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LA CONSERVAZIONE DELL’ACTINIDIA : FATTORI E TECNICHE PER LA QUALITÀ OTTIMALE
No full textKiwifruit storage: factors and technologies to achieve the best quality
Abstract
In Italy kiwifruit production was approximately of 4,400.000 tons in 2006. Most production is located in Central and Northern Italy. The great interest towards kiwifruit is because its sensorial aspects and nutraceutical content of vit.C, other than its long term storage capability, that makes this valuable kind of fruits available and exportable during the winter months.
The storage period greatly influences fruit ripening physiology, therefore its correct management has great incidence on the final quality of the product to offer to the consumer. Kiwifruit have a high starch content in the flesh before ripening, which is converted into sugars during the storage period. Consequently soluble solids content (SSC) increases after harvest and may reach more than double values during the first 1 to 2 months of storage. Meanwhile, titratable acidity decreases by as much as 50% of the preharvest content. Most dramatic change during storage is the reduction in flesh firmness, that declines by 30 to 50% each month of air storage at 0°C and 10 to 20% in Controlled Atmosphere (5% CO2 e 2%O2).
Kiwifruit are prone to mechanical and vibration injuries, showing in firm fruit (>60N) light whitish bruises. The white colour results from failure to convert starch to sugar in the injured cells. In softer fruit (< 30N), where flesh no longer contains starch, a translucent bruise results. This facts provide a compelling reason to harvest and market kiwifruit at the right firmness level to control damages.
Exposure to ethylene, even at very low levels (5 to 10 ppb) induces fruit softening and accelerates ripening. So far it is good practice to avoid ethylene exposure during harvest, transport and storage.
Kiwifruit take advantages of Controlled Atmosphere storage and the major benefits is a delay in flesh softening. Upon removal from CA conditions the fruit are firmer and retain a greater market life.
The present paper considers the pre and postharvest factors and the advanced and innovative storage techniques to achieve the best kiwifruit, in term of quality and nutraceutical content, to present to the consumer.
L’actinidia, con la produzione di 4.400.000 ql nel 2006, è una specie di grande importanza per il comparto ortofrutticolo nazionale e l’Italia ne è stato il primo produttore mondiale fino al sorpasso cinese del 2002. Il suo successo è sicuramente in gran parte attribuibile, oltre che alle sue qualità sensoriali e nutrizionali per l’elevato contenuto di vitamina C, al suo potenziale di conservazione di parecchi mesi che la rende uno dei più pregiati prodotti disponibili ed esportabili durante tutto l’inverno.
Il periodo di conservazione è una fase molto importante per la fisiologia di questo frutto e il suo corretto andamento ha riflessi fondamentali sulla qualità finale del prodotto. Il frutto dell’actinidia, infatti, converte la maggior parte dell’amido accumulato in pianta nel periodo di conservazione al freddo, raddoppiando o triplicando il suo grado zuccherino nei primo o secondo mese dopo la raccolta, quando contemporaneamente anche l’acidità titolabile diminuisce più del 50% dei valori preraccolta. Tuttavia il cambiamento più forte in questa fase è l’intenerimento, che aumenta del 30-50% per ogni mese di conservazione in atmosfera normale (aria) a 0°C, e del 10-20% in atmosfera controllata (5% CO2 e 2%O2).
Il frutto dell’actinidia è molto suscettibile ai danni meccanici e da vibrazioni, che si manifestano con aree discolorate o traslucide, la cui severità dipende molto dal livello di durezza del frutto al momento dell’impatto; quindi il valore ottimale di compattezza della polpa del frutto al momento della raccolta va oculatamente valutato per minimizzare i danni della raccolta. L’actinidia inoltre è molto sensibile alla presenza di etilene, anche a livelli minimi (2-5 ppb), che ne provoca un veloce intenerimento e ne accelera la maturazione, per cui vanno evitate tutte le esposizioni a questo gas, ponendo cura anche alle contaminazioni accidentali degli ambienti di raccolta, lavorazione e conservazione.
Poiché l’actinidia è una delle specie che maggiormente si avvantaggia della conservazione a lungo termine in atmosfera controllata, il presente lavoro considera le tecnologie, anche innovative, e i fattori pre e postraccolta più adatti a esitare al consumatore un prodotto di ottima qualità sensoriale e nutrizionale
Calcium physiology and metabolism in fruit trees
No full textCalcium plays an important role in plant growth and development. Its importance as a mineral nutrient has two main purposes: apoplastic and symplastic. Apoplastic calcium has an important structural and functional role in the plant cell walls and membranes. Cell wall is reach in pectinaceous materials that contribute to cell cohesiveness and is believed to constitute an important site of calcium interaction. Integrity of the membranes is important for maintaining its selectivity. In these cases a millimolar calcium concentration is necessary in order to fulfil its requirements as cementing material and as source of calcium readily accessible to membrane surface and subsequently to internal compartments. The symplastic concentration of calcium has to be maintained at the micromolar level to serve as an intracellular "second messenger". This is maintained through the action of different transport mechanisms localised on the membranes which extrude the ion from the cytosol towards the cell wall or other intracellular organelles. Transient increase in cytosolic calcium is the way to activate metabolic reactions in response to extra- or intracellular signals. Calcium alone or its complex with calmodulin activates protein kinases that through covalent modification of other target enzymes will modulate the physiological responses
Biochemical characterization of the mesocarp in distinct apricot (P. armeniaca) genotypes
No full textApricot fruit handling and shipping is often impaired by soft flesh texture. Within the apricot germplasm very diverse genotypes differing in mesocarp texture are found. The present study was undertaken to gain greater understanding of the biochemical and physical properties of these fruits. Fruits from fourteen apricot cultivars differing in flesh texture were tested at three different ripening stages (green, breaker and full ripe) for firmness and skin background colour and analyzed for soluble and insoluble pectins, total and pectin-bound calcium. Flesh firmness measurement by penetrometer was found unreliable for assessing flesh texture and compactness. The calcium increased in flesh throughout ripening, suggesting that uptake is active until the final stage of fruit development. Variability in flesh total calcium could not be associated per se to firmness or texture, although it could be very high in very firm cultivars. The allocation of calcium to pectins did not depend on flesh firmness or texture. Variability in pectins (particularly the water insoluble fractions) could possibly explain the high differences found in sensory evaluation of flesh texture in some very firm and compact apricots
The effect of calcium treatments on aspects of cell wall metabolism in apple cv. 'Braeburn'
No full text'Braeburn' apple is appreciated because of its 'crispy' texture and acid taste but it is very susceptible to several storage disorders, mealiness included, because of its low calcium content. Many attempts are in progress to improve calcium flesh concn. and thus its keeping quality. Aim of the present work is to study the capability of both field and posthavest treatments in keeping fruit quality during cold storage. 'Braeburn' apples field or postharvest treated with diverse calcium formulas and additives, were examd. for quality (total sol. solids, titratable acidity, flesh firmness and starch content), calcium content and cell wall compn. (cellulose, total, sol. and insol. pectins and neutral sugars) at harvest and after seven months of controlled atm. cold storage (ULO). Field and postharvest calcium treatments did not affect quality traits both at harvest and after storage, nevertheless they influenced calcium contents in fruit flesh and they modified cell wall compn. All field treatments increased fruit calcium content up to 10-60% and the effects lasted until the end of storage. Postharvest treatments increased cation level (8-60%) at the end of storage. Cellulose content increased for both treatments and the effect lasted during storage. Field supplies seemed to stimulate pectin biosynthesis also after harvest for long time, while postharvest treatments did not increase pectin biosynthesis but were very effective in preventing pectin solubilization. Field treatments reduced rhamnose content in stored fruits, thus reducing the side chain no. of polygalacturonic acid with the consequent increase of the pectic matrix cohesion to which ascribe the flesh crispness of this apple cultivar. Galactose, a basic component of pectin chains, was pos. affected by field supplies and its high level was maintained through the storage period. Postharvest calcium treatments did not increase galactose content, but were very active in keeping its level
Effects of postharvest treatments and storage conditions on chestnut quality
No full textInterest in chestnut is increasing because of both its healthy nutritional contents and curiosity about ancient traditional foods. Fruit is grown either for fresh market or for production of special and typical foodstuff. The nut loses viability rapidly after harvest due to fruit rots and insects and several storage methods have previously been applied to prolong its postharvest life. The present work considers two local chestnut cultivars (Catot and Platella) from Valle Camonica (Brescia, Northern Italy), grown at 900 m a.s.l. Nuts were treated (or not) with traditional curing (nine days submerged in water), hot (51°C) water for 45 min, NaHCO3 1% and stored for 60 and 105 days in cold room (1°C) equipped with two different Controlled Atmosphere conditions (CA1: 2.5 % CO2, 1.5 % O2; CA2: 20% CO 2, 2% O2). At harvest and following storage, fruit of cv Platella from control, cured and CA2 treatments, were peeled, sterilized, cut into halves, plated in Petri dishes and incubated at 24°C for 21 days to assess fungal contamination. Curing, heat treatment and CA2 were very effective in controlling fruit rots until December (60 days) then their effect decreased. CA2 maintained the best quality of fruits in term of freshness, taste and flavor. For example, in mid February (105 days) the chestnuts looked as fresh and bright as just picked nuts. Cured and heat treated fruits were respectively a little or very dry and NaHCO3 treatment had no effect in controlling fruit rots. The treatments seemed to exhibit a selective effect on diverse fungal contaminants; i.e. curing was efficacious in reducing contamination due to all fungi except from Penicillium spp., and CA gave excellent results, but it was ineffective in controlling Aspergillus niger. Apart from NaHCO3, the treatments were effective in controlling insect development
An in vitro approach to study ripening phenomena of fruits
No full textHuge fruit variability, long lasting times and big amounts of needed fruits are some drawbacks in studies of ripening physiology. The in vitro approach to this kind of problems helps to bypass many of them. This work presents two in vitro systems on tomato and apple pericarps useful to study the effects of divalent ions and heat treatments on enzyme activities and cell wall metabolism during fruit ripening. The effectiveness of both systems is compared with whole fruit response
Ascorbic acid content and senescence in blueberry (Vaccinium corymbosum L.) during storage
Full text linkBlueberry consumption increases because its health properties linked to antioxidants, easy cultivation and profitability. The ability to preserve fruits in controlled atmosphere (CA) allows extending the marketing calendar. The work evaluates parameters linked to the cellular redox state of blueberry fruits, cv. Brigitta, stored at 0°C at different atmosphere regimes (CA1= 10% CO2, 4% O2 and CA2= 9% CO2, 2% O2, compared to air as control). During storage, quality was assessed by the content of ascorbic acid (AA), antioxidant and index of fruit metabolic status, and of malondialdehyde (MDA), cell membranes oxidative stress and senescence marker; soluble solids content, titratable acidity and dry matter were also determined. Storage in CA increases the blueberries shelf life, particularly at the intermediate times; after 2 months there is a drastic lowering in AA levels and differences among treatments are no longer detectable. Ascorbate is confirmed to be an excellent index of oxidative stress in fruit senescence processes. In control, along with the AA decrease, there is a higher MDA content, in particular up to the intermediate dates. CA2 proves to be the most suitable atmosphere for delaying the senescence process. Titratable acidity and soluble solids remain constant in all samples throughout storage
Calcium and pectin influence on peach flesh texture
No full textThirty-four peach cultivars and seedlings were tested for firmness, skin background colour, TSS, ethylene production. In addition, total? soluble and insoluble pectins and both total and pectin-bound calcium were measured. Melting, non-melting, stony hard phenotypes were included and a possible novel "crispy" phenotype as well. Firmness was not related to flesh texture. While total pectin content did not determine firmness, both soluble and insoluble pectin were related to firmness. Stony hard phenotypes showed a very high content of calcium and total pectin. The "crispy" types had a very high level of calcium bound to insoluble pectins. This finding could possibly explain their textural features due to the allocation of calcium ions in cell walls. The relationship between pectins total and pectin-bound calcium seems to add an interesting field of research for defining objective methods for assessing flesh texture in peach
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