Polyphenoloxidase activity from strawberry fruit (Fragaria ananassa,Duch., cv Selva): characterisation and partial purification

In this work, polyphenoloxidase (PPO) from Selva strawberry fruit (Fragaria × ananassa, Duch) was extracted, characterised and partially purified. The activity of PPO was analysed in crude extracts obtained from either fresh fruits or acetone powder. The presence of NaCl and Triton X‐100 in the extraction buffer caused a marked increase in enzyme extractability. The enzyme showed an apparent K_m value of 11.2 mM with pyrocatechol as substrate. The maximum enzyme activity was observed at 50 °C and pH 5.3–6.0 without SDS and pH 7.2 in the presence of SDS. The presence of SDS increased PPO activity at pH 7.2 but diminished it at pH 6.0. The enzyme showed high thermal stability and maintained activities equal to or greater than 50% of its maximum activity in the 2.6–9.3 pH range. One polyphenoloxidase isoenzyme was detected in crude extracts of all ripening stages, showing an isoelectric point of 7.3. The specific activity of PPO decreased continuously through fruit ripening. Maximum specific activities were found at the ‘small green’ and ‘large green’ ripening stages. A total enzyme extract was partially purified by means of (NH₄)₂SO₄ precipitation and cationic exchange chromatography in an FPLC system. The purification grade achieved was near 25. The partially purified enzyme showed an isoelectric point equal to 7.3 and a molecular mass of 135 ± 4 kDa for the native protein. © 2000 Society of Chemical Industry     

Aroma compounds in fresh and dried mango fruit (Mangifera indica L. cv. Kent): impact of drying on volatile composition

Volatile compounds from fresh and dried mango were extracted by the solvent‐assisted flavour evaporation (SAFE) technique and analysed by GC‐MS. Forty‐one and fifty five volatile compounds were identified in fresh and dried mango, respectively. Monoterpenes, followed by sesquiterpenes, lactones and alcohols were the major compounds. Drying induced substantial losses of several compounds. The total amount of volatiles decreased by about 59%. These losses could be mainly attributed to the evaporation of the volatiles during drying, the extent of which seemed to increase with the hydrophobicity and Henry's law constant of the compounds. However, new compounds appeared and enrichment of some compounds was observed after drying. Limonene, β‐myrcene, δ‐3‐carene, β‐caryophyllene, γ‐butyrolactone and 3‐methylbutyl butanoate were found to be flavour contributors in both products on the basis of the odour activity values (OAVs). Mesifuran displayed high OAV only in fresh fruit while hexanal and heptanal only in dried mango.     

Enhancing disease resistance in harvested mango (Mangifera indica L. cv. ‘Matisu’) fruit by salicylic acid

To learn how salicylic acid (SA) may affect disease resistance in mango, mango fruit (Mangifera indica L. cv. ‘Matisu’) were treated with 1 mmol L^?1 SA solution under vacuum infiltration for 2 min at a low pressure (?80 kPa) and for an additional 10 min at air pressure. The fruit were inoculated with anthracnose (Colletotichum gloeosporioides Penz.) spore suspension (1 × 10⁴ CFU mL^?1) and incubated at 13 °C, 85–95% RH. Disease incidence and lesion diameter in/on the SA‐treated fruit were 37.5% and 20.9% lower than that in/on control fruit on the 4th day of incubation. The study further showed that activities of defensive enzymes in the fruit were significantly enhanced by SA treatment. The activity of phenylalanine ammonia‐lyase (PAL) and β‐1,3‐glucanase in the SA‐treated fruit was over 6‐ or 0.9‐fold higher than that in control fruit on the 4th day after the fruit being treated with SA, respectively. Level of hydrogen peroxide (H₂O₂) or superoxide radicals (O₂^?) generation rate in SA‐treated fruit was 22.3% or 79.4% higher than that in controls on the 8th day after the fruit being treated with SA, respectively. These results suggested that PAL and β‐1,3‐glucanase, as well as H₂O₂ or O₂^?, may be involved in the enhancement of disease resistance in mango fruit. Copyright © 2006 Society of Chemical Industry     

Impact of Microclimate on Fatty Acids and Volatile Terpenes in “Kerman” and “Golden Hills” Pistachio (Pistacia vera) Kernels

Pistachio is an economically important nut crop in California. Since temperature variations among geographical locations can influence biochemical processes during fruit development, it is of great relevance to understand the impact of growing area over the components that define the nutritional and sensory characteristics of pistachio nuts. Changes in moisture, fat content, fatty acid composition and volatile terpenes were studied during kernel development for “Kerman” and “Golden Hills” varieties in two different California Central Valley microclimates, Lost Hills and Parlier. Moisture content decreased from July to September for both cultivars at both locations. Kerman had a higher moisture content at both locations compared with Golden Hills. Harvest time affected fat content only for Kerman, where the values increased drastically from 21‐July to 4‐Aug, then remained constant. Golden Hills’ fat content remained constant during the period of the study. The main fatty acid in pistachio oil is oleic acid (46% to 59%), followed by linoleic acid (26% to 36%) and palmitic acid (11% to 16%). C16:0, C16:1, C18:2, and C18:3 decreased with harvest time, while C18:1 increased. α‐Pinene was the most concentrated volatile among the cultivars and locations. It decreased with harvest time for both cultivars at both locations, ranging from 105 to 2464 mg/kg. At harvest, Golden Hills and Kerman at Parlier both had higher concentrations of α‐pinene than the two cultivars at Lost Hills. Our results demonstrate that microclimate affects biosynthesis of fatty acids and terpenes in pistachio kernels, the main compounds responsible for pistachio nutritional and sensory characteristics.     

Antifungal activity of chitosan and its application to control post‐harvest quality and fungal rotting of Tankan citrus fruit (Citrus tankan Hayata)

In this study, the antifungal activity of chitosan A (MW = 92.1 kDa) and B (MW = 357.3 kDa), with 94.2% N‐deacetylation were examined at various concentrations against fungi including Penicillium digitatum, Penicillium italicum, Botrydiplodia lecanidion and Botrytis cinerea. The effectiveness of these chitosans to control the post‐harvest quality of Tankan fruit, a popular sub‐tropical citrus fruit, was investigated. It was found that chitosan, depending on type and concentration, caused 25.0–90.5% growth inhibition on test organisms after 5 days of cultivation at 24 °C. Chitosan treatment significantly reduced (P < 0.05) the percentage decay of Tankan fruit during storage at 24 °C. After 42 days of storage at 13 °C, chitosan‐coated Tankan fruits were firmer, exhibited less decay and weight loss, and showed higher titratable acidity, ascorbic acid, and total soluble solids than the control fruit. Weight loss of Tankan fruits decreased as the concentration of chitosan was increased. On the other hand, chitosan A, regardless of concentration tested, was found to be more effective in retaining the firmness, titratable acidity and water content, total solid content and ascorbic acid content of Tankan fruits than chitosan B. Copyright © 2006 Society of Chemical Industry     

Effects of 1‐methylcyclopropene and gibberellic acid on ripening of Chinese jujube (Zizyphus jujuba M) in relation to quality

Overripening of Chinese jujube (Zizyphus jujuba M) fruit at the postharvest stage usually results in a dramatic decline in quality. The role of 1‐methylcyclopropene (1‐MCP) and gibberellic acid (GA) in fruit ripening of Chinese jujube during storage in relation to quality was investigated. Fruit ripening of jujube was significantly enhanced by ethylene, whereas rates of respiration and ethylene production of the fruit were reduced by 1‐MCP. Treatment with 1‐MCP or GA delayed the decreases in firmness and vitamin C and reduced the level of ethanol. Furthermore, the effectiveness of 1‐MCP was improved by replicate treatments during storage at 20 or 2 °C. In addition, treatment with GA + 1‐MCP resulted in additive beneficial effects on ripening inhibition of the fruit. Copyright © 2003 Society of Chemical Industry     

12‐Lipoxygenase activity in the muscle tissue of Atlantic mackerel (Scomber scombrus) and its prevention by antioxidants

Lipoxygenase was prepared from Atlantic mackerel muscle using differential centrifugation, ammonium sulphate precipitation and gel permeation (phenyl Sephadex G‐50) column chromatography. The crude lipoxygenase enzyme preparation was characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE), which showed two prominent bands with molecular weights of 119 and 125 kDa. Fractions collected from the chromatography column were tested for enzyme activity by reacting with arachidonic acid and determining the production of hydroxyeicosatetraenoic acid (12‐HETE) using reverse phase HPLC and GC–MS. The 12‐HETE peak was absent from the fresh arachidonic acid control sample and from arachidonic acid treated with heat‐inactivated lipoxygenase. Esculetin, a known inhibitor of lipoxygenase, inhibited the production of 12‐HETE from the reaction of lipoxygenase with arachidonic acid, thus confirming that the enzyme was lipoxygenase. The HETE peak was partially reduced in the presence of antioxidants, namely synthetic butylated hydroxytoluene (BHT) and natural antioxidants vitamins C and E. The presence of lipoxygenase in Atlantic mackerel muscle indicates the possibility that the lipid oxidation mechanism is initiated enzymatically in chilled and frozen stored fillets of mackerel and that this oxidative deterioration could be inhibited by antioxidants (BHT, vitamins C and E) which are used widely in the food industry. © 2001 Society of Chemical Industry     

L‐Phenylalanine ammonia‐lyase activity and concentration of phenolics in developing olive (Olea europaea L cv Arbequina) fruit grown under different irrigation regimes

Changes in L ‐phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) activity and total phenolic, ortho‐diphenolic and fat contents of olive flesh in response to different irrigation treatments applied to olive tree cv Arbequina were studied during fruit ripening. Results indicate that the fat content of olive flesh at harvest was not affected by irrigation, although olives from the most heavily irrigated treatment reached their final fat content (dry weight) earlier than those from other irrigation treatments. PAL activity and phenolic content, expressed on a dry weight basis, decreased during fruit development and were affected by irrigation, being lowered as the water supplied increased. Good correlations were established between PAL enzymatic activity and the polyphenol and ortho‐diphenol contents of olive flesh, indicating that PAL is involved in the phenolic metabolism of olive fruit. The phenolic content of the oil depends on the PAL activity in the fruit, which varies with changes in water status. © 2002 Society of Chemical Industry     

Some responses of Chrysanthemum morifolium (cv.“hurricane”), grown as a year-round crop in a peat-sand substrate,to micronutrients and liming

The effects of a fritted micronutrient mixture on the growth and flowering of spray chrysanthemums (cv.“Hurricane”) were studied in relation to pH in a peatsand substrate (3:1 by volume). The treatments consisted of three rates of application of a fritted micronutrient mixture (0, 200, 500 g/m³) in factorial combination with four rates of liming (average pH values 4.2, 5.0, 6.3 and 7.1). Five successive crops were grown under conditions, including controlled day-length, used commercially for year-round chrysanthemum production. Bud initiation and development were greatly delayed in the absence of micro-nutrients, particularly at high pH, and some plants failed to flower. The proportion of marketable sprays was decreased by omission of micronutrients (P<0.001) and by liming (P<0.001), and those that were saleable were reduced in size. Omission of micronutrients decreased the numbers of flowers per spray (P<0.001). Plants grown without added micronutrients developed more leaves and bracts on their lateral shoots (P<0.001), particularly at high pH (6.3–7.1); the interaction between lime and micronutrients was significant at P<0.01. Leaf samples were analysed for micronutrient content (B, Fe, Mn, Cu and Zn). Symptoms of boron deficiency (“quilling” of the petals) were recorded and shown to be significantly correlated with the boron content of the leaves (P<0.001). The copper content of plants grown without added micronutrients was well below the published critical level, and this deficiency is considered responsible for many of the effects observed.     

Structural changes,chemical composition and antioxidant activity of cherry tomato fruits (cv. Micro‐Tom) stored under optimal and chilling conditions

BACKGROUND: Cherry tomato fruits cv. Micro‐Tom, a model plant for tomato genetics, were analysed in order to determine the main structural and chemical changes under optimal and chilling storage conditions. The comparison of Micro‐Tom to standard tomato cultivars will give an insight into suitability of this dwarf cultivar as a model for studying the influence of low‐temperature conditions on tomato fruits. RESULTS: During chilling, fruit tissue was progressively destroyed due to the collapse of the deep layers of the pericarp. Chilling lowered the typical tomato kinetics of ripening in sugars (glucose, fructose, sucrose), organic acids (tartaric, malic, citric, ascorbic and succinic) and the antioxidants phenol and lycopene, while carotenoid synthesis seemed to be blocked. Glutathione level was elevated and the activity of ROS scavenging enzymes was altered. Essentially, Micro‐Tom fruits showed a quality evolution that was similar to that described for standard tomato cultivars. CONCLUSION: The cherry tomato cultivar Micro‐Tom could be used as a model for studying the influence of low temperature on biochemical and structural changes taking place during chilling injury conditions. Copyright © 2009 Society of Chemical Industry     

Alternative Sanitizers to Chlorine for Use on Fresh‐Cut “Galia” (Cucumis melo var. catalupensis) Melon

ABSTRACT: Chlorine is commonly used to reduce microbial load in fresh‐cut vegetables. However, the production of chlorinated organic compounds, such as trihalomethanes, which are potential carcinogens, has created the need to investigate the efficiency of nontraditional sanitizers and alternative techniques. The effects of 4 novel sanitizers were tested in fresh‐cut “Galia” melon: chlorine dioxide (ClO₂) at 3 mg/L, peracetic acid (PAA) at 80 mg/L, hydrogen peroxide (H₂O₂) at 50 mg/L, and nisin at 250 mg/L plus EDTA 100 mg/L (nisin + EDTA). A chlorine treatment (NaOCl at 150 mg/L) was used as a control. Pieces of melon were packed in polypropylene trays under passive modified atmosphere (3 to 4 kPa of O₂ and 10 to 11 kPa of CO₂) and stored up to 10 d at 5 °C. Microbial growth, firmness, respiration rate, gas composition, sensory evaluation, color, total soluble solids (TSS), and tritable acidity (TA) were evaluated at days 0, 7, and 10. The novel sanitizers PAA, H₂O₂, and nisin + EDTA, in the studied concentrations, reduced the microbial growth to a more efficient range than chlorine and ClO₂. In addition, those sanitizers delayed softness, did not affect the respiration rate, SST, or AT. The sensorial parameters were kept above the upper limit of marketability and they did not impart an “off flavor.” These sanitizers maintained quality and shelf life of fresh‐cut Galia melon for 10 d of storage at 5 °C. Nevertheless, other concentrations, in particular for ClO_2, could be tested to study an extended shelf life in melon pieces.     

Effect of cold‐shock treatment on chilling injury in mango (Mangifera indica L. cv. ‘Wacheng’) fruit

To investigate how cold shock may affect chilling injury in mango fruit (Mangifera indica L. cv. ‘Wacheng’), the fruit were treated for 3, 4 or 5 h at 0 °C, or treated for 8, 10 or 12 h at 4 °C, respectively, then transferred to 20 °C for 20 h prior to being stored at 2 °C, 85–95% RH. The chilling injury index of mango treated at 0 °C for 4 h was 59.7% lower than that of the control fruit directly stored at 2 °C, 85–95% RH. Some attributes were assayed in the fruit treated at 0 °C for 4 h. Ion leakage of the cold‐shock fruit at 0 °C for 4 h was 16% or 10% lower than that of the control on day 9 or day 12 of storage, respectively. Malondialdehyde content of the cold‐shocked fruit was 70% or 50% lower than that of the control on day 6 or day 12 of storage at 2 °C, respectively. Activities of catalase, ascorbate peroxidase, and contents of glutathione and phenolic compounds in the fruit during storage were all markedly enhanced by the cold‐shock treatment, whereas activities of superoxide dismutase, glutathione reductase and content of ascorbic acid in the mango were slightly influenced by the cold‐shock treatment. These results suggest that cold‐shock treatment may hold promise as an alternative approach to reduce chilling injury in mango fruit during cold storage. Copyright © 2006 Society of Chemical Industry     

Potent antioxidative activity of non‐polyphenolic fraction of green tea (Camellia sinensis) – association with pheophytins a and b

The antioxidative activity of green tea‐derived polyphenols known as catechins has been extensively studied. However, the antioxidative activity of the non‐polyphenolic fraction of green tea has been poorly elucidated and is the subject of the present study. The non‐polyphenolic fraction of green tea showed a significant dose‐dependent suppressive effect against the autooxidation of linoleic acid. The chlorophyll‐related compounds pheophytins a and b showed similar antioxidative activities in the same assay, much higher than those of α‐tocopherol and the green tea catechin (−)‐epigallocatechin‐3‐gallate (EGCG). The non‐polyphenolic fraction of green tea and pheophytins a and b exhibited suppressive activities against superoxide anion (${\bf O}_{2}ˆ{‐}$ ) generation in mouse macrophages induced by 12‐O‐tetradecanoylphorbol‐13‐acetate, showing higher activities than that of EGCG. These results suggest that the non‐polyphenolic fraction of green tea leaves has potent antioxidative activity and that this activity is associated with pheophytins a and b. © 2000 Society of Chemical Industry     

Chemical,technological, and nutritional characteristics of two lines of “farro” (Triticum turgidum ssp. dicoccum)

In recent years, the renewed interest for foods with a natural image has increased the demand for dry pasta produced from “hulled” wheat such as the Triticum turgidum ssp. dicoccum, also known as “farro”. In order to contribute to the general knowledge, two lines of farro were considered in this study. To have a comparison, an old cultivar of Triticum turgidum ssp. durum (Senatore Cappelli) in addition to a commercial semolina were also examined. All semolina samples were used to produce pasta samples. Results showed some differences among pasta samples that seem to be due not to the presence of specific protein subunits but especially to the quantitative ratio between the different subunits. Results also reconfirmed the role played by the drying technology that is able to affect the sensory characteristics of pasta products.     

Variation in 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and fructo‐oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time

Effects of storage temperature and duration on 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and trisaccharide (Tri) and fructo‐oligosaccharide (FOS) status in onion bulbs var Tenshin kept for 24 weeks at 10 and 20 °C were investigated. 1‐FEH activity peaked sharply after 10 weeks and seemed to be triggered by a decrease in sucrose content. 1‐KH activity increased during the first 8 weeks and remained stable during the last 8 weeks. Contents of Tri, FOS and total FOS decreased abruptly during the first 8 weeks; however, at 10 °C, contents of Tri, FOS (DP 3–12) and total FOS were lower than those at 20 °C. The consumption rate of fructo‐oligosaccharides also appeared to be higher at 20 °C than at 10 °C, despite the slight degradation in activities observed at this low temperature. 1‐FEH seems to be under the control of a triggering signal which induces its activity, and sucrose seems to be this biochemical signal which initiates dormancy release and the onset of sprouting, as found previously. Thus changes in carbohydrates seem to be a strong indicator of the end of the dormant state of the bulb and the beginning of the sprouting period. Copyright © 2004 Society of Chemical Industry