Interactive responses of gala apple fruit volatile production to controlled atmosphere storage and chemical inhibition of ethylene action

A comparison of the performance of conventional and eco-friendly extraction methods in the evaluation of total phenolics, antioxidant activity, and chemical composition of anise

In this work, the essential oil of Pimpinella anisum seeds was obtained by six different extraction methods. In the chemical composition analysis, 4, 6, 4, 1, 20, and 8 compounds were detected in the extracts obtained by Soxhlet, Ultrasonic-assisted (UAE), hydrodistillation using Clevenger apparatus (HDC), subcritical water extraction (SWE), supercritical carbon dioxide extraction (ScCO2) using three solvents (methanol (ScCO2-Met), ethanol (ScCO2-Et), and hexane (ScCO2-H)) and supercritical 1,1,1,2-tetrafluoroethane (ScR134a) methods, respectively. Also, the performances of the applied methods were compared by analysing the total phenolic content (TPC) and antioxidant activity of the extracts. Anethole was the main component of all extracts obtained by SWE (94.5%) and Soxhlet (94.5%) methods, respectively. Also, TPC values were the highest (508.5 mg GAE/100 g kb) in ScR134a extract and the lowest (27.77 mg GAE/100 g kb) in HDC extracts. The antioxidant capacity was found to be the highest in ScCO2-H (IC50 = 1.58 mg/mL) and the lowest in Soxhlet extracts (IC50 = 0.07 mg/mL). The results showed the great effectiveness of eco-friendly extraction SWE, ScCO2-Et, and ScR134a methods.

Effects of Different Irrigation Regimes, Nitrogen Levels and Storage Conditions on Volatiles of 'Gala' Apple

With a characteristic flavour and aroma, "Maçã de Alcobaça" are apples produced in the western region of the mainland of Portugal. Given the known influence of pre-harvest cultural techniques and post-harvest conservation methods on fruit quality, this work evaluated the effect of cultural factors and conservation methods on the volatile profile of 'Gala' apples. Tests were carried out during four seasons (2018 to 2021) in two 'Gala' apple orchards (F and S) maintained with different irrigation rates and nitrogen fertilisation [normal irrigation and normal nitrogen (Control, NINN), normal irrigation and excess nitrogen (NIEN), excess irrigation and normal nitrogen (EINN), excess irrigation and excess nitrogen (EIEN)], and under three storage conditions [Controlled Atmosphere + 1-methylcyclopropene (CA+1-MCP), Dynamic Controlled Atmosphere (DCA) and DCA+1-MCP]. The intact fruit volatiles were isolated by headspace solid-phase microextraction (HS-SPME) and analysed by Gas Chromatography with Flame Ionisation Detection and Gas Chromatography-Mass Spectrometry at harvest (T0) and after 8 months of storage (T8). HS-SPME volatiles from 'Gala' apples, obtained at T0 in control conditions, were characterised by trans,trans-α-farnesene dominance (36-69%), followed by hexyl acetate (5-23%) and hexyl hexanoate (3-9%). The four irrigation and nitrogen treatments did not evidence main changes in the apple volatile profile. Instead, storage conditions changed the ratio between compounds; previously undetected compounds attained high percentages and decreased the intensity of the dominant compounds in the control conditions. Although all storage conditions tested changed the volatile profile and emanation intensity, the effect was more accentuated in storage for 8 months with DCA+1-MCP.

Hypobaric treatment augments the efficacy of 1-MCP in apple fruit

This research aimed to extend the postharvest shelf life of Royal Gala apple during cold storage and maintain its market value in simulated retail conditions. Apples were treated with hypobaric pressure (50 kPa for 4 h) followed by 1-MCP (0.5 µL L-1, 0.7 µL L-1, and 1.0 µL L-1) treatment for 24 h individually and in combinations, stored at (1 ± 1 °C, 85 ± 3% RH) for 120 d and analyzed for different quality parameters (Peel color, firmness, weight loss, TSS, acidity, ethylene production rate, and respiration rate) at each 30 d interval, followed by a 20 d simulated retail condition at 20 ± 3 °C with 4 d interval. Results indicated that all 1-MCP concentrations were more effective in retaining quality compared to individual hypobaric treatment. However, a synergistic effect was observed by combining 1-MCP with hypobaric treatment. Among the combined treatments, 1.0 µL L-11-MCP + 50 kPa more effectively and significantly retained quality during cold storage. Furthermore, the apples were more juicy, tasty, and attractive in color than others in simulated conditions. Addition of hypobaric treatment to 1-MCP might reduce endogenous ethylene in fruit by outward diffusion and blocking further ethylene synthesis by the action of 1-MCP. However, in-depth study is required for further understanding the phenomena.

Timing of Ethylene Inhibition Affects Internal Browning and Quality of 'Gala' Apples in Long-Term Low Oxygen Storage

The objective of this study was to evaluate the timing of ethylene inhibition with preharvest and postharvest 1-methylcyclopropene (1-MCP) treatments on internal browning and quality of 'Gala' apples in long-term low O₂ storage. 'Gala' apples were obtained from the same commercial orchard during their harvesting period for 2 years of study. Preharvest 1-MCP orchard spray (3.8% a.i) was applied at the label rate of 60 g 1-MCP per acre in the first year. Postharvest 1-MCP (1 μl L^-1) treatments were made for 24 h at 0.5°C either at harvest time (1 day after harvest) or after storage in controlled atmosphere (CA) in both years. Apples were stored in 1.5 kPa O₂ + 0.5 kPa CO₂ or 0.6 kPa O₂ + <0.5 kPa CO₂ for 9 months in the first year and 1.5, 1.0, or 0.5 kPa O₂ + 0.5 kPa CO₂ for 8 months in the second year. Storage regimes with O₂ concentrations less than 1 kPa were based on fruit respiration using SafePod™ technology. After removal from storage, all apples were then evaluated for internal browning and other quality attributes after 1, 7, and 14 days at room temperature (RT, 21-22°C). Internal browning developed in 'Gala' apples during both years of study, with up to 16% incidence across treatments in the first year and up to 84% in the second year. Apples stored in 0.5-0.6 kPa O₂ had significantly less internal browning during both years of study, compared to apples stored in higher O₂. The effect of 1-MCP on internal browning was negligible in 0.5-0.6 kPa O₂ storage. 'Gala' stored in 1.5 kPa O₂ and treated with postharvest 1-MCP after storage had significantly less internal browning with preharvest 1-MCP than those without preharvest treatment. Apples treated with postharvest 1-MCP at harvest time, instead of after storage, did not exhibit this same effect. Preharvest 1-MCP-treated fruit maintained greater firmness retention than those without preharvest 1-MCP, and this effect was further enhanced when 1-MCP was applied after storage. Postharvest 1-MCP had no effect on firmness retention in fruit without preharvest 1-MCP, but lower O₂ maintained greater firmness in those apples. Preharvest 1-MCP had no significant effect on internal ethylene concentration, whereas it was reduced by postharvest 1-MCP at harvest time in the first year of study, regardless of storage regimes. However, internal ethylene was only affected by storage regime in the second year, with lower concentration in fruit from 0.5 kPa O₂ than in those from higher O₂. Greasiness developed only in the second year and postharvest 1-MCP consistently reduced it, regardless of treatment timing and storage regime. There was no greasiness in apples treated with postharvest 1-MCP at harvest and then held in 0.5 kPa O₂ for 8 months plus 14 days at room temperature. Soluble solids concentration and malic acid content were slightly higher in 'Gala' apples with preharvest 1-MCP compared to those without, whereas there was little and inconsistent effect of postharvest 1-MCP on these attributes. Overall, storage regimes with less than 1 kPa O₂ provided the least amount of internal browning and best quality attributes. Ethylene inhibition provided further benefits, but this was dependent on the timing of 1-MCP treatment.

Identification, Comparison and Classification of Volatile Compounds in Peels of 40 Apple Cultivars by HS-SPME with GC-MS

Aroma is an important quality indicator for apples and has a great influence on the overall flavour and consumer acceptance. However, the information of the aroma volatile compounds in apple peels is largely unknown. In this study, evaluation of volatile compounds in peels of 40 apple cultivars was carried out using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 78 volatile compounds were identified, including 47 esters, 12 aldehydes, 5 alcohols, 3 ketones, 1 acid and 10 others. Eight volatile compounds were common in all apple cultivars. Cultivar Changfu No. 2 contained the highest number of volatile compounds (47), while Qinyue contained the least (20). Honey Crisps had the highest volatile content, at 27,813.56 ± 2310.07 μg/kg FW, while Huashuo had the lowest volatile content, at 2041.27 ± 120.36 μg/kg FW. Principal component analysis (PCA) clustered the 40 apple cultivars into five groups. Aroma is cultivar-specific, volatile compounds of hexyl butyrate, hexyl 2-methylbutyrate and hexyl hexanoate, together with hexanal, (E)-2-hexenal, 1-hexanol, estragole and α-farnesene could be proposed for apple cultivar classification in the future.

Synergistic effects of ultrasound and β-d-glucosidase in aroma of orange juice

The synergistic effects of ultrasound and β-d-glucosidase in aroma of orange juice were investigated. β-d-Glucosidase significantly increased the content of ester, aldehyde, alcohol, terpene, acid, and phenol, and insignificantly increased the ketone content in orange juice. Enzyme-treated orange juice, compared with fresh untreated orange juice, was found to contain 15 novel aroma compounds, whereas three aroma compounds disappeared. Ultrasound improved the enzymatic action and the retention of more active flavors in juice than treatment with enzyme alone. However, simultaneous ultrasound and enzyme treatment decreased aroma quality. Therefore, the choice of the mode of ultrasound treatment is highly important. The present investigation will provide a reference for aroma-enhancing application of ultrasound combined with β-D-glucosidase. PRACTICAL APPLICATION: The study supplies a reference method for the aromatization of fruit juice.

Effect of 1-Methylcyclopropene (1-MCP) and Storage Atmosphere on the Volatile Aroma Composition of Cloudy and Clear Apple Juices

The effects of 1-methylcyclopropene (1-MCP), storage atmosphere (controlled (CA) or regular (RA)), and juice processing (clear or cloudy) on the volatile aroma compounds from McIntosh and Honeycrisp apples following 4-month storage were studied. All the major esters, aldehydes, and total volatile content from McIntosh juice were significantly affected by the two-way interaction between harvest maturity and 1-MCP treatment (p ≤ 0.01), as well as harvest maturity and storage atmosphere (p ≤ 0.001). In McIntosh juices, a remarkable reduction of all types of esters, aldehydes, most alcohols, and total volatile compounds was found when juices were prepared from 1-MCP-treated apples. In Honeycrisp, significant differences in the level of esters and the total volatile aroma was caused by storage atmosphere and juice processing techniques (p ≤ 0.001), but not by 1-MCP treatment. As compared to clear juices, cloudy juice samples from Honeycrisp had a considerably higher content of total volatiles, esters, and aldehydes.

Inside and Beyond Color: Comparative Overview of Functional Quality of Tomato and Watermelon Fruits

The quali-quantitative evaluation and the improvement of the levels of plant bioactive secondary metabolites are increasingly gaining consideration by growers, breeders and processors, particularly in those fruits and vegetables that, due to their supposed health promoting properties, are considered "functional." Worldwide, tomato and watermelon are among the main grown and consumed crops and represent important sources not only of dietary lycopene but also of other health beneficial bioactives. Tomato and watermelon synthesize and store lycopene as their major ripe fruit carotenoid responsible of their typical red color at full maturity. It is also the precursor of some characteristic aroma volatiles in both fruits playing, thus, an important visual and olfactory impact in consumer choice. While sharing the same main pigment, tomato and watermelon fruits show substantial biochemical and physiological differences during ripening. Tomato is climacteric while watermelon is non-climacteric; unripe tomato fruit is green, mainly contributed by chlorophylls and xanthophylls, while young watermelon fruit mesocarp is white and contains only traces of carotenoids. Various studies comparatively evaluated in vivo pigment development in ripening tomato and watermelon fruits. However, in most cases, other classes of compounds have not been considered. We believe this knowledge is fundamental for targeted breeding aimed at improving the functional quality of elite cultivars. Hence, in this paper, we critically review the recent understanding underlying the biosynthesis, accumulation and regulation of different bioactive compounds (carotenoids, phenolics, aroma volatiles, and vitamin C) during tomato and watermelon fruit ripening. We also highlight some concerns about possible harmful effects of excessive uptake of bioactive compound on human health. We found that a complex interweaving of anabolic, catabolic and recycling reactions, finely regulated at multiple levels and with temporal and spatial precision, ensures a certain homeostasis in the concentrations of carotenoids, phenolics, aroma volatiles and Vitamin C within the fruit tissues. Nevertheless, several exogenous factors including light and temperature conditions, pathogen attack, as well as pre- and post-harvest manipulations can drive their amounts far away from homeostasis. These adaptive responses allow crops to better cope with abiotic and biotic stresses but may severely affect the supposed functional quality of fruits.

Influence of 1-Methylcyclopropene Treatment on Postharvest Quality of Four Scab (Venturia inaequalis)-Resistant Apple Cultivars

Scab (Venturia inaequalis) is a very serious disease for apples causing up to 80% of loss in yield but there are only a few studies on postharvest quality of scab-resistant cultivars. In this study we evaluated the effect of 1-methylcyclopropene (1-MCP) on fruit quality, total phenolic content, and antioxidant capacity after storage of four scab-resistant cultivars and compared to a standard cultivar, “Golden Delicious.” In general, ethylene production and respiration rates significantly differed among cultivars, between control and 1-MCP-treated fruits, and between storage duration regimes. 1-MCP treatment retarded fruit softening and lowered juice pH but storage effect on soluble solids and acidity depended on cultivar and 1-MCP treatment. Total phenolic content was significantly affected by storage duration and 1-MCP treatment. Antioxidant capacity of the four scab-resistant cultivars was either similar to or significantly higher than that of “Golden Delicious” with the 1-MCP-treated fruits having significantly higher antioxidant capacity than the nontreated fruits after storage. Our results clearly show that the quality of four scab-resistant cultivars was comparable to that of “Golden Delicious” and 1-MCP effect differed among cultivars. These differences need to be considered in developing storage regime to minimize quality deterioration during long-term storage.

Biochemistry of Apple Aroma: A Review

Flavour is a key quality attribute of apples defined by volatile aroma compounds. Biosynthesis of aroma compounds involves metabolic pathways in which the main precursors are fatty and amino acids, and the main products are aldehydes, alcohols and esters. Some enzymes are crucial in the production of volatile compounds, such as lipoxygenase, alcohol dehydrogenase, and alcohol acyltransferase. Composition and concentration of volatiles in apples may be altered by pre- and postharvest factors that cause a decline in apple flavour. Addition of biosynthetic precursors of volatile compounds may be a strategy to promote aroma production in apples. The present manuscript compiles information regarding the biosynthesis of volatile aroma compounds, including metabolic pathways, enzymes and substrates involved, factors that may affect their production and also includes a wide number of studies focused on the addition of biosynthetic precursors in their production.

Metabolic profiling reveals ethylene mediated metabolic changes and a coordinated adaptive mechanism of 'Jonagold' apple to low oxygen stress

Apples are predominantly stored in controlled atmosphere (CA) storage to delay ripening and prolong their storage life. Profiling the dynamics of metabolic changes during ripening and CA storage is vital for understanding the governing molecular mechanism. In this study, the dynamics of the primary metabolism of 'Jonagold' apples during ripening in regular air (RA) storage and initiation of CA storage was profiled. 1-Methylcyclopropene (1-MCP) was exploited to block ethylene receptors and to get insight into ethylene mediated metabolic changes during ripening of the fruit and in response to hypoxic stress. Metabolic changes were quantified in glycolysis, the tricarboxylic acid (TCA) cycle, the Yang cycle and synthesis of the main amino acids branching from these metabolic pathways. Partial least square discriminant analysis of the metabolic profiles of 1-MCP treated and control apples revealed a metabolic divergence in ethylene, organic acid, sugar and amino acid metabolism. During RA storage at 18°C, most amino acids were higher in 1-MCP treated apples, whereas 1-aminocyclopropane-1-carboxylic acid (ACC) was higher in the control apples. The initial response of the fruit to CA initiation was accompanied by an increase of alanine, succinate and glutamate, but a decline in aspartate. Furthermore, alanine and succinate accumulated to higher levels in control apples than 1-MCP treated apples. The observed metabolic changes in these interlinked metabolites may indicate a coordinated adaptive strategy to maximize energy production.

Organic food processing: a framework for concept, starting definitions and evaluation

In 2007 EU Regulation (EC) 834/2007 introduced principles and criteria for organic food processing. These regulations have been analysed and discussed in several scientific publications and research project reports. Recently, organic food quality was described by principles, aspects and criteria. These principles from organic agriculture were verified and adapted for organic food processing. Different levels for evaluation were suggested. In another document, underlying paradigms and consumer perception of organic food were reviewed against functional food, resulting in identifying integral product identity as the underlying paradigm and a holistic quality view connected to naturalness as consumers' perception of organic food quality. In a European study, the quality concept was applied to the organic food chain, resulting in a problem, namely that clear principles and related criteria were missing to evaluate processing methods. Therefore the goal of this paper is to describe and discuss the topic of organic food processing to make it operational. A conceptual background for organic food processing is given by verifying the underlying paradigms and principles of organic farming and organic food as well as on organic processing. The proposed definition connects organic processing to related systems such as minimal, sustainable and careful, gentle processing, and describes clear principles and related criteria. Based on food examples, such as milk with different heat treatments, the concept and definitions were verified. Organic processing can be defined by clear paradigms and principles and evaluated according criteria from a multidimensional approach. Further work has to be done on developing indicators and parameters for assessment of organic food quality.

Advances in fruit aroma volatile research

Fruits produce a range of volatile compounds that make up their characteristic aromas and contribute to their flavor. Fruit volatile compounds are mainly comprised of esters, alcohols, aldehydes, ketones, lactones, terpenoids and apocarotenoids. Many factors affect volatile composition, including the genetic makeup, degree of maturity, environmental conditions, postharvest handling and storage. There are several pathways involved in volatile biosynthesis starting from lipids, amino acids, terpenoids and carotenoids. Once the basic skeletons are produced via these pathways, the diversity of volatiles is achieved via additional modification reactions such as acylation, methylation, oxidation/reduction and cyclic ring closure. In this paper, we review the composition of fruit aroma, the characteristic aroma compounds of several representative fruits, the factors affecting aroma volatile, and the biosynthetic pathways of volatile aroma compounds. We anticipate that this review would provide some critical information for profound research on fruit aroma components and their manipulation during development and storage.

Functional diversity among sensory receptors in a Drosophila olfactory circuit

The ability of an animal to detect, discriminate, and respond to odors depends on the function of its olfactory receptor neurons (ORNs), which in turn depends ultimately on odorant receptors. To understand the diverse mechanisms used by an animal in olfactory coding and computation, it is essential to understand the functional diversity of its odor receptors. The larval olfactory system of Drosophila melanogaster contains 21 ORNs and a comparable number of odorant receptors whose properties have been examined in only a limited way. We systematically screened them with a panel of ∼500 odorants, yielding >10,000 receptor-odorant combinations. We identify for each of 19 receptors an odorant that excites it strongly. The responses elicited by each of these odorants are analyzed in detail. The odorants elicited little cross-activation of other receptors at the test concentration; thus, low concentrations of many of these odorants in nature may be signaled by a single ORN. The receptors differed dramatically in sensitivity to their cognate odorants. The responses showed diverse temporal dynamics, with some odorants eliciting supersustained responses. An intriguing question in the field concerns the roles of different ORNs and receptors in driving behavior. We found that the cognate odorants elicited behavioral responses that varied across a broad range. Some odorants elicited strong physiological responses but weak behavioral responses or weak physiological responses but strong behavioral responses.

'Diffuse skin browning' in 1-MCP-treated apples: etiology and systems of control

BACKGROUND

'Diffuse skin browning' (DSB) is a physiological disorder that affects Golden Delicious apples treated with 1-methylcyclopropene (1-MCP). Although a very high incidence is found, very little is known about the etiology of this disorder. This study aims to provide an understanding of the causes of this disorder and prevent it.

RESULTS

A very high incidence of DSB was found in 1-MCP-treated apples independent of the location of the orchard. Similar to superficial scald, harvest maturity determines the DSB incidence, with the more mature fruit being less sensitive. The 1-MCP dose (156 nL L(-1) or 625 nL L(-1)) and the temperature at which the 1-MCP treatment was applied (0.5 or 20 °C) did not affect the incidence of DSB. Diphenylamine (DPA) treatment did not prevent DSB, contrary to superficial scald. Additionally, controlled atmosphere storage only partially reduced the incidence of DSB, whereas progressive cooling strategies completely inhibited DSB occurrence. A direct correlation was found between the sensitivity of the Golden Delicious clone to russeting and its sensitivity to develop DSB during storage.

CONCLUSION

Our results indicated that DSB and superficial scald are two different disorders involving different oxidative processes. DSB can be prevented by progressive cooling and selection of russeting-resistant clones.

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.

Impact of innovative controlled atmosphere storage technologies and postharvest treatments on volatile compound production in cv. Pinova apples

Organically grown apples cv. Pinova harvested at two different dates were stored at 1.3 degrees C for up to 4 months in air, up to 7 months in ULO (1.5 kPa of O(2) and 1.3 kPa of CO(2)) and in dynamic controlled atmosphere (DCA) conditions (0.4-0.6 kPa of O(2) and 0.6-0.8 kPa of CO(2)); the DCA storage method involved the use of a chlorophyll fluorescence monitoring system in order to detect low-O(2) stress in apples and to allow for the dynamic adaptation of storage atmosphere to O(2) levels that were lower than in ULO but still tolerated by fruits. A postharvest 1-MCP treatment (for 24 h at 1.3 degrees C) and a hot water treatment (for 180 s at 50 degrees C) were also tested on apples stored afterward in ULO and air, respectively. Volatile compounds isolated from the pulp of fruits were measured after 4 and 7 months, just upon removal from storage and after 11 days at 22 degrees C. Total amount of aroma compounds detected in apples stored in DCA was markedly higher (from 2- to 4-fold) than in fruits exposed to 1-MCP + ULO but, at most sampling times, significantly lower than in ULO fruits. Moderate differences in storage atmosphere composition between ULO and DCA significantly affected both total amount and profile of volatile esters. Analogous effects were observed on the alcohol precursors of the main esters. Exposure to 1-MCP inhibited biosynthesis of straight-chain esters more than that of branched-chain esters. The hot water treatment did not seem to produce marked changes in volatile composition after four months of air storage, except for a sharp accumulation of aldehydes during the shelf-life time. DCA storage technology, besides avoiding any chemical treatment, can preserve apple aroma compounds better than 1-MCP + ULO during long-term storage.

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.

Quality and Volatile Emission Changes of `Mondial Gala' Apples during On-tree Maturation and Postharvest Storage in Air or Controlled Atmosphere

Starch index (SI), color, firmness, titratable acidity (TA), soluble solids content (SSC), ethylene production, and aroma volatile emission were recorded weekly during on-tree maturation of `Mondial Gala' apples. Fruit were harvested on commercial date and held for 3.5 and 6.5 months in regular atmosphere (RA) or in three controlled atmospheres (CA) (2% O2 :2% CO2, 1% O2 : 1 % CO2 and 1% O2 :3% CO2). After each storage period plus 0 and 7 days at 20 °C, color, firmness, TA, SSC, aroma volatile emission, acetaldehyde and ethanol concentrations, and sensory acceptability were evaluated. At orchard, changes in SI, SSC, background color, and aroma volatile emission were almost concomitant or slightly previous to the increase in ethylene production. During storage, all three CA conditions, regardless of storage period, led to better preservation of standard quality. CA-stored fruit also received higher acceptability scores, although aroma volatile emission was decreased in response to these storage conditions. At the end of long storage (plus shelf life period), fruit stored in 1 :1 atmosphere showed a good retention of firmness and TA in comparison to the rest of CA-fruit. Fruit stored under all considered CA conditions showed similar aroma volatile emission after 3.5 or 6.5 months of storage. Storage period had no apparent influence on the aroma volatile emission of CA-stored apples, with the exception of fruit stored in 2:2 atmosphere immediately upon removal from storage. No significant differences in sensory acceptability were found either for fruit stored under different CA conditions during 3.5 months immediately after transfer to 20 °C. In contrast, fruit stored in either 1 : 1 or 2: 2 atmospheres during 6.5 months were better accepted by consumers than those stored in 1 : 3 atmosphere upon removal from cold storage. However, these differences disappeared after 7 days of shelf-life at 20 °C.

Salicylic acid, ethephon, and methyl jasmonate enhance ester regeneration in 1-MCP-treated apple fruit after long-term cold storage

Volatile esters, primarily synthesized in peel tissues, are major aromatic components of apple fruits [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. The use of cold storage combined with 1-methylcyclopropene (1-MCP) treatment prolongs the life of apples but represses the regeneration of esters during poststorage ripening. In this study, the regeneration of total esters was significantly increased in apple fruits treated with salicylic acid (SA) and Ethephon (ETH) that had been treated once or twice with 1-MCP. However, methyl jasmonate (MeJA) treatment resulted in regeneration of total esters after a single 1-MCP treatment. To determine the mechanism by which SA, ETH, and MeJA regulate ester regeneration, the apple alcohol acyltransferase gene (MdAAT2) was investigated at the mRNA, protein, and enzyme activity levels. Genes associated with ethylene perception were also investigated by RT-PCR. The results suggest that MdAAT2 controls ester regeneration and that MdETR1 plays a key role in ethylene perception and regulation of downstream MdAAT2 gene expression during poststorage. Ester compounds and concentrations differed in peels treated with different signal molecules, indicating that regulation of the pathway upstream of straight-chain ester biosynthesis depended on the regulation of lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity by SA, ETH, and MeJA during poststorage ripening.

The use of 1-methylcyclopropene (1-MCP) on fruits and vegetables

The recent availability of the inhibitor of ethylene perception, 1-methylcyclopropene (1-MCP), has resulted in an explosion of research on its effects on fruits and vegetables, both as a tool to further investigate the role of ethylene in ripening and senescence, and as a commercial technology to improve maintenance of product quality. The commercialization of 1-MCP was followed by rapid adoption by many apple industries around the world, and strengths and weaknesses of the new technology have been identified. However, use of 1-MCP remains limited for other products, and therefore it is still necessary to speculate on its commercial potential for most fruits and vegetables. In this review, the effects of 1-MCP on fruits and vegetables are considered from two aspects. First, a selected number of fruit (apple, avocado, banana, pear, peaches and nectarines, plums and tomato) are used to illustrate the range of responses to 1-MCP, and indicate possible benefits and limitations for commercialization of 1-MCP-based technology. Second, an outline of general physiological and biochemical responses of fruits and vegetables to the chemical is provided to illustrate the potential for use of 1-MCP to better understand the role of ethylene in ripening and senescence processes.