Investigation on Early Softening of Kiwi Fruit (original) (raw)
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Kiwifruit Softening: Comprehensive Research Approach in Chile and Relevant Results
VI International Symposium on Kiwifruit, 2007
Early softening is the main problem for the exports of Chilean kiwifruit. It has been related to orchard, harvest and postharvest factors. Therefore, a 4-year project is being carried out to study the problem comprehensively, to determine the main factors involved and the possibilities of predicting and controlling it. Experiments were carried out to determine the influence of growing conditions and the most important fruit characteristics on the softening rate of kiwifruit cultivated in different areas throughout Chile. Different postharvest handling techniques were evaluated to identify critical points along the entire production and postharvest chain. Fruit from all orchards were harvested at 6.2-6.5% soluble solids content (excepting fruit for maturity effects), and kept under the same storage condition (0°C, air). Samples were taken every fifteen days to determine softening propensity by measuring the number of days elapsing until fruit reached 18N firmness. Results so far indicate that softening behaviour of kiwifruit can be affected by light exposure, plant vigour and nutrition, fruit characteristics and position on the plant. Canopy management, water availability and Ca applications were also studied. Maintaining fruit firmness is assisted by vine management that ensures moderate vigour, adequate exposure of the plant and fruit to light, reduction of competition between fruit and vegetative growth and Ca applications to the fruit. Larger fruit size, time of harvest and position on the vine are also important characteristics. In addition, postharvest handling has been critically analysed and some limitations have been identified as a source of difficulties for Chilean kiwifruit that can be overcome through specific measures such as temperature management, controlled atmosphere and decay control, as well as control of ethylene. Using the results obtained a mathematical model to forecast early kiwifruit softening is being developed. This work was carried out within the FONDEF project Number D02I1058
A new descriptive method for fruit firmness changes with various softening patterns of kiwifruit
Postharvest Biology and Technology, 2013
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.
Food and Bioprocess Technology, 2013
The effect of heat pre-treatment (45°C/25 min), applied to whole fruit, and post-cut calcium dips in 1 and 2 g/L CaCl 2 solutions on respiration rate and texture preservation of kiwifruit slices was studied. During a 9-day period, packages' atmosphere composition, slices' firmness, pectin content and sensory scores were evaluated. Histological observations of samples were also performed. Neither heat pre-treatment nor calcium dips alone were effective in diminishing respiration rate of the slices but the application of both treatments revealed a synergistic effect on respiration rate reduction. Calcium-dipped fruit slices showed better firmness preservation. Post-cut calcium dips, alone or combined with heat pre-treatments, yielded slices presenting higher insoluble/total galacturonic acid ratio, indicating formation of calcium pectates. Slices from heat-pre-treated fruits, even in the absence of calcium, also revealed insoluble/total galacturonic acid ratio similar to calciumtreated slices, supporting, despite the lower firmness value, a more structured tissue, as observed in SEM microphotographs. Sensory and physical-chemical parameters obtained were correlated. The effectiveness of calcium treatment was equally observed for both tested concentrations during a 9-day shelf life period.
Fruit flesh firmness Fruit dry matter content Fruit load Kiwifruit storability Relationships between carbohydrates and organic acids Relationships among fruit qualitative characteristics a b s t r a c t Yield and fruit characteristics from nine orchards of the cultivar 'Hayward' were investigated in 2007-2008. The two-year average yield ranged from 24 t/ha to 49 t/ha. Yield was negatively related (P ≤ 0.01) to fruit dry matter content (DMC) and total titratable acidity (TTA) at harvest and total soluble solids (TSS) and flesh firmness after 5 months of storage. Fruit DMC at harvest was positively related to TSS (P ≤ 0.001) and flesh firmness (P ≤ 0.01) after 5 months of storage. At harvest, fruit DMC was also positively related (P ≤ 0.001) to non-structural carbohydrate content (glucose + fructose + sucrose + starch); moreover, the non-structural carbohydrate content was positively related (P ≤ 0.05) to TTA and citrate and malate contents. Fruit DMC at harvest was also positively related (P ≤ 0.05) to the content of structural material, estimated as the difference between DMC and the measured non-structural carbohydrates and titratable organic acids. The content of fruit structural material at harvest was positively related (P ≤ 0.05) to flesh firmness after 5 months of storage. After 5 months of storage, also the TSS was positively related (P ≤ 0.01) to the flesh firmness. Finally, there was a positive relationship (P ≤ 0.05) between fruit starch content and flesh firmness after 5 months of storage. The results showed that a very high fruit load can have negative effects on fruit DMC and TTA at harvest and TSS and flesh firmness after storage. Moreover, a higher DMC, besides being related with a higher TSS in ripe fruits, was also associated with a higher TTA and organic acids content and the retaining of higher flesh firmness during storage. This indicates that fruit DMC may be an indicator of both eating quality and storability of kiwifruits.
Modelling batch variability in softening of ‘Hayward’ kiwifruit from at-harvest maturity measures
Postharvest Biology and Technology, 2014
Firmness of kiwifruit (Actinidia deliciosa (A. Chev) C.F. Liang et A.R. Ferguson cv. Hayward) is an important determinant of quality. Batches of fruit vary not only in firmness at time of harvest but also in time to reach eating ripeness (0.5-1.0 kg f). Failure to identify batches with rapid rate of firmness breakdown results in economic loss to the industry. Understanding variability in softening rate and its relation with at-harvest measures may lead to opportunities for industry to segregate batches for storage potential. The objective of this paper was to model batch-specific softening behaviour of kiwifruit and investigate if predictive models could be determined from at-harvest maturity measures. Data for 'Hayward' kiwifruit softening at 20 • C were collected over 21 d for 108 batches across two seasons (2011 and 2012). In model creation, application of both Complementary Gompertz (CG) equation and a time shift (TSCG) alternative version resulted in a mean absolute error (MAE) of 0.11-1.55 kg f and 0.14-1.44 kg f respectively for 54 batches. Model parameters were fitted using a non-linear mixed effects procedure. The resulting batch-dependent softening description parameters (B, Ä and) were best associated with at-harvest firmness and the SSC:firmness ratio. For prediction validation, at-harvest quality indicators of an alternative set of 54 batches were used to predict softening descriptive model parameters and subsequent batch-dependent softening behaviour at 20 • C. When B and Ä were predicted from firmness and the SSC:firmness ratio respectively in the validation batches, MAE of firmness prediction by CG ranged from 0.17 to 2.75 kg f with 46% of the batches having MAE of less than 0.5 kg f. Likewise, when was predicted from firmness, MAE of firmness prediction by TSCG ranged from 0.17 to 2.78 kg f and approximately 30% of batches had MAE less than 0.5 kg f. This paper demonstrates the potential for predicting softening variability of kiwifruit batches from at-harvest fruit maturity measures. Future work is required to ascertain if a similar modelling protocol may enable prediction of kiwifruit softening at commercial storage conditions (0 • C).
Effects of maturity stage and mild heat treatments on quality of minimally processed kiwifruit
Journal of Food Engineering, 2006
A central composite rotatable experimental design was used on kiwifruits of two distinct maturity stages (firm ripe and soft ripe), subjected to mild heat pre-treatments by immersion during 10-90 min in water at temperatures of 25-50°C. Minimal processing of the fruits was performed 24 h after the heat treatment and soluble solid content, colour and texture properties were analysed in the samples during the whole storage period (0-10 days). For both maturity stages, the effect of heat treatment on colour was negligible. For fruits of the early maturity stage (firm ripe), total content of soluble solids increased with the mild heat pre-treatments. Pretreatments avoided texture breakdown in firm ripe kiwi slices. Firmness, the most sensitive parameter, is increased or preserved using treatment periods of up to 40 min. Favourable responses were evidenced immediately after them and during the whole storage period. Therefore, mild heat pre-treatments, when applied to firm ripe kiwi at temperatures below 45°C during less than 25 min improve the quality, mainly the firmness, colour being only marginally affected.
Maturity assessment at harvest and prediction of softening in an early and late
For peaches and nectarines, establishing fruit maturity at harvest is a crucial issue, since fruit shelf-life potential and quality are closely related to fruit maturity. A portable instrument that measures IAD (the index of absorbance difference between 670 and 720 nm) was used for monitoring the progression of ripening in two peach cultivars. IAD was measured at harvest in ‘Oded’ (an early season, fast melting flesh peach) and ‘September Snow’ (a late season, slow melting flesh peach) fruit. After harvest the fruit were divided into comparable lots and held at 20 ◦C. The IAD and firmness were measured daily on a different lot. Firmness decay during shelf-life was analyzed by non-linear regression, using the IAD measured at harvest to determine the maturity of the fruit and to estimate the biological shift factor (BSF) which is related to the biological age of fruit. A logistic model developed for firmness decay with maturity assessment by time-resolved reflectance spectroscopy was used, where the time-resolved measurement was substituted by IAD. The R2 for ‘Oded’ softening was 0.86, while that of ‘September Snow’ was 0.66. IAD decay was analyzed by non linear mixed effects analysis, obtaining Radj 2 higher than 0.96 for both cultivars. IAD showed the same decay rate in the two cultivars, while softening rate was five times lower in the late ‘September Snow’ than in the early ‘Oded’ fruit. The measurement of IAD at harvest could be used to separate fruit into different groups according to their potential shelf-life.
Postharvest performance of the yellow-fleshed ‘Hort16A’ kiwifruit in relation to fruit maturation
Postharvest Biology and Technology, 2014
Postharvest performance of fruit is dependent on the maturity or physiological state of the fruit at harvest in conjunction with the postharvest management applied. For yellow-fleshed kiwifruit, the flesh colour is a significant quality attribute, and for 'Hort16A', flesh colour has been used for timing harvest. Variability in the postharvest performance of 'Hort16A' kiwifruit suggests that flesh colour alone is not as strongly indicative of postharvest performance as soluble solids content (SSC) was found to be for 'Hayward' kiwifruit 30 years ago. The postharvest performance of 'Hort16A' kiwifruit, assessed as the fruit firmness and chilling injury expression during storage, has been associated with a range of fruit characteristics: flesh colour, SSC, firmness, seed colour, fresh weight, dry matter, starch and soluble carbohydrates measured at harvest throughout maturation. The changing responses of the fruit SSC to temperature, and softening to ethylene, have also been determined. The data illustrate the complex nature of 'Hort16A' fruit maturation, even when looking only at simple, easy-to-measure fruit attributes. While a yellow flesh colour is a commercial necessity for 'Hort16A' kiwifruit, flesh colour is not a robust indicator of postharvest performance and is not tightly linked to SSC or firmness. Changes in the capacity of fruit to respond to temperature or ethylene are not reflected in on-vine changes. Softening in storage is strongly linked to the softening rate occurring on the vine at the time of harvest. Any association between at-harvest characteristics and chilling susceptibility is less clear, and chilling tolerance appears more associated with the completion of growth and carbohydrate accumulation than with increased soluble solids accumulation rates as in 'Hayward'. Approaches to extend the understanding of the link between maturation, harvest indices and postharvest performance are discussed.
Journal of the American Society for Horticultural Science
Establishment of a controlled atmosphere (CA) of 2% O2 + 5% CO2 within one day of harvest (no delay) or after a one-week delay in 0°C air retarded rapid softening of CA-stored kiwifruit (Actinidia chinensis Planch. ‘Hayward’) during the 1st 6 weeks of 0° storage, relative to those kept in air or in CA established after a 2-week delay. Between the 6th and 24th week of storage, further softening in air-stored fruit was suppressed in all CA treatments, and the 2-week delay CA fruit always were significantly softer than those placed in CA within one day of harvest. The one-week delay treatment resulted in an intermediate flesh firmness. The rates of fruit softening at 0°-air after 12, 16, or 24 weeks of CA storage were comparable to those of fruit stored continuously in 0° air.
Fruit Growing Research
Kiwifruit is recognized as highly nutritious having many biochemical characteristics that deliver a range of health benefits. In Romania, kiwi is a new fruit species and the creation, testing and introduction of winter hardy genotypes, adapted to the local harsh climate conditions is a priority. A common Italian-Romanian kiwifruit breeding program was initiated in 1993 and during the time, several hybrid genotypes were obtained and introduced to be tested. After more than two decades of research, it was demonstrated that Actinidia deliciosa and Actinidia chinensis can be grown in Romania in peach favourable areas, while Actinidia arguta (hardy kiwi, kiwiberry) can cover larger areas, suitable for plum cultivation. At the Faculty of Horticulture within the University of Agronomic Sciences and Veterinary Medicine of Bucharest, an experimental field with kiwifruit hybrid genotypes, was established in 1993. The plants were grown under an organic orchard management, on a T-bar trellis, being irrigated with micro sprayers. The fruits were harvested at beginning of November, in 2017 and 2018. Harvesting moment was established when the fruit flesh firmness was lower than 7.0 kg force cm 2. After harvesting, kiwifruits were stored in two different cold storage conditions: normal atmosphere (NA) at 3°C and 95% humidity and controlled atmosphere (CA) with 1.5% Oxygen, at 1-2°C and 95% humidity. The aim of this study was to analyse the fruit quality characteristics of some new kiwi hybrid genotypes at harvest and during storage with the final goal to select best elites. Fruit weight and shape index have been determined after harvest. Different fruit characteristics were measured and evaluated in dynamics: firmness, soluble solids, dry matter, titratable acidity and ascorbic acid. All the determinations and analyses were made at the Research Center for Studies of Food Quality and Agricultural Products laboratories. During the storage, observations showed that R1P9 kiwifruit hybrid presented better biochemical quality parameters and the lowest weight losses compared to the other studied hybrids-4.69 % in CA and 5.22 % in NA. As expected, keeping kiwi fruits in controlled atmosphere with 1.5% Oxygen, at 1-2°C and 95% humidity, presented better physical and biochemical quality compared with those stored in normal atmosphere, at 3°C and 95% humidity. Using the results of the study regarding the fruits physicochemical characteristics after harvesting and during the storage, but also some other plant parameters, several kiwi hybrid elites were selected-R0P13 and R1P9. They will be propagated and planted for the production test. Cuvinte cheie: fermitate pulpă, substanţă uscată solubilă, substanţă uscată totală, aciditate titrabilă, acid ascorbic.