Streif Index Research Articles

Impact of selenium fertilisation of ‘Red Jonaprince’ apple trees on selenium nutrition and fruit quality and storability

Selenium (Se) malnutrition in humans is caused by low soil Se availability, leading to an insufficient content of this nutrient in food. In this study, we examined the effect of Se fertilisation on the absorption and distribution of Se in apple (Malus domestica Borkh.) trees, as well as fruit quality and storability. The experiment was carried out on mature ‘Red Jonaprince’ apple trees grown in medium-textured soil. Fertilisation of Se (as sodium selenate) was applied as: (i) summer sprays, 4 times in a season at a rate of 50 g Se ha−1, (ii) a fall spray, 2 weeks before harvest at a rate of 200 g Se ha−1, (iii) soil application at a rate of 500 g Se ha−1, and (iv) fertigation at a rate of 100 g Se ha−1. Trees that were not fertilised with Se served as controls. The results revealed that the fall Se spray caused leaf burns and defoliation, but it did not affect tree vigour and fruit yield. The highest leaf Se concentration was found on Se-sprayed trees in the fall. Most Se in fruit was recorded on Se-sprayed trees in the fall and on Se-fertigated trees; fruit Se amounts from these combinations covered about 30 % of the recommended daily intake. None of the Se treatments affected fruit appearance (mean weight, skin russeting, and colour), flesh firmness, and acidity at harvest. Apart from the fall Se spray, the other treatments decreased the soluble solid concentration (SSC), starch index values, ethylene evolution, and increased Streif index values in apples at harvest. After storage, Se-enriched apples were firmer, contained more organic acids, and produced less ethylene than the control fruit. We conclude that Se fertigation or a fall Se spray can be recommended in apple orchards, at least for late season and winter varieties, to biofortify fruit with Se and delay their ripening process.

A flight sensing detector for apple maturity indexes in orchard

Apples quality monitoring and maturity measurement are important for yield evaluation, profit estimation, determination of harvest time and postharvest storage conditions. This study explored the monitoring ability of the micro-Unmanned Aerial Vehicle (UAV) to the orchard, the force sensor and gyroscope are used to observe the force and posture changes of apples during the spectral collection process. The UAV carries 18 channels of visible/near-infrared multispectral sensor to collect the internal information of growing apples at close range. A total of 200 apples were collected in the orchard, and then soluble solid content (SSC), titratable acid (TA), firmness, and starch pattern index (SPI) were destructively tested. Multiple scatter correction (MSC) and Standard normal variate (SNV) pretreatment combined with partial least squares regression (PLSR) were used to establish the internal quality prediction model. Streif index is used to evaluate the maturity of apples. The results showed that the detection of apples on trees by UAV would not affect the growth of apples and could collect the internal quality information. The correlation coefficient of the prediction model for apple maturity is 0.8593 and root mean square error is 0.0102. It shows that this study has potential in detecting the changes of quality and maturity of growing apples and is helpful to the overall perception of orchards.

Non-destructive and in-site estimation of apple quality and maturity by hyperspectral imaging

• Hyperspectral imaging monitored the quality of apple directly in orchards. • Relative spectral processing could reduce the unevenness of ambient light. • The accuracy of the prediction models met the requirements of orchard management. • The dynamic process of apple quality and maturity was visualized. Rapid and in-situ estimation of apple quality and maturity is of great significance to guarantee the quality of apples and the profit of the industry. This study explored the utility of hyperspectral imaging (HSI) in assessing the quality and maturity of apples. Hyperspectral images, in the range of 500–900 nm, were collected directly in the orchard. A total of 100 apples contained in the visual field of the camera were picked for destructive testing of firmness, soluble solids content (SSC) and starch pattern index (SPI). To reduce the complicated outdoor light interference, we adopted the PTEE ball as the white reference. Normalized reflectance spectrum (NR) and normalization different spectral index (NDSI) involving all possible two-band combinations were also extracted for apple quality estimation. Subsequently, partial least squares regression (PLSR) analyses were conducted using the characteristic wavelengths extracted by stability competitive adaptive reweighted sampling (SCARS). The PLSR model established by NDSI combined with SCARS achieved the best results. The correlation coefficient of validation set ( R v) of firmness, SSC and SPI were 0.783, 0.901 and 0.834, respectively. The root-mean-square errors of the validation set ( RMSEv ) of firmness, SSC, SPI were 0.993 kg/cm 2 , 0.535% and 0.427, respectively. The Streif index was used to evaluate the maturity of apples, which was calculated from the predicted value of firmness, SSC and SPI. The RMSEv of the PLS model for Streif index was 0.0120. The results indicated the potential of the NDSI-SCARS-PLSR model based on hyperspectral imaging to observe the dynamic changes in the quality and maturity of the apples in site. This model could provide the spatial distribution of apple quality and maturity, which would be valuable for exploring the maturation pattern, grasping the growth of the area, and planning harvest time.

Review on postharvest quality and handling of apple

Apple is a climacteric temperate fruit with high market demand providing essential components to the body. Nowadays, apple production is increasing every year especially in EU member countries are the highest producer. Hence, this paper reviews the postharvest quality and associated changes during handling. Usually, farmers face difficulty in estimating the right harvesting time though Different methods exist to test the maturity stage such as counting the days after full bloom, color change, firmness test, measuring soluble sugar, starch iodine test and Streif index. Depending on different factors, farmers can choose the best maturity estimation method in various locations. Postharvest diseases of apples makeup a major part of the economic losses incurred during apple production. Annual losses of many fruits, including apple, vary from 5 to 35% and for developing countries, it ranges between 20%-50%. The most common causes are poor harvesting methods, transportation and storage methods which can open access for fungal growth species such as Botrytis species. B. cinerea is one of the most important of the species with unique characteristics causing the highest losses.

Apple Fruit Growth and Quality Depend on the Position in Tree Canopy.

Modern apple orchard systems should guarantee homogeneity of fruit internal and external qualities and fruit maturity parameters. However, when orchards reach productive age, a variation of these parameters takes place and mostly it is related to uneven light distribution within the tree canopy. The aim of the study was to evaluate the canopy position’s effect on fruit internal and external quality parameters. This is the first study where all the main fruit quality and maturation parameters were evaluated on the same trees and were related to the light conditions and photosynthetic parameters. Four fruit positions were tested: top of the apple tree, lower inside part of the canopy, and east and west sides of the apple tree. Fruit quality variability was significant for fruit size, blush, colour indices, total sugar content, dry matter concentration, accumulation of secondary metabolites and radical scavenging activity. Fruit position in the canopy did not affect flesh firmness and fruit maturity parameters such as the starch index, Streif index and respiration rate. At the Lithuanian geographical location (55°60′ N), significantly, the highest fruit quality was achieved at the top of the apple tree. The tendency was established that apple fruits from the west side of the canopy have better fruit quality than from the east side and it could be related to better light conditions at the west side of the tree. Inside the canopy, fruits were distinguished only by the higher accumulation of triterpenic compounds and higher content of malic acid. Light is a main factor of fruit quality variation, thus all orchard management practices, including narrow two-dimensional tree canopies and reflecting ground covers which improve light penetration through the tree canopy, should be applied.

Analysis of Possibility to Apply Preharvest 1-Methylcyclopropene (1-MCP) Treatment to Delay Harvesting of Red Jonaprince Apples

The production of Red Jonaprince cultivar is increasing, but the quality of apples is still challenging. Therefore, various options may be used including 1-Methylcyclopropene (1-MCP) application, as it influences ethylene receptors and blocks them, resulting in the possibility of delaying harvesting. The preharvest application of 1-MCP has not been studied so far for this cultivar but for other ones it has been successful, as it is based on the understanding of the natural apple ripening process. The study aimed to analyze the possibility of applying a 1-MCP treatment in the preharvest period for Red Jonaprince apples. The study was conducted based on a comparison of apples from two groups of Red Jonaprince apple trees (4 years) cultivated in an experimental orchard, where for one of them 1-MCP was applied in the preharvest period (HarvistaTM; 150 g per ha; 20 September—12 days before the optimum harvesting window (OHW)). For both groups, the apples were studied twice, for harvesting in the OHW (2 October) and for delayed harvesting (24 October). The harvested fruits were stored in an Ultra Low Oxygen chamber (ULO; 1.2% CO2, 1.2% O2) until May. They were analyzed before storage (preharvest) five times (20 September–24 October) and after storage (postharvest) three times (20 March–18 May). The following parameters were included: firmness, total soluble solids (TSS) content, titratable acidity (TA). For the preharvest period, the parameters also included internal ethylene content (IEC), starch index, and Streif index. For the preharvest period, significant differences associated with the 1-MCP treatment (p ≤ 0.05) were observed for the IEC (lower results for apples treated for 4th and 5th assessment), TA (higher results), and Streif index (higher results). Meanwhile, for firmness, TSS, and starch index for the majority of measurements there were no differences (p > 0.05). For the postharvest period, significant differences associated with 1-MCP treatment (p ≤ 0.05) were observed for firmness (higher results) and TA (higher results) both for OHW and delayed harvesting. It was concluded that a preharvest 1-MCP treatment allowed delayed harvesting and reduced the quality deterioration during the ULO storage of Red Jonaprince apples.

Effects of molybdenum sprays on the growth, yield and fruit quality of ‘Red Jonaprince’ apple trees

The aim of the study was to examine the responses of mature ‘Red Jonaprince’ apple (Malus domestica Borkh.) trees/M.26 to molybdenum (Mo) sprays. The experiment was conducted in Central Poland in 2017-2018 at high-density orchard growing on strongly acidified coarse-textured soil with low Mo availability. Trees were sprayed with Mo in the form of sodium molybdate before bloom (at pink bud), at bloom (when 5-20% of flowers were open) or after bloom (14 days after petal fall). In each spray, the Mo rate was 286 g ha-1. Trees that were not treated with Mo served as the control. Except for manganese (Mn), the concentrations of the essential macro- and micronutrients in the summer leaves of the control trees were within optimum/sufficient ranges. The summer leaf Mn concentrations were high but not toxic. Prebloom and bloom Mo sprays increased the activity of nitrate reductase (NR) and SPAD chlorophylometer values for leaves at 21 days after full bloom (DAFB), Mo concentrations in flowers and seeds, the number of seeds in an apple, fruit Ca concentration (on average by 23% for both Mo spray treatments), and the Streif index values of the fruit at harvest. The postbloom Mo spray increased the summer leaf concentrations of nitrogen, magnesium, iron and Mo, and the NR activity and SPAD values of leaves at 21 DAFB and at harvest. No Mo spray affected tree vigour, fruit set and yield, mean fruit weight, skin russeting and blushing, and the soluble solids concentration and flesh firmness of apples at harvest. It is concluded that when the apple flower Mo concentration, at least in triploid varieties, is as low as 1.5 mg kg-1 DW, a prebloom or bloom Mo spray is recommended to improve Ca-related apple quality.

The Effects of Preharvest 1-Methylcyclopropene (1-MCP) Treatment on the Fruit Quality Parameters of Cold-Stored ‘Szampion’ Cultivar Apples

Postharvest treatment by 1-methylcyclopropene (1-MCP) for ‘Szampion’ cultivar apples inhibits ripening of climacteric fruit by blocking ethylene receptors, preventing ethylene from binding and eliciting its action. It is also possible to apply 1-MCP preharvest, which so far has not been studied for the ‘Szampion’ cultivar. The aim of this study was to assess the effects of preharvest 1-MCP treatment on the fruit quality parameters of cold-stored ‘Szampion’ cultivar apples in a Polish experiment. Two identical groups of apple trees (6 years, experimental orchard in Warsaw) were included, to obtain studied apples (preharvest 1-MCP treatment with HarvistaTM, 150 g/ha, 7 days before the optimum harvesting window, OHW) and control apples (1-MCP not applied). Apples for the studied group were harvested twice—on 28 September (OHW) and 24 October (delayed harvesting)—and for control group once—on 28 September, as before 24 October the majority of apples fell from trees. Afterwards, apples were stored in an Ultra Low Oxygen chamber (1.2% CO2, 1.2% O2). Apples were assessed in the preharvest period (weekly, six measurements for the studied group, and five measurements for the control group) and postharvest period (monthly, three measurements separately for each harvest time for the studied group and control group). The following parameters were assessed: internal ethylene content (IEC), firmness, total soluble solids (TSS) content, starch index, Streif index, titratable acidity (TA), and color for blush. For the preharvest period, statistically significant differences between the studied group and the control group were observed for IEC, the a* coordinate of color (p < 0.05; for apples treated with 1-MCP lower results), firmness, Streif index, TA (p < 0.05; higher results), and starch index (p < 0.05; no defined trend). For the postharvest period, statistically significant differences between the studied group and the control group were observed for apples harvested in the OHW for firmness (p < 0.05; for apples treated with 1-MCP higher results) and IEC (p < 0.05; no defined trend), while for delayed harvesting the differences were only minor. It may be concluded, that preharvest 1-MCP application makes it possible not only to obtain better results for ‘Szampion’ cultivar apples’ quality parameters, but also allows delayed harvesting without deterioration in quality.

Comparative characteristics of some complex indicators of the degree of apple fruit maturity in determining the technical degree of maturity for juice

Currently, there are no direct methods for determining the degree of fruit maturity, and researchers use complex indicators that take into account several parameters. The purpose of our work was to give comparative characteristic to some complex indicators of apple fruit maturity when determining technical degree of a maturity for juice and to define the most reliable. The article presents data of the comparative study of integrated indicators of the degree of apple fruit maturity - Strerf index, Yager index and FARS index, which was conducted on 11 apple varieties breeding in the All-Russian Research Institute of Fruit Crops Breeding when determining the technical maturity for juice. The studied apple varieties were of various terms of maturing, immune to scab and included in the State register of breeding achievements admitted for use. As control variety was used the Antonovka Obyknovennaya, everywhere widespread in fruit plantations and widely used in processing. When calculating Streif index, Yager index and FARS index we used the following parameters: firmness (density) of pulp, starch-iodine index, total soluble solids, total titratable acidity. It has been found that the Streif index and FARS index in most varieties had the same value (0.1) at the maximum juice yield, characterizing the optimal technical degree of maturity for the juice. The Yager index was characterized by high lability of the values of optimal technical degree of fruit maturity for juice - on the average, from 1.2 in ‘Veniaminovskoye’ and to 3.9 in ‘Orlovim’ varieties. The average values of the Streif index, Yager index and FARS index during the studies were 0.12, 2.12 and 0.10, respectively. On the basis of the obtained data, the most reliable indicators of the technical degree of maturity of apple fruit for juice should be considered complex indicators of fruit maturity: the Streif index (0.10) and FARS index (0.10).

PA and DA meter – providers of the new ripeness index?

New ripening instrumentation like the PA analyser and the DA meter offer non-invasive tools based on degradation of chlorophyll in the fruit peel; their values were compared with the Streif index measured by an ART system, as traditional ripeness viz., picking tool using 5-year-old 'Braeburn Hillwell' at Klein-Altendorf in autumn 2015, when environmental weather pattern delayed harvest by ca. 3 weeks. Treatments included two reflective mulches and two biostimulants with an untreated control. The study showed that: 1) DA meter values (IAD) gave consistent results for the four treatments at the six measuring dates before harvest; 2) DA meter values (IAD) highly correlated with r=0.84-0.94 with Streif indices (ART system); 3) when 'Braeburn' stopped ripening at Streif=0.18 (harvest window for Streif 0.25-0.14 and for starch 3-5), DA meter values still continued to decrease; 4) fruit with reflective mulch (Extenday) appeared earlier ripe with the DA meter but later ripe with the ART system; 5) if we start to manipulate ripening e.g., by chemicals (phosphates, biostimulants, reflective mulches, 1-MCP), Streif values may reflect those changes in ripening, whereas DA meter values (IAD) still continue to decline at the same rate, unless the treatment has a direct chlorophyll effect, where DA values may be tricky to use.

Effect of non-chemical crop load regulation on apple fruit quality, assessed by the DA-meter

Abstract The objective of the present work was to investigate alternatives to chemical crop load management (CLM) for cv. ‘Gala Mondial’ to improve fruit quality, particularly fruit size and portion of class I and its effects on June drop and return bloom as well as evaluate fruit maturation with the new, non-invasive DA-meter. Moderately flowering apple trees cv.’Gala Mondial’ at Klein Altendorf under white hail net in 2016 were subjected to four crop load motions: a) shading (90% for 77 daylight hours) at the end of May, b) mechanical blossom thinning with the Bonner device with three horizontal rotors at the balloon stage, and c) hand thinning at the end of June, with d) a combination trial of b) and c) adjacent un-thinned apple trees served as control. The weaker (320 rpm) and the stronger (360 rpm) mechanical thinning both at 5.5 km h−1 tractor speed caused a 5% or 22% reduction in fruit set, followed by shading with 27% reduction in comparison with the control trees. After June drop, the stronger mechanical thinning reduced fruit set by 23% and the combined mechanical and hand-thinning by 67%, while shading caused a reduction of 99% at 50°N and without spring frosts. The best pack-out viz. greatest percentage (86.8%) of fruits >70 mm diameter was achieved in the combined mechanical and hand thinning followed by 53.8% in the hand thinning, the strong mechanical thinning with 21.4% and control fruit with only 19.4% resulting in a ca. 68% increase in both class I and II fruit with an additional economic net gain of 3500 €/ha. The relationship between the DA-meter and Streif index is delineated to determine optimum harvest date (OHD). Although apple cv. ‘Gala’ appears insensitive to alternate bearing, return bloom in the control was 4–6, in the stronger mechanical thinning (360 rpm) 5–7, in the hand thinning 6–8 and in the combined mechanical and hand thinning as strong as 8–9 on the 0 (no flowers) − 9 (white blossom) scaleand reflects the physical response of the tree to the previous CLM.© Elsevier B.V.

Determination of the Optimum Harvest Window for Apples Using the Non-Destructive Biospeckle Method.

Determination of the optimum harvest window plays a key role in the agro-food chain as the quality of fruit depends on the right harvesting time and appropriate storage conditions during the postharvest period. Usually, indices based on destructive measurements are used for this purpose, like the De Jager Index (PFW-1), FARS index and the most popular Streif Index. In this study, we proposed a biospeckle method for the evaluation of the optimum harvest window (OHW) of the “Ligol” and “Szampion” apple cultivars. The experiment involved eight different maturity stages, of which four were followed by long cold storage and shelf life to assist the determination of the optimum harvest window. The biospeckle activity was studied in relation to standard quality attributes (firmness, acidity, starch, soluble solids content, Streif Index) and physiological parameters (respiration and ethylene emission) of both apple cultivars. Changes of biospeckle activity (BA) over time showed moderate relationships with biochemical changes during apple maturation and ripening. The harvest date suggested by the Streif Index and postharvest quality indicators matched with characteristic decrease in BA. The ability of biospeckle method to characterize the biological state of apples was confirmed by significant correlations of BA with firmness, starch index, total soluble solids and Streif Index, as well as good match with changes in carbon dioxide and ethylene emission. However, it should be noted that correlations between variables changing over time are not as meaningful as independent observations. Also, it is a well-known property of the Pearson’s correlation that its value is highly susceptible to outlier data. Due to its non-selective nature the BA reflected only the current biological state of the fruit and could be affected by many other factors. The investigations showed that the optimum harvest window for apples was indicated by the characteristic drop of BA during pre-harvest development. Despite this, at the current state of development the BA method cannot be used as an indicator alone. Due to rather poor results for prediction in OHW the BA measurements should be supported by other destructive methods to compensate its low selectivity.

Optimal Illumination-Detection Distance and Detector Size for Predicting Braeburn Apple Maturity from Vis/NIR Laser Reflectance Measurements

The storage potential of apples highly depends on the maturity at harvest. Optical methods have been proposed to measure maturity in a fast, reliable and non-destructive way. However, the signal is often composed of photons with different penetration depths into the material. An attempt to separate these photons might result in more precise correlations with quality attributes, as these could relate to a specific layer/depth into the sample. Therefore, a Vis/NIR spatially resolved laser reflectance setup was used, combining a supercontinuum laser and a monochromator to illuminate samples with a monochrome focused beam in the 550–1000 nm wavelength range. A panchromatic camera was used to obtain diffuse reflectance profiles at each wavelength. In the period starting 50 days before until 11 days after commercial harvest, 320 Braeburn apples were measured. Partial least squares regression models were developed to relate apple maturity/quality to the diffuse reflectance spectra at different distances from the illumination point. The effect of detector size (spatial bandwidth) was also evaluated. A bandwidth of 0.82 mm in combination with a parameter specific illumination-detection distance, gave the best results. Using an internal test set, an R 2 of prediction of 0.98 and 0.93, and a ratio of prediction to performance (RPD) of 5.84 and 3.42, predicting, respectively, the Streif index and starch conversion values was obtained. The predictions of soluble solids content (SSC) (R 2 of 0.81; RPD of 2.04) and firmness (R 2 of 0.65; RPD of 1.66) were less accurate. Also, worse predictions were obtained using an external test set.

Measurement of ethylene production as a method for determining the optimum harvest date of ‘Jonagored’ apples

ABSTRACT The measurement of ethylene concentration in the apple core is considered a good method of determining OHD, but requires high accuracy and expensive equipment. The measurement of ethylene production seems to be a technologically easier method. During research conducted in the years 2003-2008, measurements of ethylene production were evaluated as a method for determining the harvest maturity of ‘Jonagored’ apples intended for storage. Measurements were carried out every 4-5 days starting a few weeks before the estimated harvest date. Apples were picked on four dates and after five months the loss of mass, firmness, TSS and TA was measured, the incidence of physiological disorders and fungal diseases was assessed and sensory tests were conducted to evaluate storability. Based on this evaluation it was determined which of those dates was OHD. After a period of low ethylene production, the production accelerated rapidly to reach an average level between 10.0 and 12.5 ppm kg-1 hr-1 on the OHD. Later, ethylene production rose still more sharply and quickly reached several dozens of ppm kg-1 hr-1. The accuracy of the new method was compared with other methods used to determine the maturity stage. The results obtained through the measurement of ethylene production showed the least deviation from the six-year average and only the results obtained using the Streif index method, which may be unreliable for some cultivars according to the literature, had a comparable margin of error.

The influence of harvest maturity and basic macroelement content in fruit on the incidence of diseases and disorders after storage of the ‘Ligol’ apple cultivar

ABSTRACT Research was carried out during the 1999-2007 growing and storage season using ‘Ligol’ apples from trees grafted on M.26, and fertilised in accordance with recommendations for commercial orchards. The approximate optimum harvest date was determined mainly on the basis of starch index measurements and Streif index calculations, evaluated 7-8 times every 4-5 days each year. In addition to samples collected to determine OHD each year, there were four harvests of fruit intended for storage. The apples were stored in a cold storage room at 1-2°C and RH of around 90% for about five months. Following a storage period lasting the same number of days for each harvest, the quality of fruits was examined and the correlation between the concentration of minerals in apples and all fungal diseases and physiological disorders was calculated. In years with high precipitation in the period preceding the harvest, the share of fruits affected by fungal diseases and physiological disorders after storage depended more on weather conditions prevailing in the growing season than on the harvest date. The incidence of bitter pit increased with the number of days preceding OHD. Other recorded losses were caused by internal breakdown and superficial scald, but they were small and did not seem significant for ‘Ligol’ apples. Each characteristic mineral concentration in the fruit at harvest (N, P, K, Ca and Mg) was correlated with the incidence of physiological disorders and/or fungal diseases. The incidence of bitter pit and lenticel blotch pit and the sum of physiological disorders increased along with the increase in nitrogen concentration. The feature that best predicted the storability of ‘Ligol’ was the K/Ca ratio.

Reflective mulch enhances ripening and health compounds in apple fruit

The objective of the study was to improve fruit quality, including health compounds, by improving light utilization for fruit crops under hail net. Four reflective mulches including plastics such as Extenday® and a bio-degradable paper were spread in the alleyways of a cv. 'Gala Mondial' apple orchard on 10 August 2010 5 weeks before anticipated harvest. Reflective mulch affected neither fruit firmness nor sugar, but accelerated starch breakdown, indicative of riper fruits (smaller Streif index), compared with the uncovered grass alleyway (control). Reflective mulches also improved fruit quality such as red coloration of cv. 'Gala Mondial' apples. This was due to significantly enhanced flavonoids and anthocyanins. Flavonoids increased up to 52.4% in the Extenday® treatment (29.2 nmol cm(-2) in the grass control versus 44.5 nmol cm(-2) fruit peel with reflective mulch). Similarly, reflective mulch improved anthocyanin content in cv. 'Gala Mondial' peel up to 66% compared to grass control (14.5 nmol cm(-2) in control fruit versus 24.1 nmol cm(-2) with reflective mulch). The reflective mulch did not affect chlorophyll and carotenoid content in the 'Gala' fruit peel. Overall, the application of reflective mulches improved fruit quality in terms of better coloration and health compounds and accelerated ripening, leading to higher market value.

Tailoring Organic Apples by Cultivar Selection, Production System, and Post-harvest Treatment to Improve Quality and Storage Life

A series of pre- and post-harvest experiments were conducted to enhance apple tree productivity and improve fruit quality and storage life by altering production system and post-harvest treatments in an organic orchard. Increasing the light distribution and carbohydrate uptake (summer pruning and covering the orchard ground with reflective textile) improved tree productivity, fruit color, content of anthocyanin, ascorbic acid, and total phenolic compounds and reduced incidence of fungal storage diseases. Optimal harvesting time could be determined from the starch index in some cultivars, whereas the Streif index [firmness (soluble solids concentration × starch hydrolysis score)−1] was more accurate for other cultivars. In yet others, titratable acidity and flesh firmness also produced important information. By contrast, soluble solids concentration and skin color are not useful as a result of their sensitivity to weather conditions and light intensity. Post-harvest fruit treatment with hot water (46 °C for 120 seconds) decreased fungal decay during storage in two cultivars, whereas spraying the fruit with 10% ethanol decreased fungal decay in all investigated cultivars. Optimization of storage conditions [cultivar-specific controlled atmosphere (CA) and ultra-low oxygen (ULO) storage procedures] maintained fruit quality and reduced the amount of fungal decay.

QUALITY AND ‘CONFERENCE’ PEAR STORABILITY AS INFLUENCED BY PREHARVEST SPRAYS OF CALCIUM CHLORIDE

The aim of the study was to examine impacts of calcium chloride (CaCl2) sprays on quality and ‘Conference’ pear (Pyrus communis L.) storability. The experiment was carried out during 2002–2008 at a commercial orchard in Central Poland, on mature pear trees grafted on Quince S1 (Cydonia oblonga Mill.). The trees were planted at a spacing of 3.5 × 1.5 m, on a coarse-textured soil with low organic matter status, optimal pH, and adequate contents of available macro- and micronutrients. The efficiencies of two, four, or six sprays of CaCl2 were examined. The first treatment in all CaCl2 spray combinations was made six weeks after full bloom (the end of June), and the last one two weeks before harvest. Intervals between measures in the combinations of four and six sprays of CaCl2 were 4 and 2 weeks, respectively. A rate of CaCl2 depended on the tree growth stage; up to mid July a dose of CaCl2 was 2 kg ha−1, whereas in the later period 4 kg ha−1. Calcium chloride sprays were made at a volume of 1000 dm3 of water per ha. The trees unsprayed with CaCl2 served as the control. Because in 2005 and 2007 most flowers were damaged by spring frost, CaCl2 sprays in those years were not performed. The obtained results demonstrated that CaCl2 sprays did not affect fruit yield, mean fruit weight, fruit russeting, and ground skin color, soluble solids concentration (SSC), and titratable acidity of fruit at harvest. At harvest, in 2 out of 5 years of the study, pears sprayed six times with CaCl2 had increased firmness, and decreased values of both starch index and Streif's index. Only six sprays of CaCl2 enhanced pear Ca level. After storage (150 days at 0°C plus two days at room temperature) pears sprayed six times with CaCl2 were firmer, greener, and less sensitive to internal browning than those of the control plots. In three out of five years, pears sprayed six times with CaCl2 contained more organic acids after storage than the control fruit. Preharvest CaCl2 sprays had no effect on SSC in pears and their decay after storage. It is concluded that in ‘Conference’ pear orchards six preharvest sprays of CaCl2 should be applied to improve fruit storability.

Evaluating the Streif index against commercial subjective predictions to determine the harvest date of apples in South Africa

For the local deciduous fruit industry, which mainly exports fruit, determination of the optimum physiological harvest maturity for apples to ensure high fruit quality after long-term storage is still an important goal. This is performed by a subjective determination based on a weekly rate of change of all or some of the ripening parameters such as fruit firmness. In Europe, the Streif index (SI) has been implemented to reduce this subjectivity. The aim of this project was to evaluate this index under local conditions. Historical physiological data for Golden Delicious and Starking apples (Malus domestica Borkh.) from various orchards in the Ceres area were analysed. Significant correlations were obtained between the SI and subjective predictions of the release date for harvesting, after adapting the local starch breakdown values. However, during seasons when the starch conversion rates were very low during the early season, the SI alone may not be sufficient to indicate the release date for harvesting. A multilinear regression equation was also fitted to the maturity data. Likewise the accuracy of this model was influenced by season and variation between individual sites. Both methods can be applied commercially to support the otherwise subjective determination of the harvest dates.

Responsiveness of ‘Conference’ pears to 1‐methylcyclopropene: the role of harvest date, orchard location and year

In some pear varieties like 'Conference', 1-methylcyclopropene (1-MCP) treatment often impairs the ripening process indefinitely and the pears remain 'evergreen'. To better understand this behaviour, the influence of the harvest date, orchard location and year on the effectiveness of 1-MCP treatment was investigated. Pear softening was inhibited by 1-MCP treatment and the effectiveness of the treatment depended on harvest date, orchard location and year. Differences in the rate of softening in 1-MCP-treated pears depended mainly on the fruit physiological maturity at the moment of 1-MCP treatment. Accordingly, the combination of the Streif index and ethylene production at harvest appeared to be able to predict the evergreen behaviour. Treated pears with a low Streif index (<0.8) and high ethylene production at harvest (≥0.23 µL kg(-1) h(-1)) maintain significantly high firmness but did soften during shelf life, reaching acceptable eating quality. Evergreen behaviour was mainly influenced by the initial fruit maturity and especially by the ability of the fruit to produce ethylene at the moment of treatment. More mature fruit were able to overcome the inhibition by 1-MCP, and the solution to prevent evergreen behaviour therefore lies in the adequate determination of harvest maturity.