Steady- and Unsteady-State Determination of the Water Vapor Permeance (<Emphasis Type="Italic">WVP</Emphasis>) of Polyethylene Film to Estimate the Moisture Gain of Packed Dry Mango

The water vapor permeance (WVP; g m^?2 d^?1 Pa^?1) of packaging films quantifying the water vapor transfer rate between foods and its surroundings is usually determined in units operating under steady-state conditions that do not necessarily reflect food handling scenarios. This study evaluated the determination of the WVP of a polyethylene (PE) film by steady-state method ASTM F1249-06 using a permeability cell and unsteady-state method ASTM E96/E96M in which 102 vacuum-sealed PE bags containing silica gel were stored (37.8 °C, 75% relative humidity) and weighed over 25 days. Average steady-state WVP (2.935 ± 0.365 × 10^?3, n = 4) fell within the 95% quantiles of unsteady-state WVP values (1.818–3.183 × 10^?3, n = 2142). Moisture uptake of dehydrated mango stored at 37.8 °C and 75% relative humidity was predicted with WVP values obtained by both methods. Predictions were validated by monitoring over 25 days the weight gain of 100 PE bags with dry mango. Experimental moisture averages during storage fell within one standard deviation of predictions using the unsteady-state WVP (R ² = 0.974). The same was observed only until day 15 for predictions obtained with the steady-state WVP. Calculations for days 20–25 overestimated the moisture uptake by 6.0–7.2%, resulting in registered R ² = 0.924. The unsteady-state WVP determination is low-cost, uses large numbers of film samples, and allowed more accurate predictions of dry mango moisture uptake. Knowledge of the moisture uptake controlled by the film WVP is essential when predicting the safety and quality changes limiting the shelf-life of foods.     

Changes in Quality Attributes During Storage of High-Pressure and Thermally Processed Pineapple Puree

The primary issue of the pineapple puree processing industry is its limited stability. The study compares the quality changes in high-pressure and thermally processed pineapple puree at different storage conditions and estimates the shelf-life. The untreated (S1) and treated samples (S2, S3, and S4 treated at 600 MPa/50 °C/13 min, 600 MPa/70 °C/20 min, and 0.1 MPa/95 °C/12 min, respectively) packed in ethylene vinyl alcohol (EVOH) and multi-layered (ML) polyethylene terephthalate (PET) pouches were stored up to 125 days at 5, 15, and 25 °C. The total color change (?E*) and browning index during storage increased according to zero-order kinetic model, whereas ascorbic acid (AA), total phenolics, and total antioxidant capacity followed the first-order decay. The overall sensory acceptability (OA) of S2 was higher than both S3 and S4 at 5 °C, and it dropped rapidly at 15 and 25 °C. The activity of polyphenol oxidase and pectin methylesterase in S3 and S4 was less than 10 % up to 120 days at 5 °C. The consistency (κ) and residual enzyme activity in S2 decreased with storage duration and temperatures. For estimating the shelf-life, the change in OA was crucial for S2 and S3, whereas retention of AA served as the critical parameter for S4. The sample S2 packed in ML pouch was found to be the best sample having the shelf-life (microbial count?<?6-Log cfu g^?1, ?E*?<?12, OA?>?5, and AA?>?200 mg kg^?1) of 120, 50, and 25 days at 5, 15, and 25 °C, respectively.     

Prediction of shelf-life and changes in the quality characteristics of semidried persimmons stored at different temperatures

This study was performed to investigate changes in the quality characteristics and shelf-life of semidried persimmons stored at different temperatures using acceleration experiments. In order to estimate quality changes in the samples, we evaluated the physicochemical properties, microbiological changes, and sensory features of the samples periodically after storage at ?20, ?10, 0, and 10 °C. At all storage temperatures, CIE L ^* a ^* b ^* values decreased significantly. Based on the results of this study, regression equations are set up. L ^* had the highest correlation and were therefore used to determine quality factor. The activation energy, which was calculated using the Arrhenius equation, was found to be 12.98 kcal/mol, and the Q10-values were 3.81, 2.07, and 2.06 at ?20 to ?10 °C, ?10 to 0 °C, and 0 to 10 °C, respectively. Therefore, the expected expiration dates of the semidried persimmons were estimated to be 203.83, 53.46, 22.00, and 8.71 days at ?20, ?10, 0, and 10 °C.     

Quality Changes in Mango Juice Treated by High-Intensity Pulsed Electric Fields Throughout the Storage

The effect of high-intensity pulsed electric fields (HIPEF) processes on Listeria innocua inhibition, physicochemical parameters and activity of oxidative enzymes of mango juice was evaluated to set the optimal HIPEF treatment time. Quality parameters, microbial population and bioactive compounds of HIPEF-treated (35 kV/cm, 1800 μs) and thermally treated (TT) (90 °C, 60 s) mango juices were studied and compared with those non-treated during 75 days of storage at 4 °C. HIPEF treatment for 800 μs ensured 5 log reductions of L. innocua. Polyphenoloxidase (PPO), lipoxygenase (LOX) and peroxidase (POD) residual activities were significantly reduced to 70, 53 and 44%, respectively, at treatment times of 1800 μs. Similar sensory properties compared with fresh mango juice were attained from product treated at 1800 μs. Moreover, fresh mango juice colour (L* = 38.79, h° = 106.57) was preserved after HIPEF treatment throughout storage. Moulds and yeasts and psychrophilic bacteria counts in HIPEF-treated (1800 μs) mango juice remained below 6 log cycles CFU/mL up to 2 months of refrigerated storage. The content of total phenolic compounds in those HIPEF-treated increased from 333 to 683 μg of GAE/mL from day 0 to the end of storage. Hence, the application of HIPEF may be a feasible treatment in order to ensure microbiological stability, high bioactive compound content and fresh-like characteristics of mango juice.     

Development and characterization of reconstituted hydrogel from <Emphasis Type="Italic">Aloe vera</Emphasis> (<Emphasis Type="Italic">Aloe barbadensis</Emphasis> Miller) powder

Structural and rheological characterization of reconstituted hydrogels developed from A. vera non-fibrous alcohol insoluble residue (NFAIR) powder using different methods [viz., shaking (S), heating-shaking (HS), and heating (H)] and concentrations (viz., 0.2–1.6 %, w/v) was carried out. Functional group distribution by FTIR spectroscopy and Congo red (CR) method revealed the presence of acetylated acemannan in A. vera powder. Dynamic oscillation studies of A. vera (NFAIR) fluids at all concentrations of 0.2–1.6 %, w/v, showed gel strength in the order of H > HS > S method. However, in H method, increase in concentration from 0.2 to 1.6 %, w/v showed the conformational transition from semi-diluted solution to weak gel nature. Rheological models described the effect of heating temperatures (HT); 30–90 °C, and times (Ht); 15–60 min on viscoelastic behavior in reconstituted A. vera fluids. The reconstituted A. vera hydrogel prepared with a concentration of 1.6 %, w/v using 50 °C (HT) and 30 min (Ht) condition showed a good agreement with the Power law (storage modulus, G′) and Weak gel model (complex modulus, G*) fitted data (R² > 0.94) resulting higher viscoelastic moduli intercepts; G′₀ (71.5 Pa s ^n′), G″₀ (33.5 Pa s ^n″), lower slopes; n′ (0.22), n″ (0.06), higher network strength (A _F , 121.3 Pa s^1/z ) and number of network (z, 5.3) values. The obtained results suggested that heating at 50 °C/30 min can develop aqueous weak gel networks of A. vera with enhanced gel strength which may be utilized as a novel gelling agent for wide variety of targeted applications in food and pharmaceutical sectors.     

Real-Time Monitoring of Organic Carrot (var. Romance) During Hot-Air Drying Using Near-Infrared Spectroscopy

The worldwide consumption of dried carrot (Daucus carota L.) is on a growing trend. Conventional methods for drying carrots include hot-water blanching followed by hot-air drying, which is usually uncontrolled and therefore prone to product quality deterioration. Thus, there is a need for innovative drying systems that yield high-value end products. In this study, the efficacy of NIR spectroscopy for the non-destructive monitoring of physicochemical changes and drying behaviour in organic carrot slices during 8-h hot-air drying at 40 °C was demonstrated using Partial least squares (PLS) regression and PLS discriminant analysis (PLS-DA). The impact of hot-water blanching pre-treatment (at 95 °C for 1.45 min) for enzyme inactivation on performances of both regression and classification models was also evaluated. PLS regression models were successfully developed to monitor changes in water activity (R ² = 0.91–0.96), moisture content (R ² = 0.97–0.98), total carotenoids content (R ² = 0.92–0.96), lightness for unblanched carrots (R ² = 0.80–0.83) and hue angle for blanched samples (R ² = 0.85–0.87). Soluble solids content prediction was poor for both treatments (RMSEP = 3.43–4.40). Classification models were developed to recognise dehydration phases of carrot slices on the basis of their NIR spectral profile using K-means and PLS-DA algorithms in sequence. The performance of each PLS-DA model was defined based on its accuracy, sensitivity and specificity rates. All of the selected models provided from good (> 0.85) to excellent (> 0.95) sensitivity and specificity for the predefined drying phases. Feature selection procedures yielded both regression and classification models with performances very similar to models computed from the full spectrum.     

A Cassava Starch–Chitosan Edible Coating Enriched with <Emphasis Type="Italic">Lippia sidoides</Emphasis> Cham. Essential Oil and Pomegranate Peel Extract for Preservation of Italian Tomatoes (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.) Stored at Room Temperature

The effect of edible cassava starch–chitosan coatings incorporated with rosemary pepper (Lippia sidoides Cham.) essential oil and pomegranate peel extract on the shelf-life of tomatoes during storage at 25 °C for 12 days was investigated. Sixteen formulations, containing 10 g L^?1 cassava starch and various concentrations of chitosan (5, 10, 20, 30 g L^?1), essential oil (0, 2.5, 5, 10 mL L^?1) and pomegranate peel extract (0, 5, 10, 20 mL L^?1) were prepared and applied to tomatoes. Physical–chemical and microbiological analyses were performed on days 1, 4, 8 and 12. Most of the coatings delayed the ripening of tomatoes, lowering the total soluble solids (38?44 g sucrose kg^?1) and weight loss (93?128 g kg^?1) and maintaining constant firmness compared to the uncoated tomatoes (45 g sucrose kg^?1, 175 g kg^?1) at 12 days of storage. Conversely, except red intensity (a*), which was higher for the uncoated samples, the colour parameters (L*, b*) of the coated and control tomatoes were similar at the end of storage. Uncoated and coated tomatoes showed no contamination during storage. The coatings showed potential to maintain the quality of tomatoes during storage at 25 °C for 12 days. In this context, tomatoes coated with the formulation comprising 10 g L^?1 cassava starch, 10 g L^?1 chitosan, 10 mL L^?1 essential oil and 20 mL L^?1 pomegranate peel extract showed the lowest weight loss and reduced total soluble solids content compared with uncoated ones.     

Effect of Microwave and High-Pressure Processing on Quality of an Innovative Broccoli Hummus

Two innovative broccoli (53% either cv. Parthenon or Bimi) hummuses were formulated. Semi-continuous microwave treatment (MW; 9 kW/40 s) or high-pressure processing (HPP; 550 MPa/10 min/23 °C) were applied to study hummus quality (microbiological/ physicochemical/sensory/bioactive compounds) during 28 days (5 °C). The initial mesophilic, psychrophilic, and Enterobacteriaceae loads of Parthenon/Bimi broccoli hummuses (2.8/3.2, 3.0/3.7, and 2.6/2.9 log CFU g^?1, respectively) were decreased by 1.6/1.9, 0.5/0.9, and 1.1/1.3 log units after HPP and in a lower degree by MW. In general, MW Parthenon hummus showed better sensory scores after 28 days, while HPP was better for Bimi. Higher (110%) glucoraphanin was observed in HPP Parthenon hummus, although MW better preserved sulforaphane. Treatments kept high phenolic levels during storage, being better preserved by HPP, with also higher total antioxidant capacity. Conclusively, MW and HHP treatments allowed to obtain a broccoli hummus with an excellent quality up to 28 days (5 °C) with also excellent bioactive quality.     

Modeling the Inactivation of <Emphasis Type="Italic">Listeria innocua</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> in Fresh-Cut Tomato Treated with Pulsed Light

The effectiveness of pulsed light (PL) treatments to inhibit microorganisms on fresh-cut tomatoes (Lycopersicon esculentum Mill., cv. Daniela) was investigated. Tomato slices inoculated with Escherichia coli or Listeria innocua were exposed to PL treatments (4, 6, or 8 J cm^?2 fluence) and kept cold at 4 °C for 20 days. L. innocua and E. coli counts, gases in the headspace of the containers (O₂ and CO₂), pH, titratable acidity, and soluble solid content were monitored throughout the cold storage. The PL treatments reduced significantly (p < 0.05) initial loads of both microbes. The effect of the PL fluence on the survival number of microoganisms was described by a log-linear model (R ² = 0.849–0.999). At any fixed time within the cold storing, the microbial counts for untreated samples were always higher than those cut tomatoes that had been previously PL-treated. The behavior of L. innocua and E. coli during the storage were well adjusted (R ² > 0.930) by Gompertzian models; the studied microorganisms exhibited different patterns during the storage period. On the other hand, O₂ and CO₂ partial pressures in containers with fresh-cut tomatoes were also significantly affected by PL treatments (p < 0.05). The highest PL fluence caused the greatest changes of O₂ and CO₂ contents. In addition, the application of PL triggered an acceleration of the O₂ consumption during the cold stage. PL treatments might be used to effectively extend the safety of fresh-cut tomatoes over 12 days of storage against E. coli and L. innocua growth.     

Influence of 10-MeV E-Beam Irradiation and Vacuum Packaging on the Shelf-Life of Grass Carp Surimi

The effects of 10-MeV E-beam (0, 1, 3, 5, and 7 kGy) irradiation and vacuum packaging on extending the shelf-life of grass carp surimi stored at 4 °C were evaluated basing on the total viable counts (TVC), physiochemical 2-thiobarbituric acid reactive substance (TBARS), total base nitrogen (TVB-N), biogenic amines (BAs), texture (TPA) and color, and sensory changes in surimi samples. The results showed that comparing the control samples, the TVC and TVB-N content in surimi were significantly (p?<?0.05) decreased by irradiation with different doses. Irradiation significantly (p?<?0.05) inhibited the increase of putrescine (PUT), cadaverine (CAD), histamine (HIM), and tyramine (TYM) contents during storage. However, these parameters were significantly (p?<?0.05) increased with storage time. After irradiation, the samples generally had higher lightness and lower a ^* and b ^* values and lower hardness and chewiness significantly (p?<?0.05). Based on the sensory analysis, unfavorable ‘metal odor’ or ‘irradiated odor’ was observed in surimi irradiated at 5 and 7 kGy.     

Thermal transition and thermo-physical properties of potato (<Emphasis Type="Italic">Solanum tuberosum L</Emphasis>.) var. Russet brown

Potatoes are an important food in many regions of the world and are commonly used in a variety of food products. Thermal transition and thermo-physical properties of potatoes are important in order to design efficient food processes and select appropriate storage conditions. In this study, we determined the thermal transitions and thermophysical properties of raw and blanched/par-fried potato for a temperature range of ??32 to 21.1 °C. Using differential scanning calorimetry, we found an initial freezing point (T_f) at ??1.8?±?0.1 °C, an onset of melting (T_m^′) at ??9.9?±?0.2 °C and an unfreezable water content (X^′_w) for maximally freeze-concentrated raw potato at 0.21 kg water/kg potato. Corresponding values for blanched/par-fried potatoes were ??0.9?±?0.1 °C, ??11.0?±?0.2 °C and 0.18 kg water/kg potato. Results show that an increase in solids content decreased T_f of both raw and blanched potatoes. We modelled the relationship between them using the Chen model. The apparent specific heat (C_app) increased around T_f to 31.7?±?1.13 kJ/kg K for raw potato and 26.7?±?0.62 kJ/kg K for blanched/par-fried potato. For frozen raw potato at ??32 °C, thermal diffusivity (α) was 0.89?±?0.01?×?10?^?6 m²/s and thermal conductivity (k), 1.82?±?0.14 W/m K, respectively. These values were higher for frozen raw potato than for the unfrozen raw potato (0.15?±?0.01?×?10?^?6 m²/s and 0.56?±?0.08 W/m K, respectively at 21.1 °C). The apparent density (ρ) of frozen raw potato (992?±?4.00 kg/m³ at ??32 °C) was less than that for unfrozen raw potato (1053?±?4.00 kg/m³ at 21.1 °C), and a similar trend was obtained for blanched/par-fried potato (993?±?2.00 kg/m³ at ??32 °C and 1188?±?7.00 kg/m³ at 21.1 °C, respectively). This study established a correlation between thermo-physical properties and temperature. Findings may be used to inform the design and optimization of freezing processes and frozen storage for potato products.     

Combined Application of Fluorescence Spectroscopy and Chemometrics Analysis in Oxidative Deterioration of Edible Oils

Combined methods of fluorescence spectrometry with chemometrics were used to monitor oxidation deterioration of edible oil. Synchronous and three dimensional fluorescence spectroscopy techniques were proposed for monitoring palm oil, camellia oil, sunflower oil and perilla oil during oven accelerated oxidation. Principal component analysis plot of fluorescence intensity (λex = 320–700 nm) clearly showed oxidative evolution of oils over heating time. High saturated or monounsaturated oils exhibited high regression coefficients between peroxide values and fluorescence intensity (R ²  = 0.973 for 400 nm in palm oil; R ²  = 0.956 for 370 nm in camellia oil). High diunsaturated oil exhibited high regression coefficient between nonpolar carbonyl compounds and fluorescence intensity (R ²  = 0.970 for 370 nm in sunflower oil). High triunsaturated oil exhibited high regression coefficient between p-anisidine value and fluorescence intensity (R ²  = 0.938 for 665 nm in perilla oil). In conclusion, Fluorescence spectroscopy is a rapid and green nondestructive method for oxidation monitoring. Differences of fatty acid compositions played key rules in formation of oxidation products and evolution of fluorescence spectra.     

Verification of 5-Methyltetrahydrofolic Acid in Nutritional Products

A simple method for the verification of supplemental (6R,S)-5-methyl-5,6,7,8-tetrahydrofolic acid, “5-MTHF,” in nutritional products is described. Nutritional product samples are prepared for the liquid chromatographic/fluorescence detection (LC/FLD) determination of 5-MTHF by buffer dilution, 10-min centrifugation, and syringe filtration. Method performance has been defined by assessments of 5-MTHF linearity (r ² averaged 0.9999 ± 0.0001, and all relative calibration errors averaged ≤0.6%, for ten consecutive six-point standard curves), intermediate precision (rsd = 1.1%, n = 9, for three products fortified at ～1.73 μmol/kg = ～795 μg/kg, tested on each of 3 days), accuracy (spike recovery average = 92.8 ± 1.0%, n = 9, for nutritional products spiked with 5-MTHF at ～1.73 μmol/kg, or ～795 μg/kg), and selectivity (absence of interference from reagent blanks, and from four compounds structurally related to 5-MTHF). The 5-MTHF recovery, as % of unheated controls, from a simulated heat treatment (20 min at 120 °C) averaged 99.1 ± 0.6%, n = 4. The limits of 5-MTHF detection (S/N = 3) and quantification (S/N = 10) were experimentally determined to be 10 μg/kg (～0.020 μmol/kg) and 30 μg/kg (～0.060 μmol/kg), respectively (<10× the expected fortification rate). The method provides a simple and inexpensive means for verifying proper fortification, and for assessing the stability to processing and storage conditions, of free 5-MTHF in nutritional products. A finding of interest is the indication that liquid nutritional products may comprise a stable matrix for 5-MTHF fortification.     

Smart NMR Method of Measurement of Moisture Content of Vegetables During Microwave Vacuum Drying

Microwave drying is usually combined with vacuum environment in conjunction with hot air flow to draw the moisture rapidly. The moisture content of the vegetables undergoing drying is hard to measure online. This research designed a microwave vacuum drying (MVD)-low-field nuclear magnetic resonance (NMR) smart device and investigated the feasibility of NMR method for online measurement of state of moisture during MVD. The relation between the signal amplitude (A ₂) and the true moisture content (M ₁) of six kinds of vegetables (mushroom, carrot, potato, lotus, edamame, vegetable corn) was fitted to estimate if NMR can measure the M ₁ of vegetables directly. Results showed that A ₂ and M ₁ of different fresh vegetables had no single empirical mathematical model to fit. However, for each kind of these vegetables, the A ₂ and corresponding M ₁ in different MVD stages showed a significant linear relationship. The predicted moisture content (M ₂) of mushroom: M ₂ = 5.25351 × 10^?4 A ₂ ? 0.34042, R = 0.996; carrot: M ₂ = 5.78756 × 10^?4 A ₂ ? 0.14108, R = 0.998; potato: M ₂ = 3.10019 × 10^?4 A ₂ ? 0.10612, R = 0.991; lotus: M ₂ = 2.32415 × 10^?4 A ₂ ? 0.01573, R = 0.998; edamame: M ₂ = 3.13310 × 10^?4 A ₂ ? 0.4198, R = 0.996; vegetable corn: M ₂ = 1.69461 × 10^?4 A ₂ ? 0.09063, R = 0.995. The linear models between M ₂ and A ₂ were able to estimate the end point (M ₁ < 8%) of MVD with a high accuracy (P > 0.950).     

Effects of Oxygen and Water Vapor Transmission Rates of Polymeric Pouches on Oxidative Changes of Microwave-Sterilized Mashed Potato

Polymer-based packaging with low oxygen (OTR) and water vapor transmission rates (WVTR) can be used to limit oxidative chemical changes in packaged foods, especially for the 3- to 5-year shelf life required for military rations and long-duration space foods. Microwave-assisted thermal sterilization (MATS) produces higher quality food with a potentially longer shelf life as a result of volumetric heating and the associated shorter process time. This study investigated the effects of the package-MATS process interactions and the resultant package barrier properties on food quality, using a mashed potato model food following MATS process of F₀?=?9 min for 12 weeks at 50 °C. Two poly ethylene terephthalate (PET)-based (MFA, MFC) and one ethylene vinyl alcohol (EVOH)-based (MFB) retort pouches were tested, with OTRs of 0.20, 2.11, and 0.07 cc/m²·day and WVTRs of 2.64, 1.78, and 0.29 g/m²·day for MFA, MFB, and MFC, respectively; a foil double-sealed MFA pouch served as a control (MF0).Barrier properties did not influence oxygen content in polymer pouches during storage (p?>?0.05). From the third week to the fifth week of storage, significant differences (p?<?0.05) were observed in total color difference (ΔE) and oxidation indicators (TBARS, hexanal, and nonanal). The mashed potato treated in higher barrier property pouches exhibited less color change and oxidation than those in lower barrier property pouches. The performance of the MFC pouch was similar overall to that of the metal pouch. These findings suggested that high-barrier packages are suitable for MATS or other commercially sterile foods, particularly for long shelf-life purpose.     

A Functional Smoothie from Carrots with Induced Enhanced Phenolic Content

Carrots are worldwide highly consumed due to their sensory characteristics and health-promoting properties. However, their low phenolic/antioxidant levels may be highly increased with abiotic stresses. Accordingly, phenolic/antioxidant enhancements and related phenylalanine ammonia-lyase (PAL) activity of carrot shreds under different treatments (UV-C radiation and hyperoxia conditions) were studied after a pre-enrichment incubation of 72 h at 15 °C. Subsequently, a carrot smoothie prepared from enriched carrot shreds was heat-treated (90 °C for 30 s) and stored at 5 °C up to 14 days. Heat-treated smoothies showed a good physicochemical and microbiological quality (<6 log CFU g^?1) after 14 days at 5 °C, although those non-irradiated samples registered lower psychrophilic and yeast and mold levels. Heat-treated smoothie from non-irradiated shreds stored under hyperoxia conditions showed the highest total phenolic content of 13.82 mg chlorogenic acid equivalent (ChAE) kg^?1 fw (87 % chlorogenic acid) after 14 days at 5 °C. Total phenolic content was in accordance with PAL and total antioxidant capacity. Conclusively, a pre-enrichment incubation of carrot shreds under hyperoxia conditions allowed to obtain a functional smoothie with high phenolic levels and good microbiological and physicochemical quality up to 14 days at 5 °C.     

Ohmic Heating Behaviour of Cabbage and Daikon Radish

Shredded cabbage (50 % v/v) and Daikon radish cubes (57 % v/v) with different salt concentrations (0.15, 0.5, 1, 1.5, and 1.85 %) were heated from 30 to 70 °C in a static ohmic heating cell at different voltages (65, 80, 100, 120, and 135 V) and frequencies (60, 2070, 5030, 7990, and 10,000 Hz) to evaluate their ohmic heating behaviour. Radish heated under 1.5 % salt, 120 V and 7990 Hz or 1 % salt, 135 V and 5030 Hz conditions gave the shortest heating time of 6 min from 30 to 70 °C, and cabbage gave the longest time of 128 min at 0.15 % salt, 100 V, and 5030 Hz. Regression models of heating rate as a quadratic function of the sample temperature gave R² >0.98. The general trend observed was that the magnitude of the heating rate increased with frequency at high voltage but decreased at low voltage for cabbage, while the opposite trend was observed for radish. Heating was more efficient at higher salt concentration and applied voltage. Radish heated more rapidly than cabbage. A slight slope change was observed in all cases between 50 and 60 °C. The response surface models revealed linear, cross products and quadratic effects to be significant with R ² over 0.98.     

Bio-transformed sawdust by white rot fungi used as a carrier for plant growth-promoting bacteria

This study assessed the bio-transformation of sawdust wood waste by a white rot fungi consortium and explores the use of the final product as a carrier for plant growth-promoting bacteria. During 75 days, Tabebuia roseae and Eucalyptus pellita (1:1) sawdust wood were used as growing substrates for Ganoderma lucidum, Pleurotus ostreatus, Trametes versicolor and Phanerochaete chrysosporium. Then, bio-transformed sawdust was evaluated as carrier of two strains of Enterobacter sp. and one strain of Stenotrophomonas maltophilia. Biologic activity and viability were determined at two storage temperatures (23–4 °C) for 60 days. Sawdust mixture was bio-transformed by white rot fungi. After 45 days, the carbon/nitrogen ratio was reduced up to 46 %, and 4.8 mg/g of CO₂ of residue was produced. Enzymatic activities attained a peak of 36.7 and 0.8 U g^?1 for laccase and manganese peroxidase, respectively in 45 days. Population of plant growth-promoting bacteria immobilized in bio-transformed sawdust wood decreased to 10⁵ CFU g^?1. However, this concentration and its biologic activity remained stable at 23 °C.     

Effects of <Superscript>60</Superscript>Co-γ and Electron Beam Irradiation on Storage Quality of <Emphasis Type="Italic">Panax ginseng</Emphasis>

Fresh ginseng was irradiated with ⁶⁰Co-γ or an electron beam at the dose of 2 and 4 kGy and stored at 2 °C. The quality of ginseng was evaluated after 60 and 120 days. Results suggest that when the storage time was 120 days, 2 kGy EI-treated ginseng had the lowest decay rate. During the 2 storage periods, the amounts of most of 9 ginsenosides decreased with an increase in the irradiation dose. The total saponin content of both ⁶⁰Co-γ-irradiated and EI-treated samples decreased with an increase in the irradiation dose. Significant (P <?0.05) upregulation of total polysaccharide content was observed in the 4 kGy EI samples after storage. Samples irradiated at 2 or 4 kGy by electron beam irradiation had the highest concentration of total saponin and ginseng polysaccharides, respectively. Levels of most of 17 amino acids decreased with the increasing irradiation dose. Exposure to irradiation doses up to 4 kGy affected the amino acid content of fresh ginseng. Ginseng irradiated at 4 kGy by ⁶⁰Co-γ irradiation and stored for 120 days had a significantly higher activity of superoxide dismutase (P <?0.05). A significant difference was observed in the total concentration of nucleosides and nucleobases between irradiated and un-irradiated ginseng samples (P <?0.05). These data suggest that the combination of a lower irradiation dose and low temperature is an optimal condition for extending the shelf-life of fresh ginseng without detriment to its ingredients.     

Stabilization of Refrigerated Avocado Pulp: Chemometrics-Assessed Antibrowning Allium and Brassica Extracts as Effective Lipid Oxidation Retardants

The effectiveness of Allium and Brassica extracts to inhibit the evolution of lipids oxidation in avocado pulp under refrigeration (storage at 4 °C) was studied. Onion, garlic, scallion, white cabbage, cauliflower, and Brussels sprouts extract were tested as preserving agents in refrigerated avocado pulp. Allium extracts promoted almost a 60% retention of the intrinsic anti-radical capacity of the pulps. Considering secondary oxidation effects, extinction coefficient at 270 nm shows that all treated pulps (except those with scallion addition) were acceptable at the 30th storage day (K ₂₇₀ < 0.22), but they were all significantly less oxidized than the untreated samples (K ₂₇₀ = 1.8) (P < 0.05). Garlic-treated avocado showed the highest antioxidant effectiveness, based on C=CH cis proportion (I _cis = 108.3), while samples with white cabbage extract presented the highest C=CH trans (I _trans = 5.7) proportion after 30 days. The PCA method was discriminant enough since 83.6% of the variance was explained by the first two principal components, allowing the samples to be grouped according to storage time and extract type. This study confirmed that the addition of garlic, onion, and cauliflower extracts enhanced lipid antioxidant properties in refrigerated avocado pulps.