Quality attributes and cell wall properties of strawberries (Fragaria annanassa Duch.) under calcium chloride treatment

Effects of CaCl₂ (0%, 1% and 4%) treatment on quality attributes and cell wall pectins of strawberry fruits stored at 4 °C for 15 d were investigated. Strawberry firmness was not significantly affected by CaCl₂ treatment. Compared to the other groups, the 1% CaCl₂ group had better quality attributes, including decay rate, weight loss and soluble solids content. The treatment with 4% CaCl₂ inhibited weight loss but caused phytotoxicity. During storage, the chain widths and lengths of water-soluble pectin (WSP), chelate-soluble pectin (CSP) and sodium carbonate-soluble pectin (SSP) decreased. Strawberry softening seemed to be due to modifications of CSP and SSP, especially the side chains. CaCl₂ treatment significantly slowed the breakdown of CSP and SSP chains by strengthening the ionic crosslinkages among these pectin molecules. These results illustrate the fundamental CaCl₂ effects and will help improve the application of CaCl₂ to postharvest fruits.     

Postharvest shelf-life extension of avocados using methyl cellulose-based coating

Edible coatings regulate water vapor, oxygen and carbon dioxide transfer in or out of the produce thereby influencing the ongoing respiratory activity and produce quality. The objective of this study was to evaluate the effect of a methyl cellulose-based coating on the respiration rate, color and texture of avocados stored at room temperature. Avocados were initially surface disinfected, washed and air-dried. They were then immersed in the coating solution for 1 min at 20 °C, air-dried for 10 min and stored at 20 °C in an open box. At 2-day intervals, fruits were removed and evaluated for respiration rate, color and texture. Respiration rate was evaluated by measuring the rate of CO₂ produced from a given quantity of fruits per unit time. Color and texture of avocados were measured using instrumental techniques. Coated avocados demonstrated lower respiration rates, greener color and higher firmness as compared with the uncoated control during the entire storage. The appearance of brown spots and mesocarp discoloration normally associated with fruit ripening were delayed in the coated fruits.     

Packaging-specific influence of chitosan on color stability and lipid oxidation in refrigerated ground beef

We examined the influence of chitosan on lipid oxidation and color stability of ground beef stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with chitosan (1%) or without chitosan (control) were packaged either in high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), vacuum (VP), or aerobic packaging (PVC) and stored at 1 °C. Chitosan increased (P < 0.05) redness of patties stored in PVC and CO, whereas it had no effect (P > 0.05) in HIOX. Chitosan patties demonstrated lower (P < 0.05) lipid oxidation than controls in all packaging. Control patties in PVC and HIOX exhibited greater (P < 0.05) lipid oxidation than those in VP and CO, whereas chitosan patties in different packaging systems were not different (P > 0.05) from each other. Our findings suggested that antioxidant effects of chitosan on ground beef are packaging-specific.     

Physiological responses and quality attributes of ‘Kyoho’ grapes to controlled atmosphere storage

This research studied the physiological responses and quality attributes of Kyoho grapes (Vitis vinifera X V. labrusca) to controlled atmosphere storage. The grapes were stored for up to 60 days in 95% relative humidity with four different conditions, 4% O₂+9% CO₂, 4% O₂+30% CO₂, 80% O_2, and air, as control. The examined physiological responses and quality attributes included polyphenol oxidase (PPO) activity, ethanol concentration, fruit detachment force (FDF), firmness, color, soluble solid content (SSC), titratable acidity (TA), ascorbic acid concentration (Vc), and sensory quality. PPO activity, FDF drop and decay incidence when stored in 4% O₂+30% CO₂ were more effectively controlled, but unacceptable alcoholic flavor and browning were detected after 45 days, compared with those stored in 4% O₂+9% CO₂ or 80% O₂. The fruits kept in 4% O₂+9% CO₂ or 80% O₂ had good quality during 60 days of storage. The results suggested that high O₂ atmosphere exhibited a potential for maintaining the quality of ‘Kyoho’ grapes during long-term storage.     

Effect of a prestorage treatment with 6-benzylaminopurine and modified atmosphere packaging storage on the respiration and quality of green asparagus spears

Fresh green asparagus (Asparagus officinalis L.) spears were subjected to a prestorage treatment by dipping in 20 ppm 6-benzylaminopurine (6-BA) for 10 min. Treated and untreated spears were placed into low-density polyethylene (LDPE) bags with a thickness of 15 μm, in which a passive modification of the atmosphere was developed, or 25 μm, in which a gas mixture of 10 kPa O₂ + 5 kPa CO₂ was flushed and then the bags were stored for 24 days at 2 °C. Atmosphere composition, chlorophyll, ascorbic acid, fiber, color and sensory attributes were determined every 4 days. Throughout the storage period, O₂ level decreased from the initial values (21 kPa, 10 kPa) to 2.1–4.2 kPa in package without 6-BA treatment and to 4.9–6.8 kPa in package with 6-BA treatment. CO₂ level increased from the initial value (0 kPa, 5 kPa) to 5.5–7.2 kPa in packages without 6-BA treatment and to 4.1–6.1 kPa in packages with 6-BA treatment. In both packaging treatments, at the end of the 24 day storage period, the spears treated with 6-BA had a better color, firmness and overall appearance; moreover they retained more chlorophyll and ascorbic acid and they had less fiber.     

Sanitizer treatments alleviate lignification of sliced few-flower wildrice (Zizania latifolia Turcz.)

To investigate the effects of sanitation processing on the lignification of few-flower wildrice (FFW), fresh-cut FFW was treated with water (control), 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂, packed in polyethylene film bags and stored at 2 °C for 21 days. Firmness, lignin, cellulose, hemicellulose and lignin forming related enzymes activities were examined. Sanitizer treatments inhibited the increases of firmness, lignin and cellulose than the control. The changes of hemicelluloses did not show a difference between the control and PAA treatment. An increase in the activities of phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), and a reduction in catalase (CAT) and superoxide dismutase (SOD) activities, were detected in the sliced FFW in the incompatible interaction. Compared with the control, sanitizers suppressed the activities of PAL, POD and PPO, but enhanced the activities of SOD and CAT during 21 days of storage. These enzymatic activities varied with different sanitizers. These results show that 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂ sanitation processing can maintain tenderness, alleviate the lignification and fibrosis of fresh-cut FFW.     

Influence of γ-irradiation on the reactive-oxygen metabolism of blueberry fruit during cold storage

To explore a safe, environmentally friendly, and efficient preservation technology for blueberry (Semen trigonellae), “Bluecrop” blueberry fruits were treated with different irradiation doses. During cold storage at 0 ± 5 °C, the decay rate, fruit firmness, and indices relating to respiration and reactive-oxygen metabolism were detected regularly. Results showed that irradiation treatment with 1.0 kGy to 2.5 kGy doses was able to inhibit the respiration intensity, ethylene production, and the improvement of lipoxygenase (LOX) activity, thus reducing the increase of malondialdehyde (MDA) content and the permeability of cell membranes. In addition, irradiation treatment can improve the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) to eliminate, on a continual basis, the constantly generated superoxide anions (O₂⁻) and hydrogen peroxide (H₂O₂), keeping them at a low level: ultimately, this effectively guaranteed the storage quality and postponed the senescence process in the blueberry fruits. Meanwhile, those irradiated at 2.5 kGy presented optimal preservation effects as the respiration was inhibited to the utmost extent and the anti-oxidisation effect was enhanced. The results prove that the ⁶⁰Co γ-irradiation treatment at proper doses is an effective method of storing post-harvest blueberry fruits at low temperatures.     

Improved keeping quality of minimally fresh processed celery sticks by modified atmosphere packaging

Recommended storage conditions of green celery sticks are 4 °C for 10 days, but there are no reports about optimal modified atmosphere packaging (MAP) conditions to preserve them longer. The objective of this research was to describe the gas composition of MAP generated by two polymeric films and its effects on chemical, sensorial and microbial quality, and physiological disorders of celery sticks stored at 4 °C for 15 days. Green sticks of 15-cm length of ‘Trinova’ cv. were placed in hermetically sealed plastic bags: low-density polyethylene, oriented polypropylene (OPP) and polyethylene-perforated bags as control (air). The O₂ and CO₂ concentrations, soluble solid content, pH, titratable acidity, colour, sensorial quality and sugar and organic acids contents were monitored. Compared to the control, both MAP treatments improved the sensory quality, avoided the loss of green colour, decreased the development of pithiness and retarded the growth of microorganisms. In any treatment neither off-odours nor off-flavours were detected. After 15 days at 4 °C within the OPP bags a steady-state atmosphere of 6 kPa O₂+7 kPa CO₂ was reached and celery sticks stored under these bags showed the best quality.     

Monitoring of firmness evolution of peaches during storage by combining acoustic and impact methods

Firmness is a very important quality property in peach. The storage of peach affects its subsequent softening process and shelf life. The temperature and duration of storage mainly influence the firmness of stored fruit, and monitoring the evolution of fruits enables producers to manage its commercial life. The objective of the present study was to use non-destructive acoustic and impact tests to estimate firmness of peaches and to elucidate the influence of storage temperature and of time on the softening process of peach. Continuous and classification models based on variables obtained from non-destructive methods were developed. Parameters obtained from non-destructive methods were compared to destructive reference tests. The maximum force in ball compression correlated well with the maximum acceleration from impact test (r² = 0.75), and with a band magnitude parameter from acoustic test (r² = −0.71). Combining impact and acoustic parameters, the multiple correlation coefficient increases up to 0.91 (adjusted R² = 0.82) in the prediction of the maximum force in ball compression. Classification models based on both non-destructive parameters and sorting peaches into two classes of firmness, showed scores of well classified higher than 90%.     

Shelf-life of a Greek whey cheese under modified atmosphere packaging

“Anthotryros” cheese was packaged under vacuum (VP) or modified atmosphere (MAP) and stored at 4 or 12 °C. MAP mixtures were 30%/70% CO₂/N₂ (M1) or 70%/30% CO₂/N₂ (M2), while VP was taken as the control sample. Microbiological results showed that M1 and M2 delayed microbial growth compared with VP samples. Of the two modified atmospheres, gas mixture M1 was the most effective for inhibition of growth of mesophilic bacteria. Based primarily on sensory evaluation, the use of both MAP conditions extended the shelf-life of fresh Anthotyros cheese stored at 4 °C by ca. 10 days (M1) or 20 days (M2) compared with VP, and by ca. 2 days (M1) and 4 days (M2) at 12 °C, with cheese maintaining good sensory characteristics.     

Storage quality of strawberry fruit treated by pulsed light: Fungal decay,water loss and mechanical properties

The effect of different pulsed light (PL) doses (2.4–47.8 J/cm²) on water loss, fungal spoilage, mechanical properties and structure of strawberries stored for up to 8 days at 6 °C was studied. Incidence of postharvest molds on strawberry fruits was reduced by over 16–42% with PL application. There were no significant differences in maximal rupture force (F_R), mechanical work (W) and deformability modulus (E_d) values between treated and untreated fruits immediately after treatments. After 8 days storage at 6 °C, untreated strawberries showed a pronounced softening (≈ 48% reduction in F_R), but stored strawberries exposed for 10 s and 40 s to PL presented slight or not significant changes in the mechanical parameters regarding day 0, while F_R and W values of 20 s-PL treated samples were increased by 35% and 88% compared to those at 0 day storage. Micro and ultrastructure changes evaluated by LM and TEM images demonstrated ITW cell wall strengthening and a major integrity of walls of hypodermis cells induced by PL stress, while cell wall disassembly and reduction of cell-to-cell contact were detected in stored untreated fruit. There were no significant differences in weight loss among untreated and PL treated fruits after storage, excepting at the highest PL dose. PL technique would be able to simultaneously provide disinfection and delete softening of the tissues along cold storage. Present results make this non-thermal, residue-free alternative promising for extending shelf-life of traditional and organic strawberry production.Industrial relevanceThe present results demonstrated that pulsed light (PL) treatment is a promising alternative for extending the shelf-life of strawberries. A decrease in fungal incidence and a depletion of softening, important factors which limit the strawberry postharvest storage life, were achieved by the application of PL.     

Effects of postharvest hot air treatments on the quality and antioxidant levels in tomato fruit

‘Rhapsody’ tomatoes heated for 24 h in air at 34 or 38 °C were compared to fruit heated in 5% O₂ at 38 °C in order to determine if heat treatment applied in reduced O₂ pressure might reduce stress-related oxidative changes that sometimes accompany heat injury. Fruit were subsequently stored at 4 or 10 °C for up to 30 d. Unheated fruit and those heated in air at 34 °C for 24 h developed the best colour during storage at 10 °C. Storage at 4 °C inhibited carotenoid development in all treatments. Fruit heated in air or in 5% O₂ lost the most ascorbic acid and isoascorbic acid. Glutathione reductase activity at the end of storage was similar in all fruit, while glutathione S-transferase activity was higher in fruit that had initially been heated in 5% O₂. Heating of ‘Rhapsody’ tomato fruit in air at 34 °C for 24 h prior to storage at 10 °C for up to 30 d resulted in the least losses in antioxidant content, and fruit colour developed adequately. Reduced O₂ neither improved the efficacy of the heat treatment in reducing chilling injury nor protected tomato fruit from the negative effects of heat treatment.     

Effect of carbon monoxide in modified atmosphere packaging,storage time and endpoint cooking temperature on the internal color of enhanced pork

The objective of this research was to evaluate the effects of gas atmosphere, refrigerated storage time, and endpoint temperature on internal cooked color of injection-enhanced pork chops. Enhanced chops were packaged in 0.36% CO/20.34% CO₂ (CO-MAP), 80% O₂/20% CO₂ (HO-MAP), or PVC-overwrapped (PVC-OW; controls), stored at 4 °C for 0, 12, 19 or 26 days, displayed for 2 days then cooked to six endpoint temperatures (54, 60, 63, 71, 77, and 82 °C). L¹, a¹, and b¹ values, hue angle and chroma were determined on the internal cut surface of cooked chops. Chops packaged in CO-MAP had the highest a¹ values; a¹ value began increasing on day 14. The lowest hue angles occurred in chops cooked to lower endpoint temperatures. Chops in CO-MAP had lower hue angles and higher chroma than those in HO-MAP and PVC-OW. Above 71 °C, hue angle and chroma increased. Overall, CO-MAP packaged chops stored for longer time periods then cooked to lower endpoint temperatures appeared reddest. HO-MAP packaged chops were less red, did not change over time, and appeared more well done at lower endpoint temperatures than those in other gas atmospheres. CO-MAP packaged chops retained redness even after cooking at 82 °C.     

Effects of heat treatment on atmospheric composition and color of peeled white asparagus in modified atmosphere packaging

Freshly harvested spears of white asparagus were subjected or not to heat treatment by immersion in a hot water bath at 55 °C for 3 min, then left unpeeled or were peeled before wrapping in 16 µm stretch film and stored at 3 °C for 6 days. During storage, the atmosphere within the packages was sampled for O₂, CO₂ and C₂H₄ determination, while spear fresh weight, color and anthocyanin content at the 3 cm apical peel segments were determined before and after storage. The results showed that CO₂ concentration in packages of white asparagus spears was not greatly influenced by peeling or heat treatment. On the other hand, a higher package O₂ depletion of treated (peeled or heated) spears was observed. Peeling also resulted in an increase of ethylene peak concentration, indicating wound-induced ethylene production, which was suppressed by heat treatment. The initial color of the whole spear was retained, while the appearance of a violet coloration on the spear tip was prevented by heat treatment in both unpeeled and peeled spears.Industrial relevancePeeled white asparagus has drawn the attention of industry as a novel lightly processed product. The combination of heat treatment with modified atmosphere packaging (MAP) could be used to improve the storage life of this product. Moreover, both peeling and heat treatment cause changes in ethylene production and respiration rate of asparagus spears and this information could be useful for development of novel application to MAP design for lightly processed (peeled) white asparagus.     

Influence of relative humidity on carbon dioxide sorption in wheat gluten films

The influence of relative humidity (RH) on carbon dioxide sorption at 10⁵ Pa in wheat gluten films (WGF) was investigated in the range of 0–96% RH at 25 °C. The amount of water sorbed by these protein based films reached up to 60% of the dry weight at 96% RH. Carbon dioxide sorption increased with water content, ranging from 2.8 × 10⁻⁴ to 1.9 × 10⁻² mol Pa⁻¹ m⁻³ respectively at 0% and 96% RH. This behavior was tentatively explained on the grounds that sorbed water enhanced carbon dioxide accessibility to protein active sorption sites. The dependence of both the solubility and the diffusivity coefficients of CO₂ and O₂ on WGF water content explains the very good permselectivity of these films observed at high RH values (22 at 93% RH and 25 °C).     

Beta-lactoglobulin–polysaccharide complexes as nanovehicles for hydrophobic nutraceuticals in non-fat foods and clear beverages

For enrichment of non-fat clear drinks with hydrophobic nutraceuticals (HN), vitamin D₂ (VD₂), a model HN, was successfully entrapped within electrostatically stable nanoparticles ?50–70 nm in size. The particles, having electrophoretic mobility more negative than ?3 × 10^?8 m² V^?1 s^?1, comprised β-lactoglobulin (β-Lg) to which the HN was bound, and excess of a polyanionic polysaccharide (low methoxyl pectin), which provided electrostatic stability. As pectin concentration increased in 0.05% β-Lg solutions and pH 3.5–4.5, coacervation and turbidity first increased, but dropped beyond 0.01% pectin. The lowest turbidity, of about 0.035, was obtained at pH 4.25 and 0.05% pectin. As pH was increased from 3.5 to 4.25 the minimal particle size decreased and solutions became clearer. Optimal systems obtained were transparent, and may be suitable for enrichment of clear acid beverages. The nanocomplexes provided better protection to the vitamin against degradation than β-Lg alone, and stability was significantly better than that of unprotected vitamin dispersed in water.     

Development of potentially synbiotic fresh-cut apple slices

The aim of this study was, to develop potentially synbiotic fresh-cut apple wedges by applying probiotic bacteria (Lactobacillus rhamnosus GG) and prebiotics in the form of oligofructose and inulin. An assessment of the quality, sensory, polyphenol and volatile attributes of synbiotic and probiotic samples was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14 days storage period and an intake of 100 g of apple supplies 2–3 g of prebiotics. All samples sets contained ca. 10⁸ cfu/g over the test period, which is sufficient for a probiotic effect, and is comparable to counts of probiotic bacteria in commercially available dairy products. Browning index, firmness, acidity and dry matter remained stable throughout the 14 days compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory assessment indicated acceptable quality of probiotic and synbiotic apple wedges. HPLC analysis showed levels of decrease in polyphenolic compounds. No difference was found between O₂ and CO₂ headspace concentration and volatile production of synbiotic samples and samples only treated with probiotics.     

Studies on the anthocyanin profile and biological properties from the fruits of Acanthopanax senticosus (Siberian Ginseng)

The anthocyanin profile and biological activities, including antioxidant, xanthine oxidase inhibitory, angiotensin converting enzyme (ACE) inhibitory, and anticancer of Acanthopanax senticosus fruits were evaluated for the first time. The acidified 80% methanol extract of this species exhibited high biological properties at a concentration of 60 μg/ml. Moreover, cyanidin-3-O-(2″-O-xylosyl)-glucoside was identified using C₁₈ column chromatography, NMR spectroscopy, and HPLC-DAD-ESI/MS analysis. This compound was present at 5.2 mg/g, representing approximately 91% of the total peak area and possessed strong antioxidant effects against DPPH, ABTS, and hydroxyl radicals (IC₅₀ of 85.2, 43.7, and 126.6 μg/ml, respectively). Cyanidin-3-O-(2″-O-xylosyl)-glucoside also exhibited significant inhibitory activities against xanthine oxidase and ACE (IC₅₀: 55.5 and 47.1 μg/ml, respectively). Especially, LNCap (prostate), MOLT-4F (leukaemia), and ACHN (renal) cell lines exhibited potent anticancer effects, with IC₅₀ of 5.2, 11.2, and 22.5 μg/ml, respectively, in comparison with other cancer cell lines. Therefore, A. senticosus fruit may be utilised as an effective source for food and nutraceutical uses due to its high anthocyanin content as well as various biological properties.     

Effect of pectin methyl esterase (PME) and CaCl2 infusion on the cell integrity of fresh-cut and frozen-thawed mangoes: An NMR relaxometry study

This study describes the use of Nuclear Magnetic Resonance (NMR) relaxometry to understand the effect of pectin methyl esterase (PME) + CaCl2 infusion under different conditions on cell integrity of fresh-cut and frozen–thawed mangoes. Infusion experiments were performed at: atmospheric pressure, vacuum conditions of 50 kPa and 10 kPa. For NMR relaxometry experiments T₂ (spin–spin relaxation time), T₁ (spin–lattice-relaxation times) and 2D T₁–T₂ experiments were performed. Results showed that, as the severity of the vacuum treatment increased, the relaxation times changed significantly (p < 0.05). The number of compartments observed in 1-D relaxation spectra of fresh and frozen–thawed mangoes changed with different treatments. The changes in relaxation times were explained due to formation of a gel formed by the interaction of pectin and calcium. 2D T₁–T₂ relaxation maps showed that compartmentalization was retained after vacuum treatment even for frozen–thawed samples. The study showed that NMR relaxometry is a useful tool to analyze the cell integrity of mangoes exposed to different treatments.     

Silicon Rich Rice Hull Amended Soil Enhances Anthracnose Resistance in Tomato

Silicon (Si) has proven to be effective in controlling diseases in many crops and can be used as a substitute of fungicides. It has been shown that rice hull could be applied to the soil as a non-hazardous silicon rich source in crop production. This study was conducted to investigate the effect of half burnt rice hull (HBRH) as a silicon source in suppression of anthracnose in tomato and understanding underlying mechanisms of disease resistance. HBRH was made by burning raw rice hull at 250 ^°C for 15 minutes. Six different levels of HBRH: 0, 5, 10, 15, 20 and 25 g per 1 kg of soil were incorporated into soil along with Department of Agriculture (DOA) recommended levels of NPK fertilizers. The resistance against anthracnose disease was evaluated by measuring the lesion area of tomato fruits followed by the challenged inoculation with Colletotrichum dematium for 10 days after inoculation. The mechanism behind Si induced resistance was studied by measuring the fruit firmness and cuticle thickness (CT). A significant reduction (at P ≤ 0.05) of anthracnose disease (87 and 77%) was observed in inoculated fruits of 25 and 20 g HBRH per 1 kg of soil treatments. Onset of the disease was delayed by 4 and 3 days after inoculation in fruits obtained from 25 and 20 g HBRH treated plants compared to the control. The increase of fruit firmness and CT were significant in 25 and 20 g HBRH per 1 kg of soil provided fruits. Consequently, these results suggest that HBRH is a Si rich source and 20 g HBRH per 1 kg soil would be sufficient in suppressing tomato anthracnose caused by C. dematium and the resistance might have triggered with silicon induced thicken cuticle and increased fruit firmness.