Relationship between tissue firmness and optical properties of ‘Royal Gala’ apples from 400 to 1050 nm

Absorption and reduced scattering coefficients were measured between 400 and 1050 nm for ‘Royal Gala’ apples using the inverse adding-doubling technique. Relationships between penetrometer, acoustic firmness and the optical properties are identified. Carotenoid (400–500 nm), and to a lesser extent chlorophyll-a (680 nm), absorptions were found to correlate with penetrometer firmness, with correlation coefficients equal to −0.69 and 0.52 respectively. The reduced scattering coefficient across all wavelengths increased as fruit softened. An average correlation coefficient of −0.68 was found between the reduced scattering coefficient (550–900 nm) and penetrometer firmness. No correlation was found between the AWETA acoustic firmness and either of the optical properties. A correction was developed to improve the correlation between penetrometer firmness and carotenoid absorption. This compensated for errors introduced by light loss in the inverse adding-doubling system and improved the correlation from −0.68 to −0.78.     

Importance of fruit variability in the assessment of apple quality by sensory evaluation

The assessment of produce quality is a major aspect of applied postharvest biology. Horticultural researchers working on organoleptic quality of fruit need objective methods for the evaluation of sensory properties. The development of sensory methodologies specifically for apples highlighted the problem of handling variation due to fruit variability and assessor differences. The aim of this study was to investigate the weight of within-batch variability in sensory evaluation of apples and to propose a methodology that accounts for this variability. Prior to sensory analysis, for three apple cultivars, apples were sorted into homogenous acoustic firmness categories within each cultivar. The discrimination ability of the trained panel was observed not only between cultivars but also within each cultivar for crunchiness, firmness, juiciness and acidity. Following these results, a mixed hierarchical model for the analysis of the sensory data was proposed to measure the contribution of fruit variability to the variability of sensory scores. The results showed the efficiency of the model in quantifying within-batch variability. Fruit sampling and presentation methods as well as data handling procedures are suggested for obtaining reliable sensory results in the assessment of apple quality.     

冰温气调对红富士苹果贮藏效果的影响

研究了冰温条件下不同气体成分对红富士苹果果实生理及贮藏品质的影响。结果表明,八成熟红富士苹果的冰点为-1．5℃,其冰点温度与果实的成熟度呈负相关;适宜的冰温气调贮藏条件可明显地抑制红富士苹果呼吸及乙烯释放速率．减缓果实组织相对电导率的上升和杲肉硬度及可溶性固形物（TSS）的下降速率,贮藏8个月仍能保持良好的品质;红富士苹果较长期冰温贮藏的适宜气体指标为：O2 1％～3％,CO2〈2％。     

苹果双相变动气调贮藏研究

双相变动气调是一项崭新的苹果气调贮藏技术与理论.本文介绍了双相变动气调与传统气调的主要区别,以及在严格对比条件下的试验结果.双相变动气调贮藏红星苹果150天,果实品质与果肉硬度好于冷库,与气调库基本相同,并能明显抑制原果胶水解,乙烯生物合成和MACC累积.     

Utilizing the IAD index to determine internal quality attributes of apples at harvest and after storage

A hand-held instrument (DA Meter, Sinteleia, Bolonga, Italy) which measures chlorophyll nondestructively and gives an I_AD index (index of the absorption difference between 670 and 720 nm), was used to measure quality attributes of three cultivars of apples. A preharvest study conducted in a ‘Starking’ apple orchard found determination coefficients of r² values of 0.79 to 0.64 between the I_AD index and starch levels, firmness, TSS and TA of fruit. Three orchards of ‘Starking’, ‘Granny Smith’ and ‘Pink Lady’ apples were sampled during commercial harvest and the apples held in air storage for up to six months. The I_AD index measured either at harvest or at removal from storage was correlated with TSS, TA and firmness of the apples. The r² values were best for TSS (0.76) and poorest for firmness (0.51). Moreover, the measurement at harvest and at removal from storage gave similar prediction coefficients for quality attributes. This measurement can be used to sort at harvest for different quality classes after storage, or at removal from storage for different marketing classes.     

Instrumental measurement of apple texture: A comparison of the single-edge notched bend test and the penetrometer

The single-edge notched bend (SENB) test is a technique for measuring fundamental properties of materials. This technique is an easily applied measure of fruit texture that is related to sensory characteristics such as ‘crunchiness’ [Vincent, J.F.V., Saunders, D.E.J., Beyts, P., 2002. The use of critical stress intensity factor to quantify “hardness” and “crunchiness” objectively. J. Texture Stud. 33, 149–159]. The present study focuses on the relationship between SENB and the penetrometer test routinely used for fruit quality assessment. Fruit from cultivars Cox's Orange Pippin, Sciros, Sciearly and Scifresh were removed from cold storage at regular intervals, and texture was assessed after 1 and 7 days at 20 °C. Texture was measured using a conventional puncture test with an Effegi probe and a SENB test. During the SENB test, a notched beam of apple tissue was subjected to three-point bending until it broke. Fracture toughness (K_c) and fracture energy (G_c) were calculated, and Low-Temperature Scanning Electron Microscopy (LTSEM) was used to examine the fracture surface following beam failure. Both K_c and G_c were correlated with puncture force, but the relationship was different for Sciros and Sciearly (two siblings from a Gala × Splendour cross) compared to the other cultivars. Sciros and Sciearly apples had higher K_c and G_c values than would be anticipated from measurements of puncture force. This supports the suggestion that these apples are crisper when eaten than might be expected from puncture (penetrometer) values. Comparison of the texture of shrivelled and non-shrivelled Sciros apples indicated that puncture measurements are unreliable when fruit are dehydrated. Puncture measurements suggested shrivelled apples were ‘crisper’ than non-shrivelled fruit, while SENB parameters indicated the reverse.     

Diphenylamine and pre-slicing storage effects on the responses of apple slices to elevated CO2 atmospheres

The effect of treatment with diphenylamine (DPA) and duration of postharvest storage of whole apple fruit on the responses of fresh-cut apple slices to elevated CO₂ storage atmospheres has been investigated. On the day of harvest, ‘McIntosh’, ‘Empire’ and ‘Delicious’ apples were untreated or dipped in DPA, and were held at 0.5 °C overnight or for 6 weeks before slicing. Slices were then stored at 0, 15, 30, 45 or 60% CO₂ in 1% O₂ (balance N₂), atmospheres. Color, firmness and accumulation of acetaldehyde, ethanol and ethyl acetate of the slices were measured. Generally slices were lighter (higher L^* values) when stored in elevated CO₂ atmospheres, but atmosphere and DPA effects varied by cultivar and were affected by pre-slice storage time. Slices prepared from stored fruit were softer compared with slices prepared at harvest. Slice firmness was not affected consistently by CO₂ or DPA concentration, whether they were prepared at harvest or after storage. The effects of increasing CO₂ concentration on acetaldehyde and ethanol accumulations were variable, being affected by cultivar and storage period. DPA treatment did not affect acetaldehyde accumulation of any cultivar, or ethanol accumulation of slices prepared from fruit at harvest. However, DPA-treated ‘Empire’ and ‘Delicious’ apples stored before slicing accumulated less ethanol compared with untreated fruit. Storage of apples before processing increased the accumulation of fermentation volatile compounds by cut apples under storage atmosphere conditions.     

1-甲基环丙烯对苹果低温贮藏期间品质的影响

综述了低温条件下1-甲基环丙烯(1-Methylcyclopropene,1-MCP)贮藏苹果,对其生理代谢及贮藏品质的影响。1-MCP处理可抑制苹果呼吸强度和乙烯释放量,保持较高的可溶性固形物含量,延缓果实硬度的下降,降低了过氧化物酶和多酚氧化酶的活性。低温环境下通过1-MCP处理苹果,其贮藏寿命比常温环境下延长1倍,保持苹果的品质。     

Optical coherence tomography visualizes microstructure of apple peel

Optical coherence tomography (OCT) has emerged recently as a non-destructive technique to visualize subsurface structures of materials. The objective of this work was to investigate whether OCT is an appropriate method to non-destructively assess the peel structural properties of apple fruit and to compare OCT to confocal microscopy and micro-CT. Peel structural properties of apples from different cultivars (‘Braeburn’, ‘Arlet’, ‘Royal Gala’ and ‘Ida Red’) were measured. The effects of preharvest fertilization treatments and storage duration on calculated structural properties of apple peel from OCT images were investigated. It was found that OCT is a fast, high resolution and high field of view technique that renders 2D and 3D images of apple peel. En-face OCT allows the visualization of the surface topology including cracks in the wax, surface roughness and lenticels. Depth scans with OCT reveal the cellular structure down to a few hundreds of micrometre into the fruit, superior to confocal imaging. Spectral-domain OCT resulted in higher quality images than time-domain OCT. Cuticle, epidermis and hypodermis cells can be resolved in a superior way compared to micro-CT. It was concluded that OCT can be used to visualize peel structural differences between apples, as well as to measure structural changes that occur during storage. OCT is a fast method and allows for combining a high depth resolution with a wide lateral image size.     

苹果在模拟运销条件下的质量和生理变化

研究了红星、红富士苹果经过１３０～２４０天贮藏之后，在５种模拟运销条件下的果肉硬度和呼吸动态变化。结果表明，选用优良的贮藏方式，使果实具备良好的贮藏质量是保证果品运销质量的关键；不同品种在运销过程中果肉硬度和呼吸动态变化差异较大，红富士苹果比红星苹果耐运销；冷链运销好于常温运销，常温运销过程中应尽可能保持较低的温度。应当重视研究果实贮后生理和相应的贮后处理技术     

Methods to analyze physico-chemical changes during mango ripening: A multivariate approach

Canonical discriminant analysis (CDA) was used to identify the best method to discriminate between maturity and ripening stages, assessed in terms of dry matter content, firmness, color (peel and flesh), total soluble solids content attributes, before and during ‘Keitt’ mango ripening at 20 °C. Dry matter content was determined by hot-air oven and microwave oven methods. Fruit firmness was determined non-destructively by hand squeezing, with a durometer, using acoustic resonance and low-mass elastic impact methods (AWETA), as well as destructively by the penetrometer. Peel and flesh color were expressed as L*, a*, b*, h⁰ and C* values. Total soluble solids content was analyzed from filtered juice from whole fruit tissue and from unfiltered juice squeezed out by hand. Canonical discriminant analysis indicated that the durometer and the penetrometer were better methods to assess firmness than hand firmness, acoustic resonance or impact methods. The best color attributes to follow changes during early stage of ‘Keitt’ mango ripening were a* and b* values of the flesh, whereas b* value of the peel was considered better during later stages of ripening. Results of total soluble solids content in filtered juice from whole fruit tissue were less variable compared to unfiltered juice squeezed out by hand. Dry matter content was better assessed by drying the sample in a microwave oven than in a hot-air oven. A combined CDA including the best methods to assess each ripening attribute, as well as titratable acidity, showed that the best tools to assess changes in fruit during ripening were the penetrometer, followed by flesh a* value and total soluble solids content (from filtered juice from whole fruit).     

An electronic nose and a mass spectrometry-based electronic nose for assessing apple quality during shelf life

The potential of the electronic nose (E-nose) and the mass spectrometer-based E-nose (MSE-nose) to monitor changes in apple fruit volatiles during shelf life was studied. These techniques were compared with a traditional technique to measure volatiles, gas chromatography combined with mass spectrometry (GC/MS). Apples were stored for 8 months at three different storage conditions and the volatile profile changes were followed subsequently over a period of 15 days. Analysis of the score plot of the principal components analysis for the E-nose measurements showed no storage history effect and only very little shelf life effect. In contrast, the MSE-nose and GC/MS score plots clearly indicated the presence of both shelf life and storage history trend. Moreover, the volatile profile changes during shelf life depended on the storage history. The loading plots of the PCA of the GC/MS data revealed which volatiles are important to differentiate between storage conditions and which ones are important during ripening on the shelf.Partial least square (PLS) models based on the three data sets to relate firmness and days of shelf life with the volatile production of apples were built based on the three data sets. It was found that the models based on the E-nose data had worse prediction performance than those based on the MSE-nose data. Both for firmness (0.95) and days of shelf life (0.98) a high cross-validation correlation was observed between measured and predicted values. The standard error of prediction (S.E.P.) of firmness and shelf life were 2.38×10⁶ Hz² g^2/3 and 1.02 days, respectively. Models based on the GC/MS data showed comparable results.     

Impact of harvesting time and fruit firmness on the tolerance to fungal storage diseases in an apple germplasm collection

Blue mold and bitter rot, caused by Penicillium expansum and Colletotrichum gloeosporioides, respectively, are two of the most devastating diseases during and after storage of apple. The present project was conducted to evaluate the level of tolerance to these diseases in apple germplasm, and investigate possible associations with other fruit characteristics such as harvest date, firmness at harvest, softening (loss of firmness during storage) and sun-exposure. Apples were harvested at a maturation stage suitable for storage, inoculated with spore suspensions of P. expansum (127 cultivars) or C. gloeosporioides (70 cultivars), and stored for 6 or 12 weeks for early- and late-maturing cultivars, respectively. Fruit firmness was measured after harvest and after storage, and the difference was used as a measure of fruit softening. Average lesion diameter varied significantly among both early- and late-maturing cultivars. The amount of damage caused by the two diseases was significantly correlated across cultivars. Regression analyses indicated that lesion diameter was positively affected by fruit softening and negatively affected by harvest date and firmness at harvest. Impact of the independent variables was quantified with partial least squares discriminant analysis; approximately 40% of the genetic variation could be explained by these variables with harvest date being the most important. The effect of sun-exposure was analyzed on six bi-colored cultivars but the results were not conclusive. Cultivars that showed relatively small symptoms in spite of being early-maturing and/or only medium firm, may have other traits that are beneficial for storage and could therefore be especially useful in breeding programs.     

Preharvest calcium applications inhibit some cell wall-modifying enzyme activities and delay cell wall disassembly at commercial harvest of ‘Fuji Kiku-8′ apples

To improve apple firmness during the postharvest chain, detailed knowledge of the biochemistry underlying ripening-related cell wall disassembly, a very complex event, is required. Apple softening is reportedly mediated by calcium loss from the middle lamella, and accordingly calcium applications are expected to preserve fruit firmness. In this work, pre-harvest calcium sprays (7 weekly applications at 1.6%, w/v, 81-123 days after full bloom) were applied to ‘Fuji Kiku-8′ apples, with the purpose of examining treatment effects on cell wall metabolism during on-tree fruit maturation and ripening. Applied calcium improved cell-to-cell adhesion as indicated by better preservation of the middle lamella and by higher contents of ionically bound pectins in treated fruit, leading to higher fruit firmness levels at commercial harvest. Matrix glycan breakdown was also delayed in response to calcium treatment. Calcium applications partially suppressed pectinmethylesterase, pectate lyase, β-galactosidase, α-l-arabinofuranosidase and β-xylosidase activities, without any apparent relationship with ethylene production rates.     

Active label-based packaging to extend the shelf-life of “Calanda” peach fruit: Changes in fruit quality and enzymatic activity

Nectarine fruit after cold storage soften normally, but become dry instead of juicy and can develop flesh browning, bleeding and a gel-like or glassy formation of the flesh near the pit. An experiment was conducted to see if time-resolved reflectance spectroscopy could distinguish these internal disorders non-destructively. The optical parameters of absorption coefficient (μ_a) and reduced scattering coefficient (μ′_s) were measured at 670 nm and 780 nm, on nectarine (Prunus persica cv. Morsiani 90) fruit held at 20 °C after harvest or after 30 d of storage at 0 °C or 4 °C. Each day for 5 d 30 fruit were examined both non-destructively and destructively. Other measurements were firmness with a penetrometer, peel colour on the blush and non-blush side, expressible juice, weight loss, and visual rating of internal browning, bleeding, and gel. The fruit had been sorted at harvest according to the value of μ_a670 so that each batch had a similar spread of fruit maturity. More mature fruit (lower μ_a670 values) developed internal browning and bleeding with more severe symptoms compared to less mature ones (higher μ_a670 values). It was found that μ_a780 could distinguish healthy fruits from the chilling injured ones. Canonical discriminant analysis indicated that fruit without cold storage had low μ_a780, less water loss, low firmness, but high μ_a670 and high expressible juice compared with cool stored fruit. Fruit cool stored at 4 °C had high μ_a780 and less expressible juice, lower water loss and lower firmness compared with fruit cool stored at 0 °C. It was concluded that time resolved reflectance spectroscopy could detect internal woolliness and internal browning in nectarines after storage.     

Hyperspectral laser-induced fluorescence imaging for assessing apple fruit quality

Chlorophyll fluorescence is a promising technique for postharvest quality research, and reported studies were mainly based on the fluorescence kinetic analysis method, which has not been quite satisfactory for measuring fruit quality. This paper reports on using a hyperspectral imaging technique for measurement of laser-induced fluorescence from apple fruit for predicting multiple fruit quality parameters. A continuous wave blue laser (408 nm) was used as an excitation source for inducing fluorescence in apples. Fluorescence scattering images were acquired from ‘Golden Delicious’ apples by a hyperspectral imaging system at the instance of laser illumination (0 min) and after 1, 2, 3, 4, and 5 min of illumination. The hyperspectral fluorescence image data were represented by mean, maximum, and standard deviation spectra. Standard tests were performed on measuring fruit skin and flesh color, firmness, soluble solids content, and titratable acid. A hybrid method of combining principal component analysis and neural network modeling was used for developing prediction models to predict fruit quality parameters for each of the six illumination time periods. Fluorescence emission decreased steadily during the first 3 min of illumination and was stable within 5 min. The 0-min fluorescence prediction models had somewhat poorer prediction results for individual quality parameters except skin hue than did the models of longer illumination time. The differences were minimal in the model prediction results from the fluorescence data at 1, 2, 3, 4 or 5 min of illumination. Overall, excellent predictions were obtained for apple skin hue with the correlation coefficient of prediction of 0.94. Relatively good predictions were obtained for fruit firmness, skin chroma, and flesh hue with values for the correlation coefficient being equal to or greater than 0.74 for 1 min of illumination or longer times, and poorer correlations were found for soluble solids content, titratable acid, and flesh chroma. Hyperspectral laser-induced fluorescence imaging is potentially useful for assessing selected quality parameters of apple fruit and further research is needed to improve fluorescence measurement for better prediction of fruit quality.     

1-MCP处理对不同贮藏设施条件下富士苹果保鲜效果的影响

以富士苹果为试材,研究了不同贮藏设施(大型恒温冷库、小型组装式恒温贮藏库、改造土窑洞、传统土窑洞)条件下1-MCP处理对富士苹果采后生理特性和贮藏品质的影响。结果表明,富士苹果属呼吸跃变型果实,在四种不同贮藏设施条件下,1-MCP处理均可明显降低贮藏期间果实的呼吸速率和乙烯释放速率,较好地保持果实硬度和可滴定酸含量,且贮藏设施条件越好,1-MCP的处理效果越明显。但果实的可溶性固形物含量有所降低,可能是1-MCP处理延缓了果实的后熟、成熟度较低的缘故。     

Measuring consumer response to ‘Gala’ apples treated with 1-methylcyclopropene (1-MCP)

Post-harvest apple treatment with 1-methylcyclopropene (1-MCP) was previously found to inhibit fruit ripening but also to inhibit the production of volatile compounds that contribute to apple flavor. The first objective of this study was to determine if consumers could distinguish 1-MCP treated and untreated Gala apples [Malus sylvestris L. (Mill.) var. domestica Borkh. Mansf.] following long-term storage. Chemical analysis showed 1-MCP treated fruit had reduced flavor volatiles compared to untreated fruit. Consumer difference tests showed they could distinguish between 1-MCP treated and untreated fruit. A second objective was to compare consumers’ acceptance for 1-MCP treated to untreated apples. Both 1-MCP treated and untreated apples received high overall liking scores that were not significantly different. Equal numbers of consumers indicated preference for 1-MCP treated and untreated fruit and there was no difference in purchase intent. However, subsets of consumers who eat Gala, Fuji or Red Delicious apples showed preference for untreated over 1-MCP treated fruit compared to consumers who do not eat these varieties.     

Delaying establishment of controlled atmosphere or CO2 exposure reduces ‘Fuji’ apple CO2 injury without excessive fruit quality loss

Storage of ‘Fuji’ apple fruit in a high CO₂ (3 kPa) and low O₂ (1.5 kPa) controlled atmosphere (CA) reduced firmness and titratable acidity (TA) loss during long term storage. This CA environment also induced development of internal CO₂-injury (brown-heart) and slowed the disappearance of watercore. The symptoms of internal CO₂-injury were first detected 15 days after CA establishment and the severity increased during the first 4 months of CA-storage. Delaying establishment of CA conditions for 2–12 weeks significantly reduced the severity of CO₂-injury. Delaying CO₂ accumulation to 3 kPa for 1–4 months during CA (1.5 kPa O₂+0.05 kPa CO₂) storage also reduced development of CO₂-injury symptoms. Delaying CA or CO₂ accumulation resulted in lower firmness and TA compared to establishment of CA within 72 h of harvest. However, the delay treatments did result in firmness and TA that were significantly higher compared to values for fruit stored in air. The incidence and severity of senescent injuries (flesh browning and core flush) detected during the late period of storage were greater in air- than CA-stored fruit. The results indicate the susceptibility of ‘Fuji’ apples to CO₂-injury is highest during the first weeks of storage after harvest. Delaying establishment of CA or exposure to elevated CO₂ after harvest may be a practical strategy to reduce CO₂-injury while maintaining other important quality attributes at acceptable levels.