Fruit Soluble Solids Content Research Articles

Integrated spectral and image analysis of hyperspectral scattering data for prediction of apple fruit firmness and soluble solids content

Spectral scattering is useful for assessing the firmness and soluble solids content (SSC) of apples. In previous research, mean reflectance extracted from the hyperspectral scattering profiles was used for this purpose since the method is simple and fast, and also gives relatively good predictions. The objective of this study was to improve firmness and SSC prediction for ‘Golden Delicious’ (GD), ‘Jonagold’ (JG), and ‘Delicious’ (RD) apples by integration of critical spectral and image features extracted from the hyperspectral scattering images over the wavelength region of 500–1000 nm, using spectral scattering profile and image analysis techniques. Scattering profile analysis was based on mean reflectance method and discrete and continuous wavelet transform decomposition, while image analysis included textural features based on first order statistics, Fourier analysis, co-occurrence matrix and variogram analysis, as well as multi-resolution image features obtained from discrete and continuous wavelet analysis. A total of 294 parameters were extracted by these methods from each apple, which were then selected and combined for predicting fruit firmness and SSC using partial least squares (PLS) method. Prediction models integrating spectral scattering and image characteristics significantly improved firmness and SSC prediction results compared with the mean reflectance method when used alone. The standard errors of prediction (SEP) for GD, JG, and RD apples were reduced by 6.6, 16.1, 13.7% for firmness ( R pred-values of 0.87, 0.95, and 0.84 and the SEPs of 5.9, 7.1, and 8.7 N), and by 11.2, 2.8, and 3.0% for SSC ( R pred-values of 0.88, 0.78, and 0.66 and the SEPs of 0.7, 0.7, and 0.9%), respectively. Hence, integration of spectral and image analysis methods provides an effective means for improving hyperspectral scattering prediction of fruit internal quality.

Harvesting fruit of equivalent chronological age and fruit position shows individual effects of UV radiation on aspects of the strawberry ripening process

The effect of UV radiation on fruit secondary compounds of strawberry cv ‘Elsanta’ was recorded taking chronological age and fruit position on the truss into account. When fruit of similar age post-anthesis, and truss position were compared, we found that the concentration of secondary compounds differed according to fruit position on the truss. UV radiation hastened the rate of colour development and resulted in an increase in fruit anthocyanin (14–31%), flavonoid (9–21%) and phenolic (9–20%) contents at harvesting; but it had no effect on fruit soluble solid content, pH and volatile composition. It did, however, increase leaf flavonoid (16%) and phenolic (8%) concentrations. Fruit ripened under a UV transparent film were firmer, smaller but greater in number than fruit ripened under a UV opaque film. Overall, the results indicate that UV radiation does not affect all aspects of strawberry ripening but independently alters rate of colour development and fruit firmness.

Study of Fluorescence Spectrum for Measurement of Soluble Solids Content in Navel Orange

On-line nondestructive estimation of fruit internal quality greatly benefits the consumer and the fruit industry as a whole because it can ensure the safety and processed product consistency. This research was aimed to build prediction model of soluble solids content (SSC) in navel oranges using ultraviolet lamp induced fluorescence technique. Total 254 navel oranges were separated into the calibration set (170 samples) and prediction set (84 samples). The actual SSC of navel oranges were measured using a digital refratometer. A characteristic wavelength range (385-414nm) was found to build a partial least squares (PLS) model for predicting the SSC in navel oranges. The correlation coefficient (r) between the predicted and actual SSC was 0.9161 and 0.8295 for calibration and prediction set, respectively. The root mean square error of calibration (RMSEC) and prediction (RMSEP) set was 1.0797 and 1.4283, respectively. The results showed that fluorescence spectrum can nondestructively determine SSC in fruit.

Phenolic Composition and Antioxidant Capacity of Newly Developed Strawberry Lines from British Columbia and Quebec

The total phenolic composition (TPC) and the total antioxidant capacity (TAC) of eleven strawberry genotypes selected from the AAFC breeding program (BC2-72-17, BC2-90-43, BC96-33-4 and BC98-49-34 from British Columbia; and APF937-1, APF939-71, LL981-24, LL9819-14, LL982-14, LL0220-10 and SJ9332-7 from Quebec) were evaluated using high-performance liquid chromatography (HPLC) and ferric reducing/antioxidant power (FRAP) assays. TPC and TAC values of these genotypes were compared to those of four commercially grown cultivars (‘Chambly,’ ‘Kent,’ ‘Veestar’ and ‘Yamaska’) and the effects on fruit quality and shelf life were studied. Several groups of phenolic compounds, including anthocyanins, flavonols, hydroxycinnamic, ellagic and benzoic acids, were identified and quantified by HPLC. Significant variation of TPC was observed between genotypes, and anthocyanins were found to be the predominant phenolic group, contributing to 79.2% of the TPC. A significant correlation (r = 0.96) was observed between TPC and anthocyanin content. BC2-72-17 had the highest anthocyanin content and differed significantly from the other genotypes. Although the highest TPC (2123.8 μg g−1) was found in BC2-72-17, this genotype did not have the highest antioxidant capacity. The highest TAC (2259.0 μg g−1) was found in BC2-90-43, indicating that other phenolics may have made a greater contribution than anthocyanins to the high TAC. At room temperature, LL0220-10, SJ9332-7 and ‘Yamaska’ had a three-day shelf life, while it was only two days for all other genotypes. There was a negative correlation between shelf life and ellagic acids, flavonol and anthocyanin levels but this relationship was not significant (p > 0.0.). The fruit soluble solids content (SSC) and titratable acidity (TA) varied between genotypes. ‘Veestar’ and LL981-24 had the highest SSC (7.5). These results point to the importance of identifying genotypes with high phenolic monomer activities in screening for lines with high TAC, to ensure their use in breeding programs aimed at improving the nutritional value of strawberry.

Relationship between Fruit Soluble Solid Content and the Sucrose Concentration of the Phloem Sap at Different Leaf to Fruit Ratios in Tomato

Tomato fruits accumulate most of their solid contents during rapid fruit development. The balance of water transport to assimilate transport into fruits during that stage is an important factor that determines the final solid content of fruits at harvest. In this study, the relationship of sucrose concentration of the phloem sap to the solid content of rapidly growing fruits was investigated. At the anthesis of the second truss, the stem just above the first truss was heat-girdled, while newly emerging leaves above the second truss were pinched regularly to diminish cross translocation of carbohydrates between the source-sink unit, consisting of the second truss and three leaves below, and other parts of the plant. The leaf to fruit ratio (LFR) as the number of leaves per fruit of this isolated source-sink unit was manipulated at the fruit set of the truss. When LFR was increased from 0.2 to 1, fruit dry weight increased linearly from 3.5 to 7 g, but it saturated beyond the LFR of 1. By contrast, the contents of dry matter and soluble sugars on a fresh weight basis increased linearly within the whole range of LFR from 0.2 to 3. The sucrose concentration of the phloem sap, collected from the pedicel by the modified EDTA method, also increased as LFR increased, and a positive correlation was observed between sucrose concentration of the phloem sap and the contents of dry matter and total soluble sugars. These data suggested that solid content can be increased in a wide range of LFR in proportion to the sucrose concentration of the phloem sap.

SPATIAL AND TEMPORAL VARIABILITY OF YIELD AND FRUIT QUALITY IN APPLES

The objective of this work was to study the spatial and temporal variability of yield and fruit quality in an apple (Malus × domestica) orchard for three consecutive years. The orchard was located in Ptolemaida area, northern Greece and two cultivars were studied, 'Red Chief' and 'Fuji'. For yield mapping, fruit production per five trees was weighed and geographical position in the middle of the five trees was recorded using a palm-top computer with GPS. Fruit samples were randomly selected from each yield measuring point and fruit quality was measured immediately and after 4 months cold storage at 0°C. Fruit quality included fruit mass, skin colour, flesh firmness, juice soluble solids content, pH and acidity. Yield and quality characteristics maps were generated using Surfer software. Significant spatial variability in yield and quality were found. Spatial variability for quality was lower than the one for yield. Fruit soluble solids content and flesh firmness showed low and fruit mass, acidity and skin colour showed high spatial variability. Temporal variability (differences from year to year) in yield was low in 'Red Chief' and high in 'Fuji' trees due to alternate bearing. Temporal variability was significant for quality characteristics, probably due to differences in weather conditions from year to year. During cold storage, flesh firmness and acidity decreased and soluble solids content increased in 'Red Chief or did not change in 'Fuji' fruit.

EFFECTS OF COLLETOTRICHUM GLOEOSPORIOIDES AND MONILINIA FRUCTICOLA ON QUALITY OF RED FLESH DRAGON FRUIT (HYLOCEREUS POLYRHIZUS)

ISHS International Symposium Postharvest Pacifica 2009 - Pathways to Quality: V International Symposium on Managing Quality in Chains + Australasian Postharvest Horticultural Conference EFFECTS OF COLLETOTRICHUM GLOEOSPORIOIDES AND MONILINIA FRUCTICOLA ON QUALITY OF RED FLESH DRAGON FRUIT (HYLOCEREUS POLYRHIZUS)

CHLOROPHYLL FLUORESCENCE AND FRUIT QUALITY DURING STORAGE OF MANGO FRUIT IN MODIFIED ATMOSPHERE PACKAGING

Chlorophyll fluorescence was investigated as a possible nondestructive tool to detect quality changes in mangoes stored in modified atmosphere packaging. Mangoes were packed in MTEC breathable film and stored at 15 or 25°C. The chlorophyll fluorescence parameters of minimal fluorescence (Fo), maximal fluorescence (Fm) and potential quantum yield (Fv/Fm) as well as fruit firmness, skin colour and soluble solids content were evaluated every 3 d during storage. CO 2 and O 2 concentrations in the package headspace were determined daily. Chlorophyll fluorescence parameters (Fv/Fm, Fv and Fm) declined over storage time whereas the firmness changed immediately at 25°C and after 3 d at 15°C. The fluorescence parameters did not change until about 12 d of storage, thus fluorescence did not follow the changes in firmness. However, fruit firmness also declined during the storage period. Chlorophyll fluorescence parameters (Fv/Fm, Fv and Fm) and fruit firmness of mangoes stored at 15°C were higher than those of mangoes stored at 25°C and these differences increased with storage time until 15 d of storage after that firmness of the fruit from 15°C was the same as that from 25°C. These results suggest that chlorophyll fluorescence may be useful to determine changes in mango fruit quality nondestructively.

Growth, yield and water use efficiency response of greenhouse-grown hot pepper under Time-Space deficit irrigation

Greenhouse-grown hot pepper was used to investigate the effect of Time-Space deficit irrigation (TSDI), a newly developing irrigation technique based on regulated deficit irrigation (RDI) and partial rootzone drying (PRD), by measuring plant growth, yield and irrigation water use efficiency. The treatments consisted of factorial combinations of three factors, organized following an orthogonal L 9 (3) 4 test design with four growing stages. Three irrigation strategies (conventional furrow irrigation with full-water when soil water content was lower by 80% of field capacity (F), conventional furrow irrigation with 50% of full-water (D) and alternate furrow irrigation with 50% of full-water (P)) as the main plot factor were applied to select the optimum irrigation parameter at different stages of crop development, the treatment in which irrigation water was applied to both sides of root system when soil water content was lower by 80% of field capacity during all stages was considered as control (FFFF). Water consumption showed some significant effect of irrigation treatment during the growing period of different drought stress patterns application, and therefore decreased in these treatments to a level around 54.68–70.33% of FFFF. Total dry mass was reduced by 1.17–38.66% in TSDI treatments compared to FFFF. However, the root–shoot ratio of FFFF was lower than other treatments and the differences from FFFF and other TSDI treatments were statistically significant. The highest total fresh fruit yield (19.57 T ha −1) was obtained in the FFFF treatment. All deficit irrigations increased the water use efficiency of hot pepper from a minimum of 1.33% to a maximum of 54.49%. At harvest, although there was difference recorded as single fruit weight and single fruit volume were reduced under the TSDI treatments, total soluble solids concentration of fruit harvested under the water-deficit treatments were higher compared to FFFF.

RELATIONSHIP BETWEEN SOIL AND LEAF POTASSIUM CONTENT AND 'VALENCIA' ORANGE FRUIT QUALITY

In order to evaluate the relationship between orange fruit quality and potassium concentration in soil and leaves, thirty 20-year-old 'Valencia' orange on 'Cleopatra' mandarin were evaluated in 2006, in Nirgua, Yaracuy State, Venezuela. For each plant 12 samples of 12 fruits each were analysed. The following variables were determined: polar and equatorial diameter of fruit, fresh mass, skin thickness and percentage, juice percentage, total titratable acidity (TA), soluble solids concentration (SSC), and SSC/TA ratio. Fifteen samples of soil and leaves were taken for potassium analysis. A correlation was obtained between soil potassium content and some fruit quality attributes (skin and juice percentages). Leaf potassium had a positive correlation with fruit SSC. It was found that the greater potassium level, minor fresh mass and juice content in the fruits along with higher skin proportion and SSC.

Relationship between early watercore development and leaf photosynthesis or partitioning of photosynthates in apple

Seasonal changes in leaf photosynthetic rate and partitioning of 13C taken up by leaves were compared in relation to the development of early watercore using susceptible ‘Orin’ and resistant ‘Fuji’ apples ( Malus domestica Borkh.). There was no difference between the cultivars in leaf photosynthetic rate from mid-July to mid-October. The extent of watercore in ‘Orin’ increased from mid-July and peaked in late-August, followed by a decrease through mid-October, while no watercore was detected during the experimental period in ‘Fuji’. Fruit fresh weight and soluble solids content (SSC) were higher in ‘Orin’ than ‘Fuji’ during the earlier stages. Leaf dry weight of ‘Orin’ was higher than that of ‘Fuji’ throughout the experimental period. Accumulation of dry matter in the fruit increased in both cultivars and ‘Orin’ kept significantly higher level than ‘Fuji’ from mid-July to mid-October. The amount of 13C distributed to ‘Orin’ fruit at 5 days after labeling was significantly higher than ‘Fuji’ in mid-July just before watercore started to occur. 13C taken up by ‘Orin’ fruit with prevalent watercore was also higher than ‘Fuji’ in late-August but the difference was not significant. In mid-October when early watercore was gradually reducing, 13C recovered by ‘Orin’ fruit decreased and was significantly lower than ‘Fuji’. The difference of partitioning pattern of 13C between the cultivars was associated with the susceptibility to early watercore as well as the changes in fruit growth and SSC. The seasonal changes in the amount of 13C distributed to ‘Orin’ fruit were also related to the fluctuations in watercore severity. The results suggest that active phloem transport might be the cause of early watercore in our previous work, which might be induced by the increased partitioning of assimilates to the fruit during summer in susceptible ‘Orin’ compared to resistant ‘Fuji’ and not by the higher potential of leaf photosynthesis.

The effectiveness of grafting to improve tomato fruit quality

The possibility of applying grafting to improve fruit quality has been scarcely investigated. Different shoot tomato ( Solanum lycopersicum) genotypes were grafted onto distinctly-different tomato rootstocks and the effect of the rootstock on two important fruit quality parameters, soluble solids content (SSC) and titratable acidity (TA), was studied under both non-saline and saline conditions. Increased SSC and TA in fruits from grafted plants grown under saline conditions were observed on different grafting combinations. One of these rootstocks (cv. Radja) was able to induce increases in both fruit yield and fruit quality traits of the scion. When recombinant inbred lines (RILs) from the crossing of the cultivated tomato and wild tomato ( Solanum cheesmaniae) were tested as rootstocks, using the commercial hybrid ‘Boludo’ as scion, the rootstock also improved SSC and TA when grafted plants were grown under non-saline conditions. On the whole, these results show the effectiveness of grafting with respect to upgrading of fruit quality in tomato, which is of great importance as grafting is a rapid and efficient alternative to achieve this goal.

Daily based quantitative nutrient management in rockwool hydroponics: Growth and yield of tomato and nutrient use at elevated CO2

The efficacy of daily quantitative nutrient management (QNM) in tomato rockwool hydroponics under CO2-enriched conditions was tested. Three levels of nutrient supply based on daily water uptake were compared with conventional electrical conductivity (EC)-based management. A newly developed automatic QNM system with server and client controller prototypes was used to control nutrient supply. Plants in a greenhouse were supplied with 0.5 (S), 1.0 (M) or 1.5 (L) times the optimal daily amount of nutrients for normal CO2 conditions from October 2009 to February 2010. EC-based management produced highest cumulative total fruit yield during 16 weeks of fruit harvest followed by L, M and S treatments, in that order. There was no significant difference in cumulative marketable fruit yields in EC-based management, L and M treatments, but marketable yields from these three treatments were significantly higher than S treatment. Fruit dry matter content and fruit soluble solid content in QNM treatments were almost the same or higher than fruit grown in EC-based management. The amount of nutrient used during the experiment in S, M and L treatments was 10, 24 and 42%, respectively, of the amount used for EC-based management. Nutrient use efficiency (NUE), defined as marketable fruit yield per unit of the amount of nutrient used, in all three QNM treatments was higher than in EC-based management. Thus, daily QNM can reduce nutrient use without lowering fruit yields and quality under CO2-enriched conditions. The M or L treatment provided optimal balance between fruit yield and NUE. The L treatment gave slightly higher marketable yield but lower NUE than M treatment.

The Measurement of Soluble Solids Content in Snake Fruit (Salacca Edulis Reinw) cv. Pondoh Using A Portable Spectrometer

In this research we reported the use of near infrared spectroscopy for nondestructive soluble solids content (SSC) measurement in intact snake fruit (Salacca edulis Reinw) cv. Pondoh. The spectra of 100 samples were acquired in the range of 300-1040 nm using an available, low cost portable spectrometer (VISNIR USB4000). The spectrometer used an array of linear CCD as a detector. The LS-1 Tungsten Halogen lamp is used as light source. This system is also equipped with a fiber optic. Snake fruits were placed on the sample holder and the spectra were measured using 100 ms of integration time and 50 scans for averaging. The spectra were acquired in two different positions in the middle of fruit. The total scanning time was 10 s for each fruit. The SSC of snake fruits were measured destructively following the spectra measurement using a digital refractometer. A portion of snake fruit flesh with associated with the point of spectra measurement was cut and juiced. Then the juice of snake fruit was placed on a digital refractometer. The SSC was quantified in Brix value. The trial free version of The Unscrambler V.9.1 was used as chemometrics tools to extract the useful information from the spectra. The calibration model was developed using Partial Least Squares Regression 1 (PLSR1) for three types of spectra, original, smoothing and second derivative spectra. The calibration model was evaluated using some parameters such as coefficient of determination (R2), standard error of prediction (SEP), bias between actual and predicted SSC value and ratio prediction to deviation (RPD) parameter. The possibility of using near infrared spectroscopy to measure SSC of intact snake fruit nondestructively was successfully demonstrated. The best calibration model with 3.32 of RPD value could be obtained.

A Copper-based Fungicide Has Minimal Effects on Tart Cherry Fruit Quantity and Quality

Copper-based fungicides are effective for managing cherry leaf spot disease incited by Blumeriella jaapii (Rehm) Arx. However, their application has been associated with bronzing discoloration of tart cherry (Prunus cerasus L.) foliage. This work explored the consequences of foliar applications of a copper-based fungicide for tart cherry fruit quantity and quality. ‘Montmorency’ tart cherry trees were subjected to one of the following fungicide programs in 2007, 2008, and 2009: synthetic fungicides only, synthetic fungicides integrated with a copper-based fungicide, or not sprayed. Each year, the number of fruits per shoot and fruit fresh weight and soluble solids concentration (SSC) were measured three to six times during drupe development. Repeated measures indicated no collection date × fungicide program effect on the mean number of fruits (P ≥ 0.48) and SSC (P ≥ 0.14) in all years or on fresh weight in 2008 and 2009 (P ≥ 0.58). There was a collection date × fungicide program effect (P = 0.02) on mean fresh weight in 2007. On 6 July 2007, trees assigned to the integrated copper program were observed having 23% and 27% lower fruit fresh weights than trees assigned to the nonsprayed and synthetic programs, respectively. However, pairwise comparisons indicated no difference in fresh weight between the integrated copper and the nonsprayed programs (P = 0.26) and no difference between the integrated copper and synthetic programs (P = 0.25) on the final collection date of 2007. In 2007, fresh weight decreased slightly (slope = –0.08, P = 0.05) as leaf bronzing severity increased, whereas SSC increased slightly (slope = 0.31, P = 0.06). In 2008 and 2009, there was no relationship between bronzing severity and fresh weight or SSC (P ≥ 0.34). These results indicate that applied copper does not lead to fewer fruits per shoot or reductions in fresh weight or SSC of mature fruit and that the observed range of leaf bronzing severity had little to no influence on fresh weight and SSC.

Effect of ethylene and 1-MCP on post-harvest physiology and on expression of the ethylene receptor genes PpETR3 and PpERS2 in pear (Pyrus pyrifolia Nakai ‘Kikusui’) fruit

SummaryExogenous ethylene and 1-MCP were investigated for their potential effects on fruit quality, post-harvest physiology, and expression of the ethylene receptor genes PpETR3 and PpERS2 in ‘Kikusui’ pear fruit. The results showed that exogenous ethylene treatment promoted a reduction in fruit firmness and soluble solids content (SSC), an increase in the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) at a later stage of fruit storage, improved the rates of respiration and ethylene release, and up-regulated expression of the PpERS2 gene from 0 – 9 d after harvest, but did not affect expression of PpETR3. However, the effects of 1-MCP on fruit quality and post-harvest physiology were contrary to those of ethylene. 1-MCP up-regulated expression of the PpETR3 gene from0 – 9 d and down-regulated expression of PpERS2 from 6 – 15 d after harvest. These data indicate that exogenous ethylene or 1-MCP could accelerate or inhibit pear fruit ripening during storage, respectively. At different stages of storage, ethylene and 1-MCP had different effects on the expression of PpETR3 and PpERS2. Moreover, the expression patterns of PpETR3 and PpERS2 during fruit ripening suggest that these two ethylene receptors have important functions during ethylene signal transduction.

Optimal Wavelength Selection for Hyperspectral Scattering Prediction of Apple Firmness and Soluble Solids Content

Hyperspectral scattering is a promising technique for nondestructive quality measurement of apple fruit, and extraction of the most useful information from the hyperspectral scattering data is critical for accurate assessment of fruit firmness and soluble solids content (SSC). In this article, a hierarchical evolutionary algorithm (HEA) approach coupled with subspace decomposition and partial least squares regression is proposed to select the optimal wavelengths from hyperspectral scattering profiles of 'Golden Delicious' apples for predicting fruit firmness and SSC. Six hundred apples were tested in the experiment, 400 of which were used for calibration and the remaining 200 apples for validation. Seventeen optimal wavelengths were selected for firmness prediction, which nearly spanned the entire spectral range of 500 to 1000 nm, and 16 optimal wavelengths, all of which were above 600 nm, were selected in the SSC prediction model. The model using the 17 optimal wavelengths for predicting firmness yielded better results (r = 0.857, root mean square error of prediction or RMSEP = 6.2 N) than the full spectrum model (r = 0.848, RMSEP = 6.4 N). For predicting SSC, the model using the 16 optimal wavelengths also yielded better results (r = 0.822, RMSEP = 0.78%) than the full spectrum model (r = 0.802, RMSEP = 0.83%). The HEA approach provided an effective means for optimal wavelength selection and improved the prediction of firmness and SSC in apples compared with the approach using the full spectrum.

EFFECT OF AUTUMN CALCIUM SPRAY AT A HIGH RATE ON ‘GRANNY SMITH’ APPLE QUALITY AND STORABILITY

The aim of the study was to examine effect of autumn calcium (Ca) spray at a high rate on apple quality and storability. The investigation was carried out during 2005–2006 in Isparta district, Turkey, under semi-arid conditions, on mature ‘Granny Smith’ apple trees/M.9 EMLA, planted at a spacing of 3.5 × 1.5 m on fine-textured soil rich in Ca. The trees were sprayed with Ca in summer and/or in autumn, using organically complexed Ca to avoid possible leaf and fruit injuries. In autumn (10 days before harvest), the trees were sprayed with Ca at a rate of 8 kg ha−1. In summer, the another trees were sprayed with Ca six times at a rate of 1.5 kg ha−1 in each measure; the first spray treatment was performed 6 weeks after full bloom, and the others at 7–9 day intervals. The third part of the trees was sprayed with Ca in summer as well as in autumn, at the same terms and rates as given above. Trees unsprayed with Ca served as the control. It was found that Ca sprays in autumn or in summer plus in autumn damaged leaves; however those treatments did not caused defoliation. Calcium sprays had no effect on apple yield, mean fruit weight, fruit skin russeting, and firmness, soluble solids concentration and titratable acidity of fruit at harvest. Fruit flesh Ca concentrations of the control trees were high. However, the highest fruit Ca concentration was recorded on the trees sprayed with Ca in summer plus in autumn. Calcium sprays in summer or in autumn increased fruit Ca concentrations but their effects were weaker than summer plus autumn Ca applications. After 100 days of refrigerated air storage, soluble solids concentration of fruit did not differ between the studied combinations. Only apples sprayed with Ca in summer plus in autumn were firmer and contained more organic acids than the control fruit. During storage, there were neither pathogenic diseases nor physiological disorders. Based on the obtained results we conclude that Ca sprays in summer plus in autumn at high rate can prolong ‘Granny Smith’ apple storage even thought initial fruit Ca concentration is as high as 502–504 mg Ca kg−1 DW or 84.1–84.8 mg Ca kg−1 FW.

Nondestructive measurement of soluble solid content of navel orange fruit by visible–NIR spectrometric technique with PLSR and PCA-BPNN

A relationship was established between the soluble solid content (SSC) of navel orange fruit determined by destructive measurement and visible–near infrared diffuse reflectance spectra in the wavelength range of 350–1800 nm. Multiplicative scatter correction (MSC) and standard normal variate correction (SNV) were applied to the spectra, partial least squares regression (PLSR) and back propagation neural network (BPNN) based on principal component analysis (PCA) were used to develop the models for predicting the SSC of intact navel orange fruit. Thirty-eight unknown samples were used to evaluate the performance of these models. The principal component analysis-back propagation (PCA-BPNN) method with MSC spectral pretreatment obtain the best predictive results, resulting in correlation coefficient, root mean square error of prediction (RMSEP), average difference between predicted and measured values (Bias) of 0.90, 0.68 °Brix and 0.16 °Brix, respectively. Experimental results indicate that PCA-BPNN is a suitable tool to model the non-linear complex system, with additional advantages over PLSR, and the vis/NIR spectrometric technique can be used for measuring the SSC of intact navel orange fruit, nondestructively.

Effect of a postbloom naphthaleneacetic acid thinning spray and hand thinning on quality and quantity of pear fruit (Pyrus communis L.) cv. Harrow Sweet

The effect of naphthaleneacetic acid (NAA) and hand thinning on quality and quantity of pear fruit (Pyrus communis L.) cv. Harrow Sweet was investigated in 2005, 2006 and 2007. The experiment included the following treatments: an unsprayed control, hand thinning to 3 fruit cm-2 of trunk cross-sectional area (TCSA), hand thinning to 6 fruit cm-2 of TCSA, NAA at 8 mg L-1 (2005-2007), NAA at 16 mg L-1 (2006-2007) and NAA at 20 mg L-1 (2007). The same treatments were applied to the same trees in each of the three years. NAA thinning did not reduce yield per tree and had no negative effect on fruit set, yield efficiency, or crop load in any of the years. In 2005 and 2006, NAA and hand thinning significantly increased fruit diameter and weight. In 2007, only NAA at 20 mg L-1 significantly increased fruit diameter and weight relative to the control. Fruit firmness was not influenced by NAA or hand thinning in 2005 or 2007, but in 2006, hand-thinned fruits were significantly less firm than control fruit. Hand thinning to 6 fruit cm-2 of TCSA increased fruit soluble solids content in 2006 and 2007. Neither NAA nor hand thinning influenced total sugars or organic acids in fruit. Key words: Yield, sugars, organic acids, HPLC