Cell wall-modifying enzymes and firmness loss in ripening ‘Golden Reinders’ apples: A comparison between calcium dips and ULO storage

Calcium treatment and storage under ultra-low oxygen (ULO) conditions are common post-harvest practices aimed at delaying ripening-related softening of apple (Malus × domestica Borkh.) fruit, but the biochemical mechanisms underlying these effects have not been determined conclusively to date. In this study, commercially mature ‘Golden Reinders’ apples were dipped in 2% calcium chloride prior to storage at 1 °C and 92% RH under either regular air or ultra-low oxygen (ULO; 1kPa O₂:2kPa CO₂) for 19 or 31 weeks, and kept thereafter at 20 °C for 0, 7 or 14 days in order to simulate the usual marketing time. Cell wall composition and cell wall-modifying enzyme activities were determined in relation to fruit firmness. ULO-storage and calcium dips were effective for firmness preservation, seemingly due to decreased pectin solubilisation. β-Galactosidase, α-l-arabinofuranosidase and pectate lyase activities were correlated positively with firmness loss of ‘Golden Reinders’ fruit after storage.     

The role of peroxidase on the antioxidant potential of fresh-cut ‘Piel de Sapo’ melon packaged under different modified atmospheres

The effects of different initial in-package O₂ and CO₂ concentrations (2.5 kPa O₂ + 7 kPa CO₂, 10 kPa O₂ + 7 kPa CO₂, 21 kPa O₂, 30 kPa O₂ and 70 kPa O₂) on peroxidase activity, vitamin C content, total phenolics and antioxidant capacity of fresh-cut ‘Piel de Sapo’ melon have been investigated for 14 days at 4 °C. The radical scavenging activity of fresh-cut melon strongly increased after 9 days storage related to a synthesis of phenolic compounds, especially under 2.5 kPa O₂ + 7 kPa CO₂ atmospheres. Low O₂ levels best maintained vitamin C and phenolic content during the storage. However, stressful too-low O₂ and high CO₂ levels induced an important increase of peroxidase activity under 2.5 kPa O₂ + 7 kPa CO₂ atmosphere, which was directly related to changes of vitamin C throughout storage. Therefore, 70 kPa O₂ atmospheres are proposed to prevent anaerobic conditions during storage of fresh-cut melon and thus, reduce wounding stress and deteriorative changes related to high peroxidase activity in tissue.     

Cold storage conditions affect the persistence of diphenylamine, folpet and imazalil residues in ‘Pink Lady’ apples

‘Pink Lady^®’ apples (Malus domestica) fruit were harvested at commercial maturity treated with three different agrochemical products, and stored at 1 °C under either air or controlled atmosphere conditions (2.5 kPa O₂ + 3 kPa CO₂ and 1 kPa O₂ + 2 kPa CO₂) for 15 and 28 weeks. Diphenylamine, folpet and imazalil contents in both skin and flesh were simultaneously determined after cold storage plus a simulated marketing period of 1 or 7 days at 20 °C. Results showed that apples stored in 2.5 kPa O₂ + 3 kPa CO₂ retained higher contents of diphenylamine residues in comparison with those stored in 1 kPa O₂ + 2 kPa CO₂ or refrigerated air. Significant differences in imazalil skin contents were found throughout the simulated marketing period at 20 °C after storage for 28 weeks in controlled atmospheres.     

Modified atmosphere packaging improved quality of kohlrabi stems

To improve the keeping quality of the kohlrabi stems and avoiding wilting of the leaves, modified atmosphere packaging (MAP) with oriented polypropylene and amide-polyethylene copolymer bags was applied. Avoiding wilting of the kohlrabi leaves is crucial because European consumers consider the freshness of kohlrabi leaves as a key quality parameter. Whole kohlrabies were stored within, above-mentioned sealed bags, for 14 days at 0 °C and 95% RH, followed by 3 days at 10 °C. In the MA packages gas compositions of about 5 kPa O₂ and 10-15 kPa CO₂ were generated. The respiratory activity, C₂H₄ production, firmness (of stems and leaves), sugars, organic acids contents, as well as chemical and sensory quality attributes were monitored. The respiratory rate of the kohlrabi stems in air at 0 °C was 10-11 mg CO₂/kg/h with a C₂H₄ production lower than 0.05 μl/kg/h (traces). However, when the temperature was increased at 10 °C the respiration rate raised 3.5 folds. Acidity, pH, soluble solids, sugars and organic acids content and firmness did not show significant changes at the end of both cold storage and retail sale periods. MAP was very effective improving keeping quality of the stems and retarding wilting of the leaves. During the retail sale period at 10 °C, the bags must to be perforated to avoid anaerobic conditions.     

Phytochemical changes in fresh-cut jackfruit (Artocarpus heterophyllus L.) bulbs during modified atmosphere storage

A minimal process was carried out for pitted jackfruit (Artocarpus heterophyllus L.) bulbs using additives CaCl₂, ascorbic acid (AA), and sodium benzoate in combination with mild acidified conditions for storage under modified atmosphere (MA), i.e., 3 kPa O₂ + 5 kPa CO₂, gas mixture flushed polyethylene (GFPE) bags, polyethylene terephthalate jars with silicon membrane on lid and polyethylene bag with air. Samples devoid of any additive based pretreatment but packaged in similar MA conditions were used as experimental control. A restricted loss of around 7%, 8%, 43%, and 31% was found for total phenolics (TP), total flavonoids (TF), total carotenoids (TC), and AA contents respectively in the pretreated samples kept under GFPE bags towards the end of 35 days storage at 6 °C. Among the phytochemicals evaluated, the radical-scavenging activity showed the highest correlation (r = 0.979) with AA followed by TP, TF and TC.     

Effectiveness of ozone in combination with controlled atmosphere on quality characteristics including lignification of carrot sticks

Fresh-cut carrots were ozonized in water (1:2 w/v; @ 200 mg O₃/h) for 10 min and stored under controlled atmosphere (CA) conditions (2% O₂, 5% CO₂ and 93% N₂) at 6 ± 1 °C and 85% RH for up to 30 d. Ozonation was found to reduce lignification and maintaining the keeping quality of fresh-cut carrots during CA storage. The maximum decrease in respiration and ethylene emission rates were obtained by the combination of CA with ozone followed by CA alone and ozonation compared with the control samples kept under low temperature (6 ± 1 °C). Significant (p < 0.05) reduction in ascorbic acid, carotenoids and oxidative enzymes such as polyphenol oxidase (PPO) and peroxidase (POD) were observed due to ozonation and CA storage. The control of lignification by ozone in synergy with CA was characterized by decrease in L∗ values. The results highlighted the positive role of ozonation in combination with CA storage in controlling lignification and microbial spoilage of carrot sticks.     

Browning characteristics of fresh-cut ‘Tsugaru’ apples as affected by pre-slicing storage atmospheres

The change in browning characteristics of the slices processed from ‘Tsugaru’ apples stored at 0 °C for 5 months under controlled atmosphere (CA, 1 kPa O₂ + 1 kPa CO₂, 3 kPa O₂ + 3 kPa CO₂) or air has been investigated for 5 days at 20 °C. Respiration and ethylene production of the slices from apples stored in CA were retarded. Electrolyte leakage and browning index were lower in the slices from apples stored under CA than air. Vitamin C and phenolic contents in the slices from apples stored under air were maintained at higher level compared to the slices from apples stored under CA. Polyphenol oxidase activity in the slices was not affected by pre-slicing storage atmospheres. Therefore, the atmospheres of pre-slicing storage affected browning development in fresh-cut products of ‘Tsugaru’ apples and browning was found to be correlated with the levels of electrolyte leakage and phenolic compounds.     

Postharvest structural changes of Hayward kiwifruit by means of magnetic resonance imaging spectroscopy

In the present study magnetic resonance imaging (MRI) was used to evaluate the effect of storage conditions, 0 °C and 90% relative humidity (RH) or 20 °C and 70% RH, on minimal structural changes of kiwi tissue. Storage time was 35 days at 20 °C and 65 days at 0 °C including shelf life. Ethylene and respiration were followed during the experiment as well as commercial quality parameters such as sugars and firmness. MRI images weighted for proton density (ρ) and transverse relaxation times (T₂), were recorded after 10, 20, 35, 55 and 65 days. A decrease of the diameter was clearly visible in samples stored at 20 °C after 3 weeks and a coarse contour of the pericarp appeared after 40 days. Accumulation of water in the pericarp was found, suggesting a migration towards the outer regions occurs and that the fruit water loss due to evapo-transpiration is slower than the migration process. Samples stored at 0 °C showed no relevant changes in dimension and structural features for the whole period considered except after removal to shelf life. The observed variations of the internal morphology were correlated with the transverse relaxation times of defined areas and with softening of fruits. Measured T₂ profiles showed double-exponential decays, a fast- and a slow-relaxing component, indicating the existence of two different types of water molecules within cellular tissues: strongly and weakly bound, respectively. The relation among MRI data, ethylene and softening is discussed.     

Resistance of pathogenic bacteria on the surface of stainless steel depending on attachment form and efficacy of chemical sanitizers

Various bacteria including food spoilage bacteria and pathogens can form biofilms on different food processing surfaces, leading to potential food contamination or spoilage. Therefore, the survival of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Cronobacter sakazakii) in different forms (adhered cells, biofilm producing in TSB, biofilm producing at RH 100%) on the surface of stainless steel and stored at various relative humidities (RH 23%, 43%, 68%, 85%, and 100%) at room temperature for 5 days was investigated in this study. Additionally, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) on inhibiting various types of biofilms of E. coli O157:H7 and S. aureus on the surface of stainless steel was investigated. The number of pathogens on the surface of stainless steel in TSB stored at 25 °C for 7 days or RH 100% at 25 °C for 7 days was significantly increased and resulted in the increase of 3 log₁₀ CFU/coupon after 1 day, and these levels were maintained for 7 days. When stainless steel coupons were stored at 25 °C for 5 days, the number of pathogens on the surface of stainless steel was significantly reduced after storage at RH 23%, 43%, 68%, and 85%, but not at 100%. When the bacteria formed biofilms on the surface of stainless steel in TSB after 6 days, the results were similar to those of the attached form. However, levels of S. aureus and C. sakazakii biofilms were more slowly reduced after storage at RH 23%, 43%, 68%, and 85% for 5 days than were those of the other pathogens. Formation of biofilms stored at RH 100% for 5 days displayed the highest levels of resistance to inactivation. Treatment with the alcohol sanitizer was very effective at inactivating attached pathogens or biofilms on the surface of stainless steel. Reduction levels of alcohol sanitizer treatment ranged from 1.91 to 4.77 log and from 4.35 to 5.35 log CFU/coupon in E. coli O157:H7 and S. aureus, respectively. From these results, the survival of pathogens contaminating the surfaces of food processing substrates such as stainless steel varied depending on RH and attachment form. Also, alcohol-based sanitizers can be used as a potential method to remove microbial contamination on the surfaces of utensils, cooking equipment, and other related substrates regardless of the microbial attached form.     

Fruit quality and physiological responses of litchi cultivar McLean's Red to 1-methylcyclopropene pre-treatment and controlled atmosphere storage conditions

The effect of 1-MCP pre-treatment and two different controlled atmosphere storage conditions (CA-1, 17% O₂ + 6% CO₂; CA-2, 7% O₂ + 3% CO₂) on fruit quality parameters and physiological changes with respect to pericarp browning in ‘McLean's Red’ litchi were investigated. Fruits were pre-treated with 1-MCP (500 nl/l) and held at CA-1 or CA-2 for 21 d at 2 °C and at 90% RH. Stand-alone CA-1 or stand-alone CA-2 and the commercially adopted sulphur dioxide (SO₂) treatment were included in this study for comparison. Of the five treatments 1-MCP + CA-1 was most effective in preventing browning, loss of red colour (colour value a*) of the pericarp, ascorbic acid content; and retaining acceptable SSC/TA and taste. Fruit from 1-MCP + CA-1 showed higher overall acceptance after 21 d storage without any off-flavour according to the sensory panel data.1-MCP + CA-1 reduced the polyphenol oxidase (PPO) and peroxidase (POD) activity, retained membrane integrity and anthocyanin content during storage. Although SO₂ treatment prevents browning it showed negative effects on SSC/TA, taste and membrane integrity. Stand-alone CA-2 condition indicated higher pericarp browning, PPO, POD activity and loss of membrane integrity. Therefore, 1-MCP pre-treatment and CA-1 retains overall fruit quality for up to 21 d.     

Effect of oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydew melons

Cantaloupe and honeydew melon cultivars were processed and stored under a high oxygen passive modified atmosphere packaging (MAP) or reduced oxygen controlled atmosphere (CA; 5 kPa O₂ + 10 kPa CO₂ and balance N₂) for 14 days at 5 °C. Atmosphere did not affect softening rate or soluble solids content and had a negligible effect on colour. Volatile compounds known as flavour-important in melons were extracted using stir bar sorptive extraction (SBSE) and quantified via GC–MS. Acetate esters increased more in MAP than in CA. Non-acetate esters increased markedly in both cultivars and storage types. Alcohols were more abundant in honeydew than in cantaloupe. Aldehydes decreased during storage in both cultivars and storage types. Lower O₂ availability under CA conditions likely suppressed some of the esters relevant to the aroma of fresh-cut melon. Results suggest that package O₂ levels are more important in determining aroma than other quality attributes of fresh-cut melon, and high O₂ levels may be required to reveal desirable aroma compounds.     

Analysis of ginsenosides in Panax ginseng in high pressure microwave-assisted extraction

High pressure microwave assisted extraction (HPMAE) was applied to extract the ginsenosides from Panax ginseng root. The influences of extraction solvent, extraction pressure and extraction time were individually investigated. HPMAE has been compared with other extraction methods, including Soxhlet extraction, ultrasound-assisted extraction and heat reflux extraction. The determination of ginsenosides was performed by HPLC–ESI-MS. The results indicated that the HPMAE not only took a shorter time but also afforded higher extraction yields of ginsenosides, especially ginsenoside Rb₁, Rc, Rb₂ and Rd. Furthermore, the neutral ginsenosides and malonyl ginsenosides in Panax ginseng root extracts by HPMAE were investigated. The malonyl ginsenoside m-Rb₁, m-Rc, m-Rb₂ and m-Rd degraded in HPMAE at 400 kPa (109–112 °C) in 70% (v/v) ethanol–water and at 600 kPa (112–115 °C) in methanol, and transformed into corresponding neutral ginsenoside Rb₁, Rc, Rb₂ and Rd. Using water as extraction solution, the neutral ginsenosides degraded under HPMAE at 400 kPa (135–140 °C), and transformed into less polarity rare ginsenosides.     

Evaluation of modifiers for determination of V in parsley by GF AAS

The thermal behaviour of vanadium in the absence and presence of BaF₂, W and Rh as modifiers were evaluated for the direct determination of V in parsley slurries by GF AAS. For the sequence BaF₂, no modifier, W and Rh, the characteristic masses were 16, 17, 58 and 37 pg, and the RSD were 1.3%, 0.6%, 9.8% and 10.8%, respectively. BaF₂ and absence of modifier furnished the best thermal stability, signal profile, repeatability and characteristic mass. For slurries containing 0.5% (m/v), 0.2% (v/v) HNO₃, 0.05% (v/v) Triton X-100, the pyrolysis and atomisation temperatures were 1700 and 2600 °C, respectively. The method was applied for V in digests and slurries and results agreed at 95% confidence level. Spinach and tomato leaves standard reference materials were analysed and results agreed with certified values. Recoveries from 93% to 108% were obtained. The graphite tube lifetime and LOD was 250 firings and 0.94 μg L⁻¹, respectively.     

Different postharvest strategies to preserve broccoli quality during storage and shelf life: Controlled atmosphere and 1-MCP

Broccoli (Brassica oleracea var. italica) is a vegetable that requires the application of postharvest techniques to extend its marketability. Controlled atmosphere and 1-MCP treatments are most used to extend the shelf life of broccoli and reduce post-harvest deterioration. The aim of this study was to evaluate the visual, physicochemical and functional changes of broccoli head samples stored at 1–2 °C and 85–90% relative humidity (RH) in air (Control samples), under controlled atmospheres (10% O₂ and 5% CO₂) (CA samples) and treated with 1-MCP (0.6 μL/L). After storage all samples were maintained at 20 °C for 2 and 4 days, in order to assess their shelf life. The most suitable postharvest treatment to extend broccoli quality during storage and shelf life, in terms of maintaining the visual quality and reducing loss of health-promoting compounds, was achieved by storage under controlled atmosphere conditions. The use of 1-MCP reduced the loss of green colour and chlorophyll pigments, but only during cold storage not during shelf life at 20 °C.     

Assessment of the mechanical properties of Tarocco orange fruit under parallel plate compression

In this work the mechanical compressive properties of orange fruits of the Tarocco variety were assessed using a Universal Testing Machine, equipped with upper and lower plates made of transparent graduated Plexiglas® and three cameras positioned along the axis lines x, y and z. By submitting each fruit to different engineering strains (ε_z) along the z-axis in the range of 3-21% of the initial fruit height, the momentary contact area of each fruit under testing was precisely determined by approximating its outline to a polygon and reconstructing it via the Elliptic Fourier Analysis, or an ellipse inscribed in a bounding box. Both estimates yielded no statistically significant difference and varied linearly with ε_z. Their prediction using the ASABE Standard Method (2008), or assuming no variation in the volume of the fruit undergoing compression, resulted be under- or over-estimated by 45% or 19%, respectively. Use of image analysis allowed the apparent Poisson’s ratio and modulus of deformability (E_O) of the whole orange fruit to be estimated as equal to 0.16 ± 0.09 and 353 ± 3 kPa, respectively.By assimilating the orange fruit to a deformable membrane (flavedo) filled with an internal incompressible juice, it was possible to estimate the compressive stress acting on the equatorial horizontal cross-section of the epicarp only and thus estimate the apparent modulus of elasticity of the orange peel (=375 ± 33 kPa), and a burst pressure of 533 ± 103 kPa at a rupture strain ε_zR of 0.30 ± 0.03 for rind thicknesses ranging from 0.8 to 4.0 mm.     

Shelf-life extension of highbush blueberry using 1-methylcyclopropene stored under air and controlled atmosphere

The potential of 1-methylcyclopropene for controlling ripening in ‘Lateblue’ blueberry fruit was explored. After harvest, blueberry fruits were exposed to 1-MCP (0.3 and 0.6 μl l⁻¹). After treatment, samples were stored in air at 0 °C for 35 days and in a controlled atmosphere (3 kPa O₂ + 11 kPa CO₂) for 60 days. Quality parameters were monitored (weight loss, total soluble solids content, titratable acidity, firmness, anthocyanin content, phenolic content, total antioxidant capacity). Blueberries treated with 1-MCP showed a reduced weight loss during storage and a lower total soluble solid content compared to untreated fruit. High titratable acidity values were observed after controlled atmosphere storage, but no significant effect of 1-MCP on this parameter was observed. 1-MCP had no significant effects on anthocyanins, phenolics or antioxidant activities.     

Influence of the process parameters and sugar granulometry on cocoa beverage powder steam agglomeration

The objective of this research was to evaluate the effects of the steam agglomeration process variables on the characteristics of cocoa beverage powders. A pilot scale agglomerator was used in the tests. For the cocoa beverage powder formulated with granulated sugar, most common commercial product, the increase in solids feed rate (400–700 g/min) led to a decrease in the mean particle diameter (400 g/min – 564.70 μm, 700 g/min – 438.40 μm) and an increase in the dryer rotation (12–52 rpm) led to an increase in the product moisture (12 rpm – 1.52% w.b., 52 rpm – 1.88% w.b.). The changing from 1.0 × 10² to 1.8 × 10² kPa of the vapor pressure resulted in an increase in moisture of the cocoa beverage powder (1.0 × 10² kPa – 1.46% w.b., 1.8 × 10² kPa – 1.94% w.b.) and the intensification of the yellow color of the product (1.0 × 10² kPa – 14.51, 1.8 × 10² kPa – 15.17).     

Determination of lead and cadmium in food samples by the coprecipitation method

In this study, the coprecipitation method developed using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as coprecipitate carrier was used for the determination of trace lead and cadmium in various food samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was applied for the determination of Pb(II) and Cd(II) in salami, sausage, chicken, anchovy, spinach, cabbage, onion, dill, parsley, lettuce, tea and rice samples. The matrix modifiers were added as 50 μg NH₄H₂PO₄ + 3 μg Mg(NO₃)₂ for both Pb(II) and Cd(II). The signals were measured as peak area. The concentrations of Pb(II) and Cd(II) in the food samples were found to be in the range of 6.63 ng g⁻¹ (anchovy) −3.30 μg g⁻¹ (spinach) and 2.67 ng g⁻¹ (salami) −0.51 μg g⁻¹ (lettuce), respectively.     

Is the temperature-humidity index the best indicator of heat stress in lactating dairy cows in a subtropical environment?

Several temperature-humidity indexes (THI) have been used to estimate the degree of thermal stress experienced by dairy cows. The present objectives were to develop equations using meteorological variables that predicted rectal temperature of lactating cows in a subtropical environment and compare the goodness of fit of these equations to those using 8 different THI. Rectal temperature was measured between 1500 and 1700 h in 1,280 lactating Holstein cows in north central Florida between August and December. Meteorological data recorded in the barn where cows were located included dry bulb temperature (T_db), relative humidity (RH), dew point temperature, and wind speed. Wet bulb temperature was calculated. In the first series of analyses, regression analysis was used to model rectal temperature using the meteorological variables as well as THI. The r² using T_db (0.41) was slightly less than for models using all but one THI (r² between 0.42 and 0.43). The r² for equations using T_db could be improved by adding RH (r² = 0.43) or RH and RH² (r² = 0.44) to the model. In the second analysis, regression analysis was performed using forward selection, backward elimination, and stepwise selection procedures with the meteorological variables. All models gave a similar goodness of fit (r² = 0.44). An analysis of variance with rectal temperature as a class variable was performed to determine the least squares means of meteorological measurements associated with hyperthermia. A T_db of 29.7°C was associated with rectal temperature of 39°C, and a T_db of 31.4°C was associated with rectal temperature of 39.5°C. In conclusion, T_db is nearly as good a predictor of rectal temperatures of lactating Holsteins in a subtropical environment as THI. Estimates of values of meteorological variables associated with specific rectal temperatures should prove valuable in relating environmental conditions to the magnitude of hyperthermia experienced by heat-stressed cows.