasteurization temperature (HPT) (90°C/1 min) on selected quality parameters of juice obtained from hydroponically cultivated beef tomatoes was investigated. The total polyphenols content (TPC), total phenolic index (TPI), Trolox equivalent antioxidant capacity (ABTS) and ferric reducing antioxidant power (FRAP) were analysed in the fresh and processed juices stored for 0, 7 and 14 days. What is more, colour parameters (L^∗, a^∗, b^∗, ∆E), the activity of polyphenol oxidase (PPO) and peroxidase (POD) and microbial stability were also analyzed following the juices storage. Among all the tested samples, the juice exposed to 600 MPa for 15 min showed superior quality. Samples treated with 600 MPa for 15 min and stored for 0, 7 and 14 days had high TPC, TPI, ABTS, FRAP and a^∗ values. As demonstrated, these tested samples at the end of the storage period retained 90% and 95% of their polyphenol content and antioxidant capacity, respectively. As in the case of pasteurization, juice processing at 600 MPa for 15 min clearly reduced the activity of food-spoiling enzymes (PPO, POD) as well as the microbial count. The obtained results showed that TPC was significantly and positively correlated with TPI, ABTS and FRAP parameters.

Chimeric Phage Nanoparticles for Rapid Characterization of Bacterial Pathogens: Detection in Complex Biological Samples and Determination of Antibiotic Sensitivity

Rapid, specific, and sensitive detection of pathogenic bacteria in drink, food, and clinical samples is an important goal for public health. In addition, rapid characterization of antibiotic susceptibility could inform clinical choices and improve antibiotic stewardship. We previously reported a straightforward, inexpensive strategy to detect Gram-negative bacterial pathogens, including Pseudomonas aeruginosa, Vibrio cholerae, and Escherichia coli, taking advantage of the high affinity and specificity of phages for their bacterial hosts. Chimeric phages targeted different bacterial pathogens, and thiolation of the phages induced aggregation of gold nanoparticles (AuNPs), leading to a visible colorimetric response in the presence of at least ∼100 cells of the target bacteria. Here, we apply this strategy to complex biological samples (milk, urine, and swabs from a porcine ex vivo model of P. aeruginosa infection). We also show that this assay can be used to identify the antibiotic susceptibility profile based on detection of bacterial growth in the presence of different antibiotics. The prospect for using phage-conjugated AuNPs to detect bacterial pathogens in clinical samples and guide antibiotic choice is discussed.

Comparison of pulsed vacuum and ultrasound osmotic dehydration on drying of Chinese ginger (Zingiber officinale Roscoe): Drying characteristics, antioxidant capacity, and volatile profiles

The effects of pulsed vacuum osmotic dehydration (PVOD) and ultrasound osmotic dehydration (USOD) on drying characteristics and quality attributes of ginger were investigated. PVOD was subjected to pulsed vacuum at 13 kPa for 30 min, and USOD was subjected to ultrasound with the frequency of 40 kHz for 30 min. After PVOD and USOD treatments, the samples were then dried at intermittent microwave & air-drying oven with an output of 700 W and temperature of 60°C to the final moisture content of 0.12 g water/g d.w. The results showed PVOD and USOD treatments could improve the total phenolic contents by -1.8% to 16.4%, total flavonoid content by 7.7%-18.7%, DPPH radical scavenging by 9.5%-12.2%, and ABTS+ antioxidant activity by 17.8%-27.4%, although they prolonged the later stages drying of ginger. Besides, the PVOD- and USOD-pretreated dried samples had less brownings than the untreated-dried samples which could be attributed to the inactivation of polyphenol oxidase (PPO) and peroxidase (POD). The PPO activity was significantly reduced in the PVOD and USOD ginger, whereas POD activity was decreased in USOD ginger but increased in PVOD ginger. Moreover, PVOD pretreatment also led to a better preservation of volatile profiles and cell structure than USOD treatment. Therefore, both PVOD and USOD are effective pretreatments for drying of ginger.

Determination of urea in milk based on N -bromosuccinimide–dichlorofluorescein postchemiluminescence method

A new postchemiluminescence (PCL) reaction was observed when urea was injected into the reaction mixture after the CL reaction of N-bromosuccinimide and dichlorofluorescein. A possible reaction mechanism was proposed based on the studies of the CL kinetic characteristics, CL spectra, fluorescence spectra, and other experiments. A new flow injection CL method for the determination of urea was established based on the PCL reaction. The relative standard deviation for the determination of urea was 1.3% (n = 11, c = 5.0 × 10⁻⁸ g/mL). The CL intensity responded linearly to the concentration of urea in the range 2.0 × 10⁻⁹–1.0 × 10⁻⁶ g/mL (r = 0.9992). The detection limit was 7 × 10⁻¹⁰ g/mL. The method had been applied to the determination of urea in milk with satisfactory results.

Effects of high hydrostatic pressure processing and of glucose oxidase-catalase addition on the color stability and sensorial score of grape juice / Efectos del tratamiento con altas presiones y de la adición de glucosa oxidasa-catalasa en la estabilidad del color y en la evaluación sensorial del zumo de uva

The effects of high hydrostatic pressure treatment (HHP) and the use of glucose oxidase-catalase enzymes on the color stability of a white grape juice were studied. The cold-prepared grape juice was stored for three weeks at 5 °C and evaluated for color and non-flavonoid phenolic content. The HHP treatments at 600 and 900 MPa slowed the degradation of non-flavonoid phenolics and reduced the rate of the browning during storage. No significant effect on the color was observed using 300 MPa. Further color stabilization was obtained using glucose oxidase-catalase enzymes and by setting the initial temperature of water inside the pressure vessel at 50 °C prior to HHP treatment. The sensory analyses indicated that enzymes and HHP improved the aroma and taste of juices; by contrast, oper ating the HHP process at an initial temperature of 50 °C showed no significant effect.

Enzymatic protein hydrolysates from high pressure-pretreated isolated pea proteins have better antioxidant properties than similar hydrolysates produced from heat pretreatment

Isolated pea protein (IPP) dispersions (1%, w/v) were pretreated with high pressure (HP) of 200, 400, or 600 MPa for 5 min at 24 °C or high temperature (HT) for 30 min at 100 °C prior to hydrolysis with 1% (w/w) Alcalase. HP pretreatment of IPP at 400 and 600 MPa levels led to significantly (P<0.05) improved (>40%) oxygen radical absorption capacity (ORAC) of hydrolysates. 2,2-Diphenyl-1-picrylhydrazyl, superoxide radical and hydroxyl radical scavenging activities of pea protein hydrolysates were also significantly (P<0.05) improved (25%, 20%, and 40%, respectively) by HP pretreatment of IPP. Protein hydrolysates from HT IPP showed no ORAC, superoxide or hydroxyl scavenging activity but had significantly (P<0.05) improved (80%) ferric reducing antioxidant power. The protein hydrolysates had weaker antioxidant properties than glutathione but overall, the HP pretreatment was superior to HT pretreatment in facilitating enzymatic release of antioxidant peptides from IPP.

Combined effect of high hydrostatic pressure and mild heat treatments on pectin methylesterase (PME) inactivation in comminuted orange

BACKGROUND

Comminuted orange, a product obtained by grinding the juice and peel and used to formulate beverages, has a high pectin methylesterase (PME) activity; thus the inactivation of this enzyme is necessary to avoid quality losses related to cloud loss. The use of high hydrostatic pressure (HHP) and mild temperature allows inactivation of enzymes with minimal quality changes. This work aimed to evaluate the effect of pressure, mild temperature and time of treatment, including come-up and holding time, on the inactivation of PME in comminuted orange, and to apply kinetic and response surface models (RSM) to predict residual PME activity (A/A0 ).

RESULTS

During come-up time in treatments at 68 °C, the higher the pressure, the lower was the A/A0 obtained. At 550 MPa/68 °C/10 min the lowest residual activity value was obtained (15.6%). A/A0 was well adjusted to the RSM, and a first-order kinetic model was applied to describe the inactivation of PME. In general, the higher the pressure, the lower was the A/A0 reached, as the increasing values of k from 3.5 × 10(-2) to 55.5 × 10(-2) min(-1) indicated. Activation volume (Va ) values ranging from -9.2 to -17.7 cm(3) mol(-1) , and activation energies (Ea ) between 50.0 and 68.2 kJ mol(-1) were calculated.

CONCLUSION

550 MPa/68 °C/10 min, 350 MPa/68 °C/10 min and 450 MPa/56 °C/10 min treatments were satisfactory (∼84% inactivation) to inactivate PME. A first-order kinetic model was applied to describe PME inactivation, and the resulting A/A0 adjusted to the RSM. In addition, linearized Arrhenius and Eyring equations were well fitted in order to obtain Ea and Va , respectively.

Effect of high hydrostatic pressure on overall quality parameters of watermelon juice

High hydrostatic pressure as a kind of non-thermal processing might maintain the quality of thermo-sensitive watermelon juice. So, the effect of high hydrostatic pressure treatment on enzymes and quality of watermelon juice was investigated. After high hydrostatic pressure treatment, the activities of polyphenol oxidase, peroxidase, and pectin methylesterase of juice decreased significantly with the pressure ( P < 0.05). Inactivation of polyphenol oxidase and peroxidase could be fitted by two-fraction model and that of pectin methylesterase could be described by first-order reaction model. Titratable acidity, pH, and total soluble solid of juice did not change significantly ( P > 0.05). No significant difference was observed in lycopene and total phenolics after high hydrostatic pressure treatment when compared to the control ( P > 0.05). Cloudiness and viscosity increased with pressure ( P < 0.05) but did not change significantly with treatment time ( P > 0.05). a*- and b*-value both unchanged after high hydrostatic pressure treatment ( P > 0.05) while L*-value increased but the values had no significant difference among treated juices. Browning degree after high hydrostatic pressure treatment decreased with increase in pressure and treatment time ( P < 0.05). Through the comparison of total color difference values, high hydrostatic pressure had little effect on color of juice. The results of this study demonstrated the efficacy of high hydrostatic pressure in inactivating enzymes and maintaining the quality of watermelon juice.

Pepsin immobilized on high-strength hybrid particles for continuous flow online digestion at 10,000 psi

Pepsin was immobilized on ethyl-bridged hybrid (BEH) particles, and digestion performance was evaluated in a completely online format, with the specific intent of using the particles for hydrogen-deuterium exchange mass spectrometry (HDX MS) experiments. Because the BEH particles are mechanically strong, they could withstand prolonged, continuous high-pressure at 10,000 psi. Online digestion was performed under isobaric conditions with continuous solvent flow, in contrast to other approaches where the pressure or flow is cycled. As expected, digestion efficiency at 10,000 psi was increased and reproducibly produced more peptic peptides versus digestion at 1000 psi. Prototype columns made with the BEH pepsin particles exhibited robust performance, and deuterium back-exchange was similar to that of other immobilized pepsin particles. These particles can be easily incorporated in existing HDX MS workflows to provide more peptide coverage in experiments where fast, efficient, and reproducible online pepsin digestion is desired.

Effect of ultrahigh hydrostatic pressure on the activity and structure of mushroom (Agaricus bisporus) polyphenoloxidase

High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.

Effects of high hydrostatic pressure on enzymes, phenolic compounds, anthocyanins, polymeric color and color of strawberry pulps

BACKGROUND

Changes in activity of polyphenol oxidase (PPO), peroxidase (POD) and β-glucosidase, individual phenolic compounds other than anthocyanins, total phenols, monomeric anthocyanins, polymeric color and instrumental color of strawberry pulps were assessed after high hydrostatic pressure (HHP) (400-600 MPa 5-25 min(-1)) at room temperature.

RESULTS

β-Glucosidase was activated by 4.7-16.6% at 400 MPa 5-25 min(-1) and inactivated by 8.0-41.4% at 500 or 600 MPa. PPO and POD were inactivated at all pressures, the largest reduction in activity being 41.4%, 51.5% and 74.6%, respectively. The individual phenolic compounds and total phenols decreased at 400 MPa, but total phenols increased at 500 or 600 MPa. However, the monomeric anthocyanins, polymeric color and redness (a*) exhibited no change. HHP induced a decrease in lightness (L*) and an increase in yellowness (b*) at 400 MPa, but no significant alteration in L* value and b* value at 500 or 600 MPa was observed; this was attributed to higher residual activity of PPO, POD and β-glucosidase at 400 MPa. Total color difference (ΔE) was ≥5 at 400 MPa and ≤3 at 500 or 600 MPa.

CONCLUSION

HHP effectively retained anthocyanins, phenolic compounds and color of strawberry pulps, and partly inactivated enzymes.

Self-nanoemulsifying drug delivery systems: formulation insights, applications and advances

There has been a resurgence of interest in nanoemulsions for various pharmaceutical applications since low-energy emulsification methods, such as spontaneous or self-nanoemulsification, have been described. Self-nanoemulsifying drug delivery systems (SNEDDS) are anhydrous homogenous liquid mixtures consisting of oil, surfactant, drug and coemulsifier or solubilizer, which spontaneously form oil-in-water nanoemulsion of approximately 200 nm or less in size upon dilution with water under gentle stirring. The physicochemical properties, drug solubilization capacity and physiological fate considerably govern the selection of the SNEDDS components. The composition of the SNEDDS can be optimized with the help of phase diagrams, whereas statistical experimental design can be used to further optimize SNEDDS. SNEDDS can improve oral bioavailability of hydrophobic drugs by several mechanisms. The conversion of liquid SNEDDS to solid oral dosage forms or solid SNEDDS has also been achieved by researchers. Solid SNEDDS can offer better patient compliance and minimize problems associated with capsules filled with liquid SNEDDS.

Combined enzymatic and high-pressure processing affect cell wall polysaccharides in berries

The effect of high-pressure processing (HPP) on cell wall polysaccharides in berries was investigated. HPP decreased the degree of methyl esterification (DM), probably by activation of pectin methyl esterase (PME), and improved the extractability of pectins. When commercial enzyme mixtures were added to mashed berries, a synergistic effect was observed between treatment with commercial enzymes and HPP. Compared to treatment at atmospheric pressure, pectic polysaccharides were degraded to a larger extent when HPP was used. In contrast, hemicelluloses were hardly affected by the added enzymes when HPP was included, although they were degraded during similar treatment at atmospheric pressure. Additionally, the activity of rhamnose-releasing enzymes present in minor quantities might be enhanced after HPP, resulting in a decrease of rhamnose in the polymeric cell wall material. These results exploring the effect of HPP at representative conditions clearly point out the potential of HPP for polysaccharide modification.