Cox's Orange Research Articles

Exposure to hypoxia conditions alters volatile concentrations of apple cultivars

Brief periods of hypoxia at ambient temperatures (20 °C) have potential for disinfestation treatments or as pre-treatments to maintain fruit quality during extended storage. Nine cultivars of apple (Cox's Orange Pippin, Fuji, Golden Delicious, Granny Smith, Pacific Rose, Red Delicious, Royal Gala, Splendour and Southern Snap) were exposed to hypoxia using an atmosphere of 100% carbon dioxide for 24 h at 20 °C. Quantitative and qualitative analyses of volatile compounds were undertaken after removal of fruits from a high-carbon-dioxide atmosphere and during 1 week at 20 °C. Concentrations of acetaldehdye, ethanol, ethyl acetate and ethyl esters were consistently enhanced by hypoxia, while concentrations of acetate esters and aldehydes were depressed. Cultivars varied considerably in response to high carbon dioxide, with Cox's Orange Pippin and Golden Delicious having the least and Fuji and Red Delicious the greatest enhancement in ethyl esters. Fruits exposed to hypoxia had larger odour unit scores than control fruits, suggesting that such changes in volatile concentration may affect aroma and/or flavour. Enhanced ethyl ester concentrations in fruits exposed to hypoxia may be due to increases in ethanol concentration that competitively inhibit formation of non-ethyl esters. There may also have been a change in ester-forming enzyme activity and/or substrate specificity of the volatile biosynthetic pathway. This study has shown that short-term exposure to hypoxia has the potential to change the aroma/flavour of apples. © 2000 Society of Chemical Industry

Carbohydrate composition and content of organic acids in fresh and stored apples

The contents of low-molecular-weight carbohydrates (LMWC; sorbitol, glucose, fructose and sucrose), starch, dietary fibre and organic acids were determined in seven apple cultivars at the start and end of the consumption interval. The cultivars included were Summered, Aroma, Ingrid Marie, Cox Orange, Mutzu, Belle de Boskoop and Jonagold. The total content of LMWC ranged between 615 and 716 g kg−1 dry matter (DM). The dominating sugar was fructose, corresponding to on average 57% (range 48–62%) of the total LMWC. However, in Cox Orange the sucrose content was considerably higher and the fructose and sucrose contents constituted approximately 46% each. Total dietary fibre content was similar in the cultivars (total dietary fibre 160 ± 20 g kg−1 DM), except for Belle de Boskoop which had a higher content (203 g kg−1 DM). Mutzu had a lower proportion of soluble fibre (27% of total dietary fibre) compared with the others (mean 32%). The organic acid content was on average 80 ± 4 g kg−1 DM, except for two of the cultivars (Summered and Belle de Boskoop) which had a higher content (105 ± 6 g kg−1 DM). Interestingly, the organic acid content was only slightly reduced upon storage in the case of Belle de Boskoop, whereas there was a substantial decrease in all the other cultivars (p < 0.001). Sucrose (p < 0.01) and starch (p < 0.05) contents decreased in all cultivars following storage, whereas sorbitol (p < 0.05) and total dietary fibre (p < 0.05) contents increased. It is concluded that the observed differences in composition are of such magnitude that they may affect both nutritional and sensory properties. © 2000 Society of Chemical Industry

Cryopreservation of Cold-tender Apple Germplasm

Unlike cold-hardy apple germplasm, dormant vegetative buds from cold-tender accessions require stabilization of meristematic tissue to protect against injury during desiccation and cryopreservation. Dormant buds of six apple cultivars [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Cox's Orange Pippin', `Einshemer', `Golden Delicious', `Jonagold', `K-14', and `Mutsu'] collected at specific intervals in 1993, 1994, and 1995 at Geneva, N.Y., were stabilized by encapsulation in 5% alginate, treated with step-wise imbibition of 0.5 to 1.0 m sucrose and 0.2 m raffinose solution, and desiccated with forced air at 0 °C. Sugar-alginate stabilization reduced injury during desiccation, increased cold-hardiness of the six cold-tender cultivars frozen to -30 °C, and improved recovery following cryopreservation of buds collected before optimal cold acclimation was attained. Sucrose tissue levels did not increase following stabilization treatment, but levels of glucose and fructose, and of an unknown disaccharide increased. This procedure used nontoxic cryoprotectants, and has potential to expand the scope of dormant bud cryopreservation to include cold-tender apple germplasm.

Electron-energy-loss spectroscopic imaging of calcium and nitrogen in the cell walls of apple fruits

Changes in texture are an integral part of ripening in most fleshy fruits and these changes are thought to be determined, primarily, by alterations in cell wall structure. Electron energy loss spectroscopy (EELS) imaging was used to obtain quantitative information on the levels of calcium and nitrogen in the cell walls of apple (Malus domestica Borkh. cv. Cox's Orange Pippin) fruits. Samples of fruit cortex were prepared for EELS by high-pressure freezing and molecular distillation drying to minimize loss and redistribution of soluble cell wall components such as calcium. The EELS imaging successfully resolved calcium and nitrogen levels in the middle lamella and primary cell wall. When the elemental compositions of the cell walls of Cox's apples from two sites in the UK were compared at harvest or after 6 months storage, the orchard which always produced consistently firmer fruit had significantly lower levels of cell wall calcium and higher levels of cell wall nitrogen. This result was unexpected since firm texture in apples and other fruits has been commonly associated with elevated levels of fruit calcium. The nitrogen-rich material in the sections used for EELS was insoluble in acidified methanol, indicating that it represented a high-molecular-weight component in the cell wall. Furthermore, total tissue hydroxyproline levels were greatest in material with elevated cell wall nitrogen, suggesting enhanced levels of wall structural proteins in the tissue. These data indicate a correlation between increased amounts of cell wall nitrogen and firm fruit texture. The possible role of cell wall proteins in determining the textural properties of fruit tissue is discussed.

PREHARVEST FACTORS AND POSTHARVEST QUALITY DECLINE OF APPLES

Two types of experiment were conducted to identify preharvest factors that might be correlated with fruit quality at harvest and rate of postharvest loss of quality. The research was planned as a first step towards predicting the loss of quality in terms of firmness, green ground colour, acid- and soluble solids concentration. The first, inventory experiment involved a large number of orchards of 'Cox's Orange Pippin', 'Elstar', 'Red Boskoop' and 'Jonagold', all on M9 rootstock. Samples for chemical fruit analysis were taken 3 weeks before harvest and at harvest. Fruit for quality measurements were collected at harvest and after storage and shelf life. In the second experiment, N, P, K, Ca and Mg were applied, each at 5 levels, in a new orchard planted with 'Elstar' on M.9 to create fruit with different concentrations of these nutrients in order to study the relationship with post-harvest quality development. Fruit firmness at harvest was negatively correlated with fruit nitrogen level in August and at harvest and (in 'Elstar') with leaf nitrogen level in June and July. Green ground colour was (at least in 'Elstar') correlated positively with leaf and fruit nitrogen level in June, July and August, but not in September. Acid concentration was highly correlated with fruit K and Mg levels and with fruit weight at harvest. In 'Elstar', total soluble solids content was correlated positively with leaf P level and % of dry matter. Following storage and shelf life, the level of fruit characteristics was generally best correlated with the level at harvest. To a smaller extent significant correlation was observed with nutrients that did not correlate significantly with the level at harvest (e.g. P and Mg with firmness). The correlation between acid concentration and fruit K and Mg concentration, already high at harvest, was even higher after storage. Multiple regression models explaining the loss of firmness during storage and shelf life had a better % of variance accounted for than those explaining the absolute level at any moment. These first results are discussed in physiological terms and with respect to their possible significance for cultural practice and for prediction of fruit quality.

Orchard comparisons of `Cox's Orange Pippin' grown on selections of the apple rootstock M.9

SummaryTwenty four selections (clones) of M.9 were compared as rootstocks for the apple cv. Cox's Orange Pippin in three orchard trials planted on similar sites at Horticulture Research International (HRI)-East Malling between 1980 and 1987. Rootstock clone effects on maiden tree quality were inconsistent in two of the trials, and appeared to be associated more with nursery conditions at the time of raising the trees than with the clone of rootstock used. Shoot growth following planting in the orchard was related positively to tree size (maiden tree height and feathering) at the time of planting and no differences in initial tree vigour were attributable to rootstock clone. Tree size differences at maturity were variable between trials, were small (10% to 30%), and in most instances not statistically significant. Nevertheless, the scion weights of trees on the Dutch T.337, the French INRA 71/0 and Lancep (Pajam 1) rootstock clones were 10% to 30% smaller than trees on the EMLA clone when the trials were terminated. None of the clones had any consistent effect on the precocity of flowering, the numbers of floral buds produced by the trees, or the efficiency of fruit set. In two of the three trials, annual yields and cumulative yields per tree were very similar for trees on all the M.9 clones, even when adjusted for differences in tree size at planting. Estimates of yield efficiency in each year (yield in kg cm22 trunk cross sectional area) also showed no statistically significant differences between any of the M.9 clones in these two trials. In a third trial, yield precocity in the first three cropping years was much lower than average for trees on the Belgian clone Nic.29, the French clone INRA 71/0 and the German clone SP.1 (719), even after adjustments to take account of differences in tree size at planting. Trees on the Dutch selection T.340, the Belgian selections Nic.16 and Nic.19 the German selection SP.18 (751) and M.9A also showed reduced yield efficiency compared with trees on the EMLA clone in two of these three years. No differences were recorded in the mean fruit size at harvest or the yield of fruits in the highest quality grades in this third trial.

Apple rootstock studies: Comparison of Polish, Russian, USA and UK selections as rootstocks for the apple cultivar Cox's Orange Pippin (Malus domestica Borkh.)

SummaryEleven apple rootstocks, originating in Poland, Russia, the USA and the UK, were evaluated for the scion cv. Cox's Orange Pippin (`Cox'), grown without supplementary irrigation in south-east England. Two of the rootstocks, B.146 and P.22, produced trees that were more dwarfed, suckered more and bore fruit smaller than those on trees on M.27–EMLA. Trees on P.2 were intermediate in vigour between those on M.27–EMLA and those on M.9–EMLA and these trees exhibited good yield precocity and yield efficiency. `Cox' trees on P.16, MAC.9, B.9 and M.9–EMLA were similar in vigour. Although trees on P.16, MAC.9 and B.9 rootstocks induced good yield precocity and efficiency (yield per unit tree crown volume) and produced fruits of good size and quality, none of these rootstocks was considered superior to M.9-EMLA. Trees on MM.111, which were of intermediate vigour, performed slightly better in terms of yield efficiency than trees on MM.106 and much better than trees on P.18.

Effect of interstock bridge grafting (M9 dwarfing rootstock and same cultivar cutting) on vegetative growth, reproductive growth and carbohydrate composition of mature apple trees

Four apple cultivars, Granny Smith, Cox's Orange, Gala and Oregon Red Delicious on rootstock MM106, M793 or Northern Spy were interstock bridge grafted with M9 dwarfing rootstock or same cultivar cuttings to investigate the effect on vegetative, reproductive and biochemical changes and fruit quality at harvest in different apple cultivars. Controls were also left with no interstock treatment. In general bridge grafting reduced shoot growth (up to 20%), increased floriferousness, changed carbohydrate (CHO) level and increased yield (up to 30%) with the greatest effects in the second season. The treatment did not significantly change mean fruit weight, fruit length to diameter (L/D) ratio or flesh colour in first season, while in the second season there were significant differences in these apple quality measures. Seed number and brix value at harvest from both treatments were significantly increased in both seasons. Flesh firmness also showed significant increases in both seasons. The M9 bridge and same cultivar interstocks were generally similar in effect though occasionally the M9 had a greater effect. Interstock bridge grafting of mature apple trees may be a viable method of reducing growth and improving yield.

COMPARISON BETWEEN SENSORY AND INSTRUMENTAL MEASUREMENTS FOR MEALINESS ASSESSMENT IN APPLES. A COLLABORATIVE TEST

ABSTRACTDefinition and establishment of assessment procedures for mealiness of apple fruits using sensory and instrumental measurements were performed on ‘Boskoop', ‘Cox's Orange Pippin’ and ‘Jonagold’ samples with varying degrees of mealiness. The sensory procedure profiled mealiness as a loss of crispness, hardness, and juiciness, with an increase in the floury sensation in the mouth. High correlations between the sensory descriptors and instrumental parameters was shown through principal component analysis. The instrumental procedures (confined compression of fruit cylinders and acoustic impulse response) gave coefficients of determination for juiciness and crispness of 0.85 and 0.71, respectively. This level of accuracy indicates the possibility of establishing

Microscopic observation of mealiness in apples: a quantative approach

Abstract Mealiness is a quality characteristic that is used to describe fruit which is soft and which causes a dry feeling in the mouth during mastication. The purpose of this work was to visualise the difference between fresh and mealy apples and to quantify those differences. Three commercially important Belgian apple cultivars, `Jonagold', `Cox's Orange Pippin' and `Boskoop' apples ( Malus domestica Borkh.) were used in the experiments. Mealy apples were produced by holding apples at 20°C and 95% RH for periods of time depending on the cultivar and the required mealiness level. Images were made with a light microscope. Cell parameters such as area and perimeter, and two roundness parameters were measured. `Cox's Orange Pippin' and `Boskoop' apples could be separated into the two groups: fresh and mealy, using the four calculated cell parameters. The number of broken and intact cells at the rupture surface of a fractured tissue sample after tensile loading was also calculated. After one week's storage of fruit in mealiness-inducing conditions, the amount of broken cells at the surface of a fractured sample was significantly lower than in fresh apples.

Temperature and irrigation effects on the cropping, development and quality of `Cox's Orange Pippin' and `Queen Cox' apples

The cropping and growth of apple fruit of `Cox's Orange Pippin' and `Queen Cox' trees was investigated in relation to temperature and irrigation in an orchard at East Malling in Kent, UK. The air temperature surrounding a block of orchard trees was elevated by enclosing in a polythene tunnel from bloom in May until harvest in early September; throughout this period the trees were irrigated. A second block of trees was covered partially with a polythene tunnel, with the intention of providing a similar light regime as in the complete polytunnel, but without raising the temperature. To examine the effects of irrigation, some trees outside the polytunnels received irrigation while others did not. Detailed continuous measurements of the canopy climate, particularly temperature, were made until harvest. Throughout the growing season, fruit size was measured repeatedly and non-destructively to calculate fruit volume and fruit growth rates. The largest `Cox' and `Queen Cox' fruits were obtained from the trees grown in the complete polytunnel with irrigation, where the higher temperature was associated with fewer fruit being retained and the individual fruit growing more than those at the lower temperature. Fruit on trees in the partial tunnel with irrigation, and outside with irrigation, were similar in size. The smallest fruit were produced on the non-irrigated trees outside. The mean cortical cell area of the `Cox' fruit from non-irrigated trees outside was not significantly smaller than that from either the outside irrigated (OI) or the polytunnel-grown (PT) fruits: despite this, differences in cell area, rather than cell number, were a more likely explanation for the effects of temperature or irrigation on final fruit size. The increases in fruit size were associated with a greater loss of fruit texture and quality during storage than in smaller fruit from non-irrigated trees.

FRUIT PHOTOSYNTHESIS AND POME FRUIT QUALITY

Fruit taste in terms of fruit quality is dominated by the sugar:acid ratio. Photosynthesis and carbon metabolism of fruit differ from that of leaves in that organic acids contribute to the carbon storage pool despite starch and sugar. Malic acid is the predominant organic acid in pome fruits, induces their acidic taste and is produced by a two-step enzymic reaction. It involves the synthesis of (1) the instable oxaloacetic acid (OAA) by phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) or phosphoenolpyruvate carboxykinase (PCk; EC 4.1.1.49), and (2) malic acid by malic dehydrogenase (MDH). These enzymes were purified from apple fruit cvs 'Golden Delicious'and 'Cox's Orange Pippin' at Long Ashton, University of Bristol, England. This collaborative work has shown that the CO 2 concentrating mechanism by PEPC and the kinetic properties of apple fruit PEPC, both resulting in malic acid synthesis, suggests the definition of a new type of 'fruit photosynthesis' rather than its categorisation within an existing type. The activity of MDH extracted from apple fruit was ca. 80fold in excess of that of PEPC, leaving the regulation largely at the PEPC level. Regulation of malic acid synthesis is by glucose-6-phosphate stimulation and end product inhibition of PEPC by malic acid in a strongly pH-dependent manner. PEPC had a pH optimum at pH 7.8 and was salt-sensitive at concentrations above 160 mM salt. PEPC exhibited a Ki of between 10 μM at pH 6.8 and 46 mM L-malate at pH 8. This mechanism also provides fine regulation of cytoplasmic pH in pome fruit.

APPLE YIELD AND QUALITY AS AFFECTED BY TRAINING AND SHADING

Fruit yield and quality were investigated on five-year-old apple trees (Malus domestica Borkh. cv. Cox's Orange Pippin) on M9 rootstocks growing in field lysimeters, as affected by training to Y-trellis or slender spindle at full light exposure or 60 % shading treatment in the fourth growing season after planting. In comparison with the spindles and shaded trees, Y-trellis and exposed ones bore more fruits and got higher fruit yield with heavier average fruit weight and larger fruit size. Contents of dry matter, total soluble solids, the solids/acid ratio, starch, glucose, fructose, sucrose, sorbitol and total non-structural carbohydrates were higher in fruits from Y-trellis and exposed trees than those from the spindles and shaded ones. In addition, shading treatment increased N, P, K and Mg contents and K/Ca ratio, especially in K and Mg, but tendenciously decreased Ca content of fruits. Incidences of physiological disorder and fungi diseases of fruits during five months' storage were lower from shaded trees and the spindles than those from exposed and Y-trellis trees.

Temperature Affects Postharvest Color Change of Apples

Loss of green color (yellowing) in apples (Malus ×domestica Borkh.) is due to chlorophyll breakdown, an enzyme-mediated reaction conforming to first-order kinetics. Nondestructive measurements of yellowing, using a tristimulus chromameter, were related to chlorophyll content for `Cox's Orange Pippin' and `Granny Smith' apples stored at temperatures of 0 to 35 °C. Yellowing determined by rate constant (k) of total chlorophyll and changes in hue angle, as a function of temperature, increased slowly from 0 to 5 °C, increased exponentially from 5 to 20 °C, reached a maximum from 20 to 24 °C, then declined at higher temperatures. Values of k and the rate of change of hue angle were characterized by a modified Arrhenius equation. `Cox's Orange Pippin' apples harvested early had lower k and lower rates of hue angle change than late-harvested fruit. Values of k and hue angle change of `Granny Smith' apples differed between years but not between harvests. The method used to characterize the relationship between yellowing and temperature may describe changes in other important quality attributes of apple fruit during storage and shelf life and help evaluate the efficacy of cool-chain handling and storage systems.

Effect of carbon dioxide on the internal lower oxygen limits of apple fruit

The effect of elevated CO2 between 0 and 8 kPa on steady-state lower O2 limits based on internal atmospheres (LOLi) was estimated for postclimacteric `Cox's Orange Pippin' and `Braeburn' apples at 0 and 20°C. Two types of LOLi were estimated: the anaerobic compensation point (ACPi), and the internal fermentation threshold based either on the respiratory quotient (FTiRQ) or ethanol (EtOH) accumulation (FTiEtOH). ACPi, for both cultivars and temperatures, remained constant at 0.5 kPa O2 for `Cox's Orange Pippin' and 0.8–1.0 O2 for `Braeburn' apples for levels of CO2 external to the fruit between 0 and 8 kPa. However, for FTiRQ and FTiEtOH, no consistent trend with level of CO2 was evident at 20°C for either cultivar. In contrast, at 0°C FTiRQ and FTiEtOH were 0.2–0.8 kPa O2 higher at 8 kPa CO2 than at 0 kPa CO2 (with the exception of FTiRQ for `Cox's Orange Pippin'). A small decrease in O2 uptake (estimated from the difference in external and internal O2 atmospheres) was observed between 2 and 8 kPa CO2 at 20°C. Elevated CO2 slightly lowered the respiratory quotient (RQi, estimated from the ratio of differences between external and internal atmosphere partial pressures of CO2 and O2) of `Cox's Orange Pippin' in 8 kPa CO2 and `Braeburn' in 2 to 8 kPa CO2 at 20°C, and more markedly in 8 kPa CO2 at 0°C. The RQi of `Cox's Orange Pippin' and `Braeburn' apples was slightly and markedly higher respectively at 0°C compared to 20°C. The lower RQi of `Braeburn' at 20°C compared to `Cox's Orange Pippin' apples indicated `Braeburn' had a higher permeance to CO2 relative to O2 compared to `Cox's Orange Pippin'. This study indicates the tolerance of `Cox's Orange Pippin' and `Braeburn' apples to low O2 levels may be affected by levels of CO2.

Temperature effects on the internal lower oxygen limits of apple fruit

Abstract Exposure of packaged fresh produce in modified atmospheres (MA) to elevated temperatures can cause the partial pressure of oxygen inside the produce (PO2i) to fall below internal lower O2 limits (LOLis), resulting in fermentation and loss of quality. In this study, two types of LOLi were estimated from steady-state external chamber atmospheres: the anaerobic compensation point (ACPi), and the fermentation threshold based on the respiratory quotient (FTRQi) and on ethanol (EtOH) accumulation (FTEtOHi). Mean estimates of LOLis of apple cultivars ‘Cox's Orange Pippin’ and ‘Braeburn’ ranged between 0.5 and 1.0 kPa internal partial pressure of O2 (pO2i for ACPi; 0.8 and 1.7 kPa pO2i for FTRQi, and 0.5 and 2.0 kPa pO2i for FTEtOHi, for fruit temperatures between 0 ° and 28 °C. Values for ACPi estimated at 32 °C were higher than those between 0 ° and 28 °C. In general, estimates of dissolved O2 concentration at ACPi and FTRQi tended to decrease with increasing temperature for ‘Braeburn’ apples, changed little for ‘Cox's Orange Pippin’ apples, but increased again for ACPi at 32 °C. On average, estimates of LOLis were higher for ‘Braeburn’ than ‘Cox's Orange Pippin’ apples. The effect of temperature on diffusion coefficients and solubility were considered unlikely to contribute significantly to variation in LOLis except for solubility at higher temperatures, but differences in tissue porosity may have influenced differences in LOLis between cultivars. Results of the current study indicate temperature effects on LOLis would not be significant except for MA packages destined for markets with ambient temperatures in excess of 28 °C. On the other hand it seems that to assume that ACPi is independent of temperature may be too simplistic, particularly if fruit are exposed to a very wide range of temperatures. LOLis were relatively constant compared with lower O2 limits based on package atmospheres, and can be used to estimate optimum MA package atmospheres that account for fruit within a population with the highest respiration rates and lowest permeance to O2.

Up‐regulation of two cDNA clones encoding metallothionein‐like proteins in apple fruit during cool storage

We are investigating the molecular basis of low temperature responses in apples, by identifying and characterising fruit genes which show altered expression in response to cool‐storage, Two independent cold‐regulated clones (pAMTI and pAMT2) were isolated from a cDNA library derived from cool‐stored apple (Malus domestics Borkh. cv. Granny Smith) fruit. These clones share only 27% amino acid identity with each other, but both show high similarity to plant metallothionein (MT)‐like proteins. The polypeptide encoded by pAMTI shares similarity with type 2 MT‐like sequences, while that encoded by pAMT2 is similar to others which share a different distribution of cysteine residues. We suggest, these form a ‘type 3’ group of MT‐like clones. Genomic Southern analysis confirmed that there is a family of MT‐like genes in apple. There are differing patterns of pAMTI and pAMT2 expression during apple fruit development, amt 1 RNA was abundant in flowers and during the early stages of development, and decreased as the fruit approached maturity, while amt2 RNA was barely detectable in flowers and young fruit and accumulated with fruit development. In ripe fruit. amt 1. expression was up‐regulated, while amt2 expression was down‐regulated. In leaves, both genes showed increased expression with leaf age. In Granny Smith, Cox's Orange Pippin and Braeburn apple cultivars. both genes were up‐regulated in cool‐stored fruit. In Granny Smith contical tissue, amt RNA levels were elevated within the first 45 min at both 0.5°C and 4°C, but not at 12.5°C. The different patterns of amt1 and amt2 expression during fruit development and in different tissues suggest that the respective genes have distinct controlling elements and may be functionally different. The in vivo roles of the encoded polypeptides, particularly in relation to chilling tolerance or acclimation, are as yet unknown.

Studies on Apple Bruising: II. The Effects of Fruit Characteristics, Harvest Date and Precooling on Bruise Susceptibility of Three Apple Cultivars

Abstract The effect of harvest dates, precooling and fruit characteristics on the bruise occurrence in three apple cultivars (Aroma, Cox's Orange Pippin, Ingrid Marie) have been studied. Bruise weight percentage (BWP) increased by delayed harvest in Aroma and Ingrid Marie but did not affect fruits of Cox's Orange Pippin. Fruits of the bruising sensitive cultivars, Aroma and Ingrid Marie, responded positively to precooling, whereas Cox's Orange Pippin did not. No relationships were noted between storage conditions, fruit firmness, colour and bruise. Large fruits bruised more than small fruits

Studies on Apple Bruising: I. Estimation of Incidence and Susceptibility Differences in the Bruising of Three Apple Cultivars

Abstract Bruising in “Aroma”, “Cox's Orange Pippin” and “Ingrid Marie” apples grown in a Swedish research orchard were studied during two seasons—1992, 1993. Incidence was recorded by dropping fruits from 0, 5, 10, 15, 25 and 30 cm. Bruising increased with increasing drop heights, and dropping from higher than 10 cm caused more large bruise areas. The diameter of some bruise areas increased during storage for 2 months. Aroma was the more sensitive cultivar and Cox's Orange Pippin was the more resistive against bruising. In order to compare bruise quantifying methods, we studied number, diameter, weight and volume of bruise. We found that the bruise weight parameter ((bruise weight/fruit weight) × 100) was the most accurate method owing to the correspondence between this parameter and impact energy.

Changes in respiration and ethylene production of apples in response to internal and external oxygen partial pressures

Variations in respiration rate and ethylene production of ‘Cox's Orange Pippin’ and ‘Granny Smith’ apples in response to reduced oxygen partial pressures were characterised by studying O2, CO2 and C2H4 partial pressure differences between the internal and external atmospheres (ΔpO2, ΔpCO2 and ΔpC2H4, Pa) of individual fruit maintained in different O2 atmospheres at 20 ± 1°C. ΔpO2 decreased at low O2 levels, reflecting the decreased rate of O2 uptake in low O2 partial pressures. Oxygen uptake relative to that in air (relrO2) approximately followed Michaelis-Menten kinetics, with a half-maximal rate at 3.3 kPa O2 for internal oxygen (piO2) and 10.4 kPa O2 for external oxygen (peO2). An equation was developed to describe aerobic and anaerobic components of CO2 production relative to that in air (relrCO2) as a function of peO2 or piO2. The relationship between rate of C2H4 production relative to that in air (relrC2H4) and piO2 was reasonably described by a Michaelis-Menten type hyperbolic curve, confirming the expectation that small changes in O2 partial pressure would have a much greater effect on relrC2H4 at low piO2 than they do at high piO2. In contrast, presence of the skin as a diffusion barrier resulted in development of an apparent ‘lag phase’ in the relationship between relrC2H4 and peO2 such that it became essentially sigmoidal. These differences are attributed to differences in O2 partial pressure between internal and external atmospheres.