Performance of an Expert Sensory Panel and Instrumental Measures for Assessing Eating Fruit Quality Attributes in a Pear Breeding Programme.

Breeding programmes count on stable trained panels that support breeding evaluation selections. This work aimed to evaluate the performance of a small expert panel in the join IRTA-PFR breeding programme to validate its use in the sensory assessments of fruit pear genotypes during the selection process. A breeding F1 population of 80 pear seedlings from this programme was used. Descriptors and standard references used for sensory evaluations of pear attributes were previously defined by the four members of the expert panel. A General Procrustes Analysis (GPA) was applied to analyse the relations between instrumental and sensory traits. The results showed a good relationship between sensory attributes such as firmness and crispness with penetrometer measures. A high correlation was also found between sensory sourness and titratable acidity (TA). Panel performance was evaluated in terms of reproducibility, homogeneity, and panel consonance. The results indicated that the experts were very consistent and had a good performance. The work demonstrates, for the first time, that a small expert trained panel could be efficiently used in pear breeding programmes and allows for the selection process in a more economical and available way in contrast to the larger sensory panels conventionally used.

ROS-scavenging-associated transcriptional and biochemical shifts during nectarine fruit development and ripening.

ROS are known as toxic by-products but also as important signaling molecules playing a key role in fruit development and ripening. To counteract the negative effects of ROS, plants and fruit own multiple ROS-scavenging mechanisms aiming to ensure a balanced ROS homeostasis. In the present study, changes in specific ROS (i.e. H2O2) as well as enzymatic (SOD, CAT, POX, APX) and non-enzymatic (phenylpropanoids, carotenoids and ascorbate) ROS-scavenging systems were investigated along four different stages of nectarine (cv. 'Diamond Ray') fruit development and ripening (39, 70, 94 and 121 DAFB) both at the metabolic (28 individual metabolites or enzymes) and transcriptional level (24 genes). Overall, our results demonstrate a complex ROS-related transcriptome and metabolome reprogramming during fruit development and ripening. At earlier fruit developmental stages an increase on the respiration rate is likely triggering an oxidative burst and resulting in the activation of specific ethylene response factors (ERF1). In turn, ROS-responsive genes or the biosynthesis of specific antioxidant compounds (i.e. phenylpropanoids) were highly expressed or accumulated at earlier fruit developmental stages (39-70 DAFB). Nonetheless, as the fruit develops, the decrease in the fruit respiration rate and the reduction of ERF1 genes leads to lower levels of most non-enzymatic antioxidants and higher accumulation of H2O2. Based on available literature and the observed accumulation dynamics of H2O2, it is anticipated that this compound may not only be a by-product of ROS-scavenging but also a signaling molecule accumulated during the ripening of nectarine fruit.

Elucidating the involvement of ethylene and oxidative stress during on- and off-tree ripening of two pear cultivars with different ripening patterns.

Scarce information is available about the ripening process of European pears attached and detached from the tree. Accordingly, this study aimed to investigate the physiological and biochemical processes underlying both on- and off-tree fruit ripening in a summer ('Conference') vs. a winter ('Flor d'Hivern') pear cultivar. For each cultivar, a batch of fruit was harvested at the commercial harvest date and ripened at 20 °C and another batch was left to ripen on the tree. In both cultivars the inability of the fruit to soften on-tree, was related to a very limited ethylene metabolism but also associated to high content of H2O2 and low lipid peroxidation levels. In contrast, ripening in detached fruit was cultivar-dependent. In 'Conference' pears, the sharp firmness loss and colour changes observed during off-tree ripening were not strictly associated to an enhanced ethylene production but rather triggered by an oxidative related process preceding the climacteric rise. In contrast, 'Flor d'Hivern' pears experienced limited softening and degreening during off-tree ripening not being related to the action of ethylene or oxidative stress. Collectively our results showed that pear ripening was not exclusively dependent of ethylene production and that the fruit potential to limit oxidative damage may be involved with the inability of some European pear cultivars to ripen on-tree.

Investigation of the transcriptomic and metabolic changes associated with superficial scald physiology impaired by lovastatin and 1-methylcyclopropene in pear fruit (cv. "Blanquilla").

To elucidate the physiology underlying the development of superficial scald in pears, susceptible "Blanquilla" fruit was treated with different compounds that either promoted (ethylene) or repressed (1-methylcyclopropene and lovastatin) the incidence of this disorder after 4 months of cold storage. Our data show that scald was negligible for the fruit treated with 1-methylcyclopropene or lovastatin, but highly manifested in untreated (78% incidence) or ethylene-treated fruit (97% incidence). The comparison between the fruit metabolomic profile and transcriptome evidenced a distinct reprogramming associated with each treatment. In all treated samples, cold storage led to an activation of a cold-acclimation-resistance mechanism, including the biosynthesis of very-long-chain fatty acids, which was especially evident in 1-methylcyclopropane-treated fruit. Among the treatments applied, only 1-methylcyclopropene inhibited ethylene production, hence supporting the involvement of this hormone in the development of scald. However, a common repression effect on the PPO gene combined with higher sorbitol content was found for both lovastatin and 1-methylcyclopropene-treated samples, suggesting also a non-ethylene-mediated process preventing the development of this disorder. The results presented in this work represent a step forward to better understand the physiological mechanisms governing the etiology of superficial scald in pears.

A comprehensive study on the main physiological and biochemical changes occurring during growth and on-tree ripening of two apple varieties with different postharvest behaviour.

Apple quality and the storage potential likely depend on a range of physiological and biochemical events occurring throughout fruit development and ripening. In this study, we investigated the major physiological (ethylene production and respiration) and biochemical changes (related to sugar and malic acid content as well as antioxidant metabolism) occurring during growth and on-tree ripening of two apple varieties ('Granny Smith' (GS) and 'Early Red One' (ERO)) with known differences in their postharvest behaviour, mainly firmness loss and susceptibility to superficial scald. Our results demonstrate that the higher storability and the limited loss of firmness of 'GS' fruit was associated to a higher acid content, mainly malic acid, that seemed to be regulated already at fruit set (20 DAFB). The reduced loss of firmness during storage in 'GS' was also associated to the fruit inability to produce ethylene upon harvest resulting from very low 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity. Sugar accumulation, on the other hand, was similar among both varieties as was also observed for the rate of fruit growth or the fruit respiration pattern. In addition, the higher susceptibility of 'GS' if compared to 'ERO' to superficial scald was not associated to peroxidative damage (malondialdehyde accumulation) nor to higher levels of the sesquiterpene α-farnesene but rather mediated by a fruit antioxidant imbalance resulting from higher H2O2 levels and lower antioxidant (peroxidase) enzymatic capacity. The interplay between ethylene, respiration and antioxidants or sugars and organic acids during apple growth and development is further discussed.

Evaluation of biocontrol capacity of Pseudomonas graminis CPA-7 against foodborne pathogens on fresh-cut pear and its effect on fruit volatile compounds.

The application of microorganisms to control the growth of foodborne pathogens is an alternative to the use of chemical additives. In this work, Pseudomonas graminis CPA-7 was tested as a biocontrol agent against Salmonella enterica and Listeria monocytogenes on fresh-cut pear under conditions that simulate its commercial application at 5 ±â€¯1 °C (under a modified atmosphere and antioxidant solution). The quality of the fresh-cut fruit, including the ethanol and acetaldehyde contents and the volatile profile, was determined. After the storage period, the L. monocytogenes population was reduced by 1-log unit by the presence of CPA-7; however, CPA-7 was not found to have antagonistic activity against S. enterica. The fruit quality (total soluble solids content and titratable acidity) was not negatively affected by CPA-7. The ethanol and acetaldehyde contents increased during the shelf-life of the fruit regardless of the presence of CPA-7. Some volatile compounds were key factors for discriminating samples from the two groups (the control group and the group that was inoculated with CPA-7). Some components are common in the volatile profile of pear (methyl acetate, 3-methylbutyl acetate, 1-butanol, 1-hexanol, and hexanal), and thus increases in their contents could enhance consumers flavour perception.

Biochemical and physiological changes during fruit development and ripening of two sweet cherry varieties with different levels of cracking tolerance.

The aim of this study was to investigate the biochemical and metabolic changes, related to oxidative stress, ethylene and respiration, cell wall modification and primary metabolism, between a high ('Prime Giant') and a low ('Cristalina') cracking susceptible sweet cherry cultivar during growth and ripening. While cherries are referred as a non-climacteric fruit, our results show that an increase of endogenous ethylene production at earlier fruit developmental stages is parallel to colour development and softening during growth. Higher cracking susceptibility was clearly associated to a higher fruit growth rate and accompanied by an increase net CO2 and ethylene production, on a cherry basis, leading to an enhanced accumulation of oxidative stress markers (i.e. H2O2 and MDA). As observed in other fruit species (i.e. tomatoes) higher cracking susceptibility was also related to enhanced activity of cell wall-modifying enzymes which in turn occurred in parallel to the ethylene rise. Overall, these results suggest that cracking development may be a more complex phenomenon than a mere consequence of altered fruit water absorption or turgor and point out the importance of ethylene on sweet cherry ripening and cracking development.

Cold-storage potential of four yellow-fleshed peach cultivars defined by their volatile compounds emissions, standard quality parameters, and consumer acceptance.

'Early Rich', 'Royal Glory', 'Sweet Dream(cov)', and 'Elegant Lady' peaches were stored at -0.5 °C for up to 40 days and then subjected to ripening at 20 °C for up to 3 days. Firmness, soluble solids content (SSC), titratable acidity (TA), color, consumer acceptance, and volatile compounds were then determined. The observed physicochemical changes included a significant decrease in firmness during both storage and commercialization periods. In contrast, the SSC, TA, and color remained constant during storage. Ten days of cold storage produced the highest total volatile emissions and the greatest consumer acceptance for 'Elegant Lady' and 'Sweet Dream(cov)', whereas similar results were obtained after 40 and 20 days for 'Royal Glory' and 'Early Rich', respectively. Volatile compounds that most consistently exhibited a positive correlation with consumer acceptance were dependent on the cultivar.

Comparison of the volatile profile and sensory analysis of 'Golden Reinders' apples after the application of a cold air period after ultralow oxygen (ULO) storage.

All efforts to improve fruit quality are rewarded when consumers are satisfied after tasting the fruit. Apples are often stored under controlled atmosphere conditions to preserve them over time, but this frequently results in a loss of flavor. The aim of this work, which was based on two seasons, was to evaluate the influence of a period of short-term air storage (periods of 2 and 4 weeks) after removal from ultralow oxygen (ULO) storage (1 kPa of O(2)/1 kPa of CO(2)) with respect to increases in volatile compound emissions and the effect on standard and sensory quality in 'Golden Reinders' apples. The results showed that emissions of 26 volatile compounds increased as a result of ULO + 2 weeks or ULO + 4 weeks of storage. However, the results of tastings involving a panel of consumers and trained experts revealed that this increase was not matched by corresponding increases in either the degree of consumer preference or flavor attributes.

Calcium dips enhance volatile emission of cold-stored 'Fuji Kiku-8' apples.

Despite the relevance of volatile production for overall quality of apple (Malus x domestica Borkh.) fruit, only a few studies have focused on the effects of calcium treatments on this quality attribute. In this work, 'Fuji Kiku-8' apples were harvested at commercial maturity, dipped in calcium chloride (2%, w/v), stored at 1 degrees C and 92% relative humidity for 4 or 7 months under either air or ultralow oxygen (ULO; 1 kPa of O(2)/2 kPa of CO(2)), and placed subsequently at 20 degrees C. Ethylene production, standard quality parameters, emission of volatile compounds, and the activities of some related enzymes were assessed 7 days thereafter. Calcium concentration was higher in CaCl(2)-treated than in untreated fruit, suggesting that the treatment was effective in introducing calcium into the tissues. Higher calcium contents were concomitant with higher flesh firmness and titratable acidity after storage. Furthermore, calcium treatment led to increased production of volatiles in middle-term stored apples, probably arising from enhanced supply of precursors for ester production as a consequence of increased pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities. After long-term storage, higher volatile emission might have arisen also from the enhancement of alcohol o-acyltransferase (AAT) activity, which was increased as a result of calcium treatment. In addition to storage period, the effects of calcium treatment were also partially dependent on storage atmosphere and more noticeable for fruit stored in air.

Lipoxygenase activity is involved in the regeneration of volatile ester-synthesizing capacity after ultra-low oxygen storage of 'Fuji' apple.

An extra period under cold air after ultra-low oxygen storage has been shown to increase the concentration of some volatile compounds emitted by stored 'Fuji' apples. The purpose of this work was to assess the role, if any, of lipoxygenase and hydroperoxide lyase activities in the regeneration of fruit capacity for volatile production after ultra-low oxygen storage. Fruits were stored at 1 °C and 92% relative humidity under ultra-low oxygen (1 kPa of O2/1 kPa of CO2); one lot was kept under hypoxia for 19 or 30 weeks, a second lot was maintained for 17 or 28 weeks under these conditions and then stored for 2 weeks in cold air, and a third lot remained for either 15 or 26 weeks under ultra-low oxygen followed by 4 weeks under cold air. Samples were placed subsequently at 20 °C, and analyses of volatile emission and enzyme activities were undertaken 1 and 7 days thereafter. Fruit stored during 4 weeks in cold air after ultra-low oxygen storage showed the highest capacity for volatile regeneration. Higher emission of volatiles by these samples was concomitant with higher levels of lipoxygenase activity. Results suggest that lipoxygenase activity, particularly in the flesh tissue, was strongly related to the regeneration of the emission of volatile compounds allowed by the extra period in cold air after ultra-low oxygen storage and, thus, appears to be a key control point for successful recovery of fruit ability for volatile compound production.

Long-term storage of Pink Lady apples modifies volatile-involved enzyme activities: consequences on production of volatile esters.

Pink Lady apples were harvested at commercial maturity and stored at 1 degrees C and 92% relative humidity under either air or controlled atmosphere conditions (2 kPa O 2:2 kPa CO 2 and 1 kPa O 2:1 kPa CO 2) for 27 weeks. Data on the emission of volatile compounds and on the activity of some related enzymes in both skin and flesh tissues were obtained during subsequent shelf life at 20 degrees C. Major effects of storage atmosphere and poststorage period were observed on the emission of volatile esters and their precursors. Changes in the production of volatile esters were partly due to alterations in the activity of alcohol o-acyltransferase, but the specific esters emitted by fruit after storage also resulted largely from modifications in the supply of the corresponding substrates. Samples stored under air were characterized by higher availability of acetaldehyde, whereas those stored under CA showed enhanced emission of the alcohol precursors ethanol and 1-hexanol (2 kPa O 2) and 1-butanol (1 kPa O 2), with accordingly higher production of ethyl, hexyl, and butyl esters. Multivariate analysis revealed that a large part of the observed differences in precursor availability arose from modifications in the activity of the enzymes considered. Higher pyruvate decarboxylase activity in air-stored fruit possibly accounted for higher acetaldehyde levels in these samples, while storage under 1 kPa O 2 led to significantly decreased lipoxygenase activity and thus to lessened production of 1-hexanol and hexyl esters. Low acetaldehyde availability together with enhanced hydroperoxide lyase and alcohol dehydrogenase levels in these fruits are suggested to have led to higher emission of 1-butanol and butyl esters.

Regeneration of volatile compounds in Fuji apples following ultra low oxygen atmosphere storage and its effect on sensory acceptability.

The aim of this work was to assess whether extra time spent under AIR conditions after storage in an ultra low oxygen (ULO) atmosphere could allow the regeneration of volatile compound emission without negatively affecting quality parameters and the consumer acceptability of Fuji apples. Fruits were stored for 19 and 30 weeks at 1 degrees C and 92% RH under ULO atmosphere conditions (1 kPa O 2:1 kPa CO 2) or under ULO conditions followed by different periods (2 and 4 weeks) in cold AIR atmosphere (ULO + 2w or ULO + 4w, respectively). Standard quality and emission of volatile compounds were analyzed after storage plus 1 and 7 days at 20 degrees C. Sensory attributes and acceptability were also determined after 7 days at 20 degrees C. The extra period of 30 weeks in an AIR atmosphere after ULO storage resulted in an increase in the concentration of the compounds that most contribute to the flavor of Fuji apples. These fruits were relatively well accepted by consumers despite a slight decline in firmness and acidity.

Volatile emission after controlled atmosphere storage of Mondial Gala apples (Malus domestica): relationship to some involved enzyme activities.

Mondial Gala apples were harvested at commercial maturity and stored at 1 degrees C under either air or controlled atmosphere (CA) conditions (2 kPa O2/2 kPa CO2 and 1 kPa O2/1 kPa CO2), where they remained for 3 or 6 months. Data on emission of selected volatile esters, alcohol precursors, and activity of some aroma-related enzymes in both peel and pulp tissues were obtained during subsequent shelf life of fruit and submitted to multivariate analysis procedures. CA storage caused a decrease in the emission of volatile esters in comparison to storage in air. Results suggest that lessened ester production was the consequence of modifications in activities of alcohol o-acyltransferase (AAT) and lipoxygenase (LOX) activities. For short-term storage, inhibition of lipoxygenase activity in CA stored fruit possibly led to a shortage of lipid-derived substrates, resulting in decreased production of volatile esters in spite of substantial ester-forming capacity that allowed for some recovery of fruit capacity for ester emission during the shelf life. For long-term storage, strong inhibition of AAT activity in CA stored fruit in combination with low LOX activities resulted in unrecoverable diminution of biosynthesis of volatile esters.

Characterization of Fuji apples from different harvest dates and storage conditions from measurements of volatiles by gas chromatography and electronic nose.

Volatile compounds in Fuji apples harvested at two different maturities were measured at harvest and after 5 and 7 months of cold storage (1 degrees C) in four different atmospheres. When the samples were characterized by both chromatographic measurements of volatiles and responses of an electronic nose, the analyses showed a clear separation between fruits from different storage conditions (a normal cold atmosphere and three controlled atmospheres). During poststorage, the apples were left to ripen for 1, 5, and 10 days at 20 degrees C before analytical measurements were done involving headspace-gas chromatography methods and electronic nose type quartz crystal microbalances. Electronic nose responses registered by seven different sensors were used to classify the apples using principal component analysis. It was possible to identify the samples from different storage periods, days of shelf life, and harvest dates, but it was not possible to differentiate the fruits corresponding to different cold storage atmospheres.