The fruit cuticle as a modulator of postharvest quality

The composition and structure of fruit surface tissues have a noticeable influence on the postharvest storage potential of fruit, inasmuch as they behave as a barrier against drying, chemical attack, mechanical injuries and microbial infection. The cuticle is made of cutin, a biological insoluble polyester, embedded in an impermeable wax complex, and its inner side interacts intimately with the underlying epidermal cell walls. The cuticle plays a decisive role in plant development, being the first communication system with the surrounding biotic and abiotic environment. Published reports on the composition and biosynthesis of fruit cuticles are comparatively scarce, and many knowledge gaps exist on the part cuticles play in quality determination and postharvest performance. This review aims at collecting available information in relation to the role of the fruit cuticle as a determinant factor of some important traits related to postharvest quality, including water loss, susceptibility to physical and biological stresses, and decreased fruit firmness. To the best of our knowledge, this is the first published work focusing on the fruit cuticle as a major modulator of postharvest quality and interlinking existing dispersed literature on this topic. A deeper understanding of cuticle structure and function will be of help in understanding postharvest biology and in designing new technological solutions.     

Influence of exogenous ethylene during refrigerated storage on storability and quality of Actinidia chinensis (cv. Hort16A)

The kiwifruit industry was established on fruit of Actinidia deliciosa (‘Hayward’), which is known as a climacteric fruit with high sensitivity to ethylene. In recent times fruit from Actinidia chinensis have become a substantial component of the kiwifruit market. There is limited information about the sensitivity of A. chinensis to ethylene during refrigerated storage and hence current ethylene management practices for A. chinensis mimic those established for A. deliciosa. This research aimed to quantify the effect of ethylene during refrigerated storage on A. chinensis (‘Hort16A’) quality (firmness, colour and total soluble solids). Three grower lines were stored at 1.5 °C, 95% RH with ethylene in the range of 0.001-1 μL L⁻¹ applied to the environment after 3 weeks of storage for the remainder of storage (17 weeks). Fruit quality was assessed at regular intervals. Loss of firmness was found to be very sensitive to ethylene, with significant differences between fruit stored in 0.001 μL L⁻¹ (as a control) and 0.1 μL L⁻¹ occurring after 2 weeks of exposure. Fruit exposed to 1 μL L⁻¹ ethylene not only rapidly softened, but also increased in hue angle (greenness) and reduced in lightness (darkened) further reducing the quality of the yellow coloured kiwifruit cultivar. Total soluble solids were not heavily influenced by ethylene exposure, with grower differences being maintained throughout the experiment. This work demonstrates that A. chinensis (cv. Hort16A) fruit firmness and colour will be influenced by the ethylene conditions in a commercial storage environment by advancing ripening and senescence.     

Benzyl-aminopurine (BAP) treatments delay cell wall degradation and softening,improving quality maintenance of refrigerated summer squash

Round summer squash are harvested before reaching full maturity and even though they are highly perishable, fruit postharvest handling is mostly based on storage at non-chilling temperatures. Finding complementary treatments minimizing deterioration and reducing postharvest losses would be extremely useful. In this work we evaluated the effect of postharvest cytokinin (CK) treatments on refrigerated round soft rind squash. Fruit were harvested at commercial maturity and sprayed with 1 mmol L⁻¹ benzylaminopurine (BAP) or water (control) prior to storage at 5 °C for 0, 13 or 25 days. Quality was assessed upon removal from cold storage as well as after a 2 day shelf-life period at 20 °C. CK-treated fruit showed slower deterioration and dehydration and remained firmer than the control. BAP sprays did not affect color, respiration or sugar-acid balance. The treatments prevented phenolic compound accumulation, and decreased pectin solubilization. By the end of the storage period BAP-treated squash had higher levels (45%) of tightly-bound polyuronides than untreated controls, indicating a substantial delay in cell wall dismantling. CK sprays also reduced neutral sugar solubilization from pectin-rich fractions, but no changes were found in the cross-linking glycans or cellulose. To our knowledge, this is the first work showing that CK can regulate pectin disassembly in developing fruit. Postharvest BAP sprays preventing texture deterioration may be a simple treatment to complement refrigeration of round, soft rind, summer squash.     

Anaerobic metabolism during short and long term storage of kiwifruit

Kiwifruit were stored in 0.25% O₂ (ULO), 1% O₂ (LO) and 2% O₂ + 5% CO₂ (CA) and the controls were kept in air. The fruit were held at 0 °C for 34 and 94 d of storage and, after these times, were transferred to 20 °C in air for 14 d of shelf life. During the short term storage (34 d), a significant increase in anaerobic metabolites, above all ethanol, was observed in ULO, LO, and CA fruit (166, 131, 120 μL/L). After the shift to shelf life, a large and unexpected increase in PDC (pyruvate decarboxylase), ADH (alcohol dehydrogenase in the direction of ethanol oxidation), LDH (lactate dehydrogenase), and GPT (glutamate-pyruvate transaminase) was observed, resulting in ethanol depletion (ULO) or no further increase, and an increase in acetaldehyde which, in turn, could have hastened fruit ripening. Even the control fruit showed an increase in ethanol during storage and an increase in enzyme activity during shelf life, especially in ADH, but to a lesser extent without an increase in acetaldehyde. During the long term storage, anaerobic metabolites (ethanol and acetaldehyde) still increased and GPT activity rose significantly in the ULO and CA samples. A burst of enzyme activity was also observed during the second shelf life in the CA and LO samples, but not in the control, while in ULO fruit the activity rose continuously. GPT activity showed the highest peaks in CA and ULO fruit. An ethylene burst was observed in ULO and CA fruit during the second shelf life (about 25 μL/kg-h) but not during the first shelf life. The potential role of these enzymes in kiwifruit stress response during storage and shelf life is discussed.     

Regulation of propylene-induced ripening and ethylene biosynthesis by oxygen in ‘Hayward’ kiwifruit

Kiwifruit, cv Hayward, were treated with 130 μl/l propylene under 1, 5, 10, 13, 16, and 21% O₂ concentrations in a continuous flow-through system at 20 °C. Control kiwifruit were kept in air (21%O₂). Flesh firmness, soluble solids content, internal ethylene concentration, l-aminocyclopropane-l-carboxylic acid concentration (ACC), malonyl-l-aminocyclopropane-l-carboxylic acid concentration (MACC), and EFE capacity were measured during the experiment. Ethylene biosynthesis and fruit ripening were stimulated when kiwifruit were exposed to a mixture of propylene in 21% O₂. Reduction of oxygen concentration (< 10%) inhibited the effectiveness of propylene on autocatalytic ethylene production possibly through a reduction in ACC concentration in the tissue. Exposure of kiwifruit to low oxygen concentrations (< 5%) delayed propylene-induced fruit ripening.     

A new descriptive method for fruit firmness changes with various softening patterns of kiwifruit

We have proposed a new interpretation of fruit softening. This was accomplished by generating a hypothesis that probabilities of decay of fruit structure obey the Weibull probabilistic model that has been used in the field of reliability engineering. The elasticity of individual kiwifruit after harvest was continually and nondestructively measured until decomposition by using a laser Doppler vibrometer. The obtained decreasing pattern of elasticity of individual fruit was complex, diverse, and inhomogeneous. Nonetheless, it was satisfactorily explained by a tandem combination of 2 Weibull models involving 4 types of parameters: “shape” related to probability; “scale,” to velocity of decay; “location,” to time lag; and “mixing ratio,” to contribution of the 2 models. Averages of location, shape, and mixing ratio parameters obtained by the measurement of 33 fruit were significantly different between the 2 models, but the scale parameter was not. The results suggested that the complex softening patterns of individual kiwifruit could be described using the tandem model of Weibull distribution, and that the softening process of kiwifruit consisted of at least 2 independent decay phases that are characterized by 2 of 5 parameters: location and mixing ratio. Commencement of the first decay phase could be caused by ethylene treatment after harvest, and the second one spontaneously triggered after a certain time lag.     

Effect of high temperature stress on ethylene biosynthesis, respiration and ripening of ‘Hayward’ kiwifruit

Temperatures up to 35°C have been shown to increase ethylene production and ripening of propylene-treated kiwifruit (Stavroulakis, G., Sfakiotakis, E.M., 1993. We attempted to study the regulation by high stress temperature of the propylene induced ethylene biosynthesis and ripening in ‘Hayward’ kiwifruit. ‘Hayward’ kiwifruit were treated with 130 μl/l propylene at temperatures from 30 to 45°C up to 120 h. Ethylene biosynthesis pathway and fruit ripening were investigated. Propylene induced normal ripening of kiwifruit at 30–34°C. Fruit failed to ripe normally at 38°C and above 40°C ripening was inhibited. Propylene induced autocatalytic ethylene production after a lag period of 24 h at 30–34°C. Ethylene production was drastically reduced at 38°C and almost nil at 40°C. The 1-aminocyclopropane-1-carboxylic acid (ACC) content was similar at 30–38°C and was very low at 40°C. The 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) activities decreased with a temperature increase above 30°C, but ACC oxidase decreased at a faster rate than ACC synthase. Fruit not treated with propylene showed no ripening response or ethylene production. However, kiwifruit respiration rate increased with temperature up to 45°C, reaching the respiration peak in 10 h. At temperatures up to 38°C, propylene treatment enhanced the respiration rate. After 48 h at 45°C, fruit showed injury symptoms and a larger decrease in CO₂. The results suggest that high temperature stress inhibits ripening by inhibiting ethylene production and sensitivity while respiration proceeds until the breakdown of tissues.     

一株抗猕猴桃溃疡病的芽孢杆菌分离和筛选研究初报

从猕猴桃根际土壤中分离到的115株芽孢杆菌中,经过皿内拮抗活性试验筛选到12株对猕猴桃细菌性溃疡病有较好抑制效果菌株。进一步单胞分离纯化后,拮抗活性明显增强,尤以B17-4、B56-1和B56-3效果显著。田间药效试验表明：B56-3菌株发酵滤液稀释500倍时,采用刮除病斑涂抹法防治效果达到88%。     

The need for characterisation and evaluation of germplasm: kiwifruit as an example

Genetic diversity provides the raw material for breeding and plant improvement. Breeders of plant species that have little or no history of improvement tend to make the greatest use of collections of raw or unimproved germplasm. Kiwifruit (Actinidia) are one such crop in that they have been subjected to little selection pressure and are still very similar to plants in the wild. To take advantage of the diversity in the genus Actinidia, breeders need to know the extent of the diversity and also need to be able to identify the plants with which they are working. Voucher specimens should be prepared for all plants used in experimental studies. A good understanding of the reproductive biology of Actinidia should facilitate incorporation of wild germplasm into kiwifruit breeding programmes. The HortResearch Actinidia collection has already proved its worth with the development of valuable new kiwifruit cultivars.     

Flower and fruit characters in a kiwifruit hermaphrodite

The dioecious genus Actinidia includes the kiwifruit, A. deliciosa. Currently, the kiwifruit industry is based predominantly on a single female cultivar, 'Hayward', with up to 13% of the orchard canopy in commercial blocks in New Zealand consisting of unfruitful males vines, necessary as pollinizers. The development of hermaphrodite cultivars became a possibility with the identification of inconstant males, which carry a mixture of staminate flowers and bisexual flowers, the latter developing into small fruits containing seeds. This paper describes a hermaphrodite vine, obtained as a rare variant among the progeny from a cross between 'Hayward' and an inconstant (fruiting) male. Testing of pollen from all flowers in one season and measurement of fruit characters after self-setting demonstrated this seedling is completely hermaphroditic, carrying only bisexual flowers, with no restriction on selfing. Although it does not have commercial potential, it will be used as a parent. Perceived benefits from the development of hermaphrodite cultivars include increased productivity, improved pollination, simplified vine management and therefore substantial cost savings. This revised version was published online in July 2006 with corrections to the Cover Date.     

生育期猕猴桃果实中营养元素积累规律研究

以秦美猕猴桃为试材,研究了猕猴桃果实生育期的干物质和N、P、K、Ca、Mg等大量元素及Zn、Cu、Fe、Mn等微量元素的积累规律。结果表明：在果实发育的整个过程都有干物质的不断积累,但不同时期其积累量和积累强度不同;大量元素中除Ca在果实中稳定积累之外,N、P、K、Mg均在夏季出现负积累而且起伏较大;微量元素中,果实吸Fe最多,但在7月之后就不断“流失”,Zn、Mn也较类似,Cu的吸收比较稳定。新梢生长对果实积累营养元素影响较大。     

Effects of new packaging solutions on physico-chemical,nutritional and aromatic characteristics of red raspberries (Rubus idaeus L.) in postharvest storage

Postharvest life of raspberries (Rubus idaeus L.) is limited due to their high respiration rate, loss of firmness and freshness and susceptibility to fruit rot. The aim of this research was to evaluate the effects of various packaging solutions on physico-chemical, nutritional and aromatic properties of raspberries during storage at +4 °C up to 7 days. Plastic materials with low (LDPE) and high (LDPE/EVOH/LDPE) gas barrier, a biopolymeric film (PLA) with medium gas barrier and micro perforated stretch film (PVC) were used. The packaging material modified the composition of the atmosphere in the package, which depended on the combined action of the respiration activity of the fruit and the permeability of the material. Results showed that the most sensitive parameters for the assessment of raspberry decay were percentage of damaged berries, weight loss, fruit softening and the aromatic profile development, evaluated by an electronic nose; these parameters showed significant changes during storage and were influenced by the packing material. All samples showed a clear loss of firmness after 4 days of storage, which was maximally reduced in the case of LDPE/EVOH/LDPE and PLA packages. Raspberries stored in PVC packaging material had an aromatic development similar to the control, whereas berries stored in the medium and high barrier materials showed important changes in the aromatic profile, reflecting anaerobic metabolism of fruit. Soluble solids, pH, total phenolics and ascorbic acid did not change significantly; changes in colour and total anthocyanins were observed, with differences depending on the kind of packaging.     

江西省保护性耕作的现状与分析

江西省位于中国的东南部，长江中下游交接处的南岸，水资源非常丰富，因此对保护性耕作的研究较少，虽然曾经推广过该项技术但由于技术集成度不高，再加上农民的认识不够等原因，使得目前的推广面积并不大。所以有必要对全省保护性耕作的现状进行调查、分析，并进行科学的试验示范，筛选出适合本地应用和发展的保护性耕作技术，因地制宜的逐步推广应用。     

四川盆周山区发展特色优质猕猴桃的优势与对策

通过对四川盆周山区发展特色优质猕猴桃的国际市场前景、生产现状、条件优势分析,提出了相应的对策和建议：发挥品种资源优势,推行规范化的综合配套生产技术;培育龙头企业,创立优势品牌;搞好产业结构调整,发展新兴生态产业。     

Relationship between browning and related enzymes (PAL, PPO and POD) in rambutan fruit (Nephelium lappaceum Linn.) cvs. Rongrien and See-Chompoo

Rambutan (Nephelium lappaceum Linn.) fruit cvs. Rongrien and See-Chompoo were stored in low (60–70%) and high (85–95%) relative humidity (RH) environments at 25 °C for 6 d. Changes in weight loss, browning index, phenols content and activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) were measured. By d 6 of storage, browning was severe in the spinterns but slight in the peel of both cultivars. High RH delayed spintern browning but had only a small effect on peel browning. The phenols content and PAL activity in peel from both cultivars were generally higher than in the spinterns. RH had no effect on the changes in phenols during storage but PAL activity increased in the peel but not spinterns of both cultivars at d 4 of storage in low RH. The initial activities of PPO and POD in spinterns of both cultivars were higher than in peel. PPO activity in the spinterns of both cultivars was similar and was not affected by RH. The initial activity of POD was lower in the peel and the spinterns of Rongrien fruit but there were no clear responses to RH during storage. Higher activities of PPO and POD in the spinterns compared to the peel may also be a factor in the higher rates of browning of the spinterns.     

Preharvest application of methyl jasmonate (MeJA) in two plum cultivars. 2. Improvement of fruit quality and antioxidant systems during postharvest storage

‘Black Splendor’ (BS) and ‘Royal Rosa’ (RR) plums were treated preharvest with methyl jasmonate (MeJA) at three concentrations (0.5, 1.0 and 2.0 mM) along the on-tree fruit development: 63, 77 and 98 days after full blossom (DAFB). Both control and treated fruit were harvested at the commercial ripening stage and stored in two temperature conditions: 9 days at 20 °C or at 2 °C + 1 day at 20 °C for 50 days. Preharvest MeJA at 2.0 mM significantly accelerated whereas 0.5 mM delayed the postharvest ripening process for both cultivars, since ethylene production, respiration rate and softening were reduced significantly at the two storage conditions for 0.5 mM. In these fruit, total phenolics, total antioxidant activity (hydrophilic fraction, HTAA) and the antioxidant enzymes peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were found at higher levels in treated than control plums during postharvest storage, which could account for the delay of the postharvest ripening process and the extension of shelf-life.     

中宁圆枣果实发育成熟期生理生化变化

以10年生的中宁圆枣为试材,研究了果实发育后期(白熟期￣全红期)生理和生化变化特性,结果表明:(1)中宁圆枣果肉硬度变化具有明显的2个阶段,从白熟期至初红期,果肉硬度大幅度降低;从初红期至全红期,硬度维持在12.0￣12.5kg/cm2。(2)果实抗坏血酸含量与果实发育成熟度呈极显著的负相关关系,相关系数r=-0.9686;果实可滴定酸含量与果实发育成熟度呈极显著的正相关关系,相关系数r=0.9254。(3)果实发育成熟期,可溶性固形物、总糖、蔗糖和果糖含量均与果实发育成熟度呈极显著的正相关关系,葡萄糖含量和果实发育成熟度呈显著的正相关关系。(4)中宁圆枣果实在白熟期前以积累单糖为主,果实糖份累积总体表现为“果糖 蔗糖”型。(5)随着果实发育成熟,果实相对甜度不断增加。果实总糖、可溶性固形物、蔗糖和果糖含量与果实相对甜度呈极显著正相关关系,相关系数分别为0.9940、0.9827、0.9750和0.9259;葡萄糖含量和果实相对甜度呈显著正相关关系,相关系数r=0.9117。     

1994-2004年猕猴桃专业研究文献计量分析

猕猴桃是中国原生果树树种之一,分布有62个种,占世界猕猴桃属植物66个种的93.9%,种质资源极为丰富。历史上仅限于采集野生果实、做中药材和观赏用。经济栽培起始于20世纪60年代末,生产栽培和专业研究发展迅速。经对1994—2004年专业期刊公开发表的猕猴桃专业文献进行计量分析,总文献量为1687篇,其中署名文献1502篇。第一作者814人,主要作者群为各类院校的教学科研人员,发表论文占论文总数的44.45%。确定了39位核心作者、11种核心期刊。     

Relationship of IAD index to internal quality attributes of apples treated with 1-methylcyclopropene and stored in air or controlled atmospheres

The research was conducted to evaluate the relationship between I_AD index (index of absorption difference between 670 and 720 nm) values and internal quality attributes of apples treated with 1-methylcyclopropene (1-MCP) and stored in air and controlled atmospheres (CA). Apples of ‘8S6923’ (Aurora Golden Gala™), ‘Fuji’ and ‘Royal Gala’ were tested. The results with Aurora Golden Gala™ show that I_AD index values were maintained at higher levels if the fruit were stored in CA and that 1-MCP had no significant effect on retaining at-harvest values. The I_AD values correlated with chlorophyll a content in the peel (R² = 0.95, P < 0.0001), but not with chlorophyll b content, internal ethylene levels, firmness or titratable acidity. ‘Royal Gala’ apples showed a similar response to Aurora Golden Gala™ apples, showing no correlation between I_AD index values and internal quality attributes of those apples when treated with 1-MCP and/or CA. In contrast, ‘Fuji’ apples showed a relationship between I_AD index value changes and internal ethylene concentrations (R² = 0.67, P < 0.05) and titratable acidity changes (R² = 0.89, P < 0.01), but not firmness. These results suggest that when 1-MCP and/or CA are applied to apples after harvest, that I_AD index values do not consistently correlate to any internal quality attributes other than peel chlorophyll a content.