Changes in the odor-active volatile compounds produced by `Gala' apples [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Gala'] were measured after 4, 10, and 20 weeks storage at 1 °C in regular atmosphere (RA) or controlled atmosphere (CA), and 16 weeks in CA followed by 4 weeks in RA. Aroma was evaluated using the gas chromatography-olfactometry method Osme. Production of volatile esters decreased along with corresponding fruity aromas during CA storage. Hexyl acetate, butyl acetate, and 2-methylbutyl acetate were emitted in the largest amounts and perceived with the strongest intensities from RA-stored fruit. While hexyl acetate and butyl acetate concentrations and aroma intensities decreased during CA storage, 2-methylbutyl acetate remained at the RA concentration until apples had been stored 16 weeks in CA. Perception intensities of methylbutyrate esters with apple or berrylike odors decreased less than straight chain esters in CA-stored fruit. 4-Allylanisole, ß-damascenone, and 1-octen-3-ol, as well as an unknown compound with a watermelon descriptor, were perceived more in RA-stored fruit than in CA-stored apples. Factor analysis indicated the importance of these compounds in `Gala' apples stored 4 weeks in RA. Even though these compounds do not have an apple odor, they contribute to fresh `Gala' aroma.
Anne Plotto, Mina R. McDaniel, and James P. Mattheis
Xuetong Fan, James P. Mattheis, and John K. Fellman
The effect of exogenous methyl jasmonate (MJ) and jasmonic acid (JA) compared with the effect of ethephon on surface color and quality of `Golden Delicious' and `Fuji' apples (Malus ×domestica Borkh.) was studied. Treatments were applied by dipping fruit in water solutions of JA, MJ, or ethephon or by exposing fruit to MJ vapors. Response to MJ vapor treatment depended on fruit developmental stage, with the maximum effect occurring as fruit began to produce ethylene. MJ promoted color changes more effectively than JA. The promotive effect of JA increased with JA concentration. A minimum concentration of 0.1 mmol·L-1 JA was needed to promote significant color change within 15 d at 20 °C. JA at 1 or 10 mmol·L-1 promoted color change more effectively than 0.35 or 3.5 mmol·L-1 ethephon. The magnitude of JA-promoted responses decreased at lower temperatures. Treatments with 10 mmol·L-1 JA or 3.5 mmol·L-1 ethephon were phytotoxic. Treatments using JA at 1 or 10 mmol·L-1 in water promoted loss of fruit titratable acidity compared to controls. Firmness and soluble solids content were relatively unresponsive to JA treatments. Based on these results, using JA and MJ to promote degreening of apple fruit with minimal loss of other quality attributes appears feasible.
Jinwook Lee, James P. Mattheis, and David R. Rudell
‘Royal Gala’ apples can be susceptible to the incidence of fruit cracking and senescent flesh breakdown during cold storage. Because the development of these physiological disorders in other cultivars can be influenced by humidity during storage, the objective of this study was to evaluate the effect of high storage humidity on fruit quality attributes and incidence of physiological disorders in cold-stored ‘Royal Gala’ apples. Fruit obtained from a commercial orchard were kept in cardboard boxes with or without a perforated polyethylene liner during and after cold storage. High storage humidity induced by the perforated polyethylene liner reduced fresh weight loss but enhanced the change of fruit circumference after cold storage. High storage humidity contributed the most reduction of cortex lightness (L*) and hue angle (h o) in stem-end cortex tissues during shelf life. Fruit stored with liners had reduced internal ethylene concentration (IEC) and outer cortex firmness after removal from storage compared with control fruit. Furthermore, high storage humidity prevented shriveling but provoked fruit cracking. The incidence and severity of flesh breakdown were further aggravated during shelf life, compared with cold storage, regardless of a liner application. Overall, maintaining high storage humidity by applying a perforated polyethylene liner can contribute to delaying fresh weight loss, reducing IEC, and preventing fruit shriveling but can enhance cortex tissue browning, loss of flesh firmness, and incidence of fruit cracking during cold storage and shelf life.
Ruixiang Yan, Joshua B. Gurtler, James P. Mattheis, and Xuetong Fan
The objective of the study was to evaluate the effect of trichome (fuzz) removal on the efficacy of ultraviolet-C in inactivating Escherichia coli O157:H7 on peach fruit, and quality of peach [Prunus persica (L.) Batsch, cv. PF25] fruit as affected by fuzz removal and ultraviolet-C. Peach (cultivar PF25) fruit, with and without fuzz removal, were inoculated with a five-strain cocktail of E. coli O157:H7 and treated with ultraviolet-C at doses of 0, 221, and 442 mJ/cm2. Fuzz was rubbed off using damped cloths. Survival of E. coli populations was determined at days 1, 4, and 7 at 20 °C. To study fruit quality, noninoculated fruit with and without fuzz removal were treated with ultraviolet-C at the same doses. Results demonstrated that ultraviolet-C at 442 mJ/cm2 reduced the population of E. coli by 1.2 to 1.4 log colony-forming units (CFU)/fruit on peach with fuzz, and 0.9 to 1.1 log CFU/fruit on fruit without fuzz 1 day after ultraviolet-C treatment. However, E. coli populations of all samples were similar with additional storage time, resulting in no significant difference among the treatments after 7 days of storage at 20 °C. Ultraviolet-C at doses up to 442 mJ/cm2 did not have any significant effect on the surface color of peaches during 7 days of storage, although fruit with fuzz removal increased L*, hue, and chroma values. In addition, fuzz removal promoted the loss of firmness during storage. Furthermore, ultraviolet-C at 442 mJ/cm2 increased antioxidant capacity of peach skin with fuzz. Overall, our results suggested that fuzz removal had marginal effects on the efficacy of ultraviolet-C, and ultraviolet-C did not negatively affect the quality of peaches.
P. Lawrence Pusey, David R. Rudell, Eric A. Curry, and James P. Mattheis
The stigmatic secretions of pomaceous flowers serve as a natural medium not only for pollen, but also for the pathogen Erwinia amylovora (Burr.) Winslow et al. and other microorganisms. To understand the microecology on the stigma, exudates from cultivars of pear (Pyrus communis L.), apple (Malus pumila P. Mill.), and crab apple [Malus mandshurica (Maxim.) Kom.] were analyzed for free sugars and free amino acids as available carbon and nitrogen sources. Extracts were obtained at different stages of anthesis by submerging and sonicating stigmas in water. Certain free sugars (glucose and fructose) and free amino acids (proline, asparagine, glutamic acid, and glutamine) were consistently predominant and increased during anthesis. Apple stigma extracts were also analyzed for polysaccharides and proteins. Of major components identified for apple, free sugars made up 4.5% by mass; polysaccharides (composed of arabinose and galactose), 49.6%; and proteins, 45.9%. The two largest components are likely present as glycoproteins. This may be the first report on characteristics of rosaceous stigma exudates that includes the identity of specific free sugars, free amino acids, and polysaccharide subcomponents. Discussion includes the comparison of pomaceous stigma exudates to those of other plants and the microecological implications.
J. K. Fellman, D. S. Mattinson, James P. Mattheis, and D.A. Buchanan
Volatile esters from acids and alcohols are important components of flavor and odor perception in apples (Malus domestica Borkh.). We are interested in understanding the biochemical basis for ester synthesis/flavor retention in `Gala' apples held in controlled atmosphere storage. The relationship between acetyl CoA alcohol transferase (AAT) acetate ester-formin activity, non-ethylene volatile emission, and flesh volatile content of `Gala' apples during the maturation period and after removal from CA storage was investigated. At the appropriate times, apples were sampled for volatile compounds in the headspace and flesh using solid sorbent along with purge-and-trap capillary gas chromatography. Subsequently, acetate ester forming activity was assayed on partially-purified extracts of cortical tissue. During storage, the accumulation of the major flavor notes butyl acetate and 2-methyl butyl acetate in the flesh was decreased as oxygen levels in storage atmospheres were lowered. AAT activity is closely linked to the onset of climacteric ripening and is sensitive to atmospheres having low oxygen contents.
David R. Rudell, Sara Serra, Nathanael Sullivan, James P. Mattheis, and Stefano Musacchi
Physiological variability within a large canopy ‘d’Anjou’ tree results from agronomic and environmental factors. Fruit diversity within the canopy was surveyed using metabolic profiling to identify metabolism associated variability within the canopy. Different portions of the same fruit were evaluated to determine future precise sampling protocols for metabolic profiling of pear. We expected that the metabolic profile of the peel and cortex would be diverse and these differences would highlight specific metabolic pathways as influenced by these conditions. Another focus of this work was developing an untargeted metabolic profiling protocol tailored for pear using a combination of extractions coupled with GC-MS and LC-MS analysis. ‘d’Anjou’ pear fruit harvested from two different zones of trees trained to an open vase canopy were maintained at room temperature for 24 days to observe any changes in external phenotype and metabolic profile. Fruit harvested from the internal canopy were greener as also indicated by high Index of Absorbance Difference (IAD) and hue angle values. Metabolic profile differences between tree positions were widespread and included metabolites from many pathways beyond those associated with peel color. In addition, peel metabolic profile was different depending upon the tissue position (top vs. bottom) sampled from the pears. Specific pathways altered by tree position included those potentially linked to fruit quality and ripeness, including malic acid and aroma volatile (V) levels, as well as light environment, such as flavonol glycoside levels. Present results warrant further future work targeting these changes over time during storage and alongside fruit quality analyses to validate the impacts on ripening and tree factors. In addition, outcomes indicate tissue sampling strategies require consistency with respect to the region of the pear fruit sampled for metabolomics.
Rachel S. Leisso, Ines Hanrahan, James P. Mattheis, and David R. Rudell
The physiology and metabolism characterizing postharvest chilling and CO2 injury in apple has important implications for postharvest management of soft scald and soggy breakdown. This research assessed differences of primary metabolism related to soggy breakdown (cortex CI) and CO2 cortex injury in ‘Honeycrisp’ apple fruit. Results indicate that prestorage temperature conditioning, diphenylamine (DPA), and CA treatments alter fruit metabolism and affect peel and cortex storage disorder outcome. A preliminary summary of primary metabolism involved with soggy breakdown under high CO2 includes increased activity in glycolysis/gluconeogenesis, propionate metabolism, and alanine, aspartate, and glutamate metabolism.
Anne Plotto, Anita N. Azarenko, Mina R. McDaniel, Patrick W. Crockett, and James P. Mattheis
Eating quality of `Gala' and `Fuji' apples (Malus domestica Borkh.) from multiple harvests and storage durations was assessed using an untrained consumer panel. Apples were harvested at weekly intervals for 6 weeks and stored in air. Changes due to harvest maturity and storage for overall liking (OL), sweetness, tartness, firmness, and flavor intensity were evaluated over 8 months. A multivariate factor analysis revealed multicollinearity for OL, sweetness, and flavor intensity ratings in both cultivars. These attributes had the highest loadings in the first factor, explaining 51% and 52% of the variance of `Gala' and `Fuji' data sets, respectively, and were interpreted as a quality factor. Tartness and firmness had the highest loadings in the second factor for `Gala', explaining an additional 23% of the variability and reducing that cultivar's data set to two factors. For `Fuji', however, tartness and firmness were independent and included in factors 2 and 3, respectively. Factors 2 and 3 were interpreted as maturity factors, which explained 23% and 12% of the variance. The plots of the mean factor scores provided a multivariate technique to illustrate that panelists could differentiate between the stages of maturity of apples. Canonical correlations were calculated between the sensory and instrumental data. Only firmness measurements were correlated with sensory ratings for firmness (r = 0.53 and 0.44 for `Gala' and `Fuji', respectively).
Jinhe Bai, Elizabeth A. Baldwin, Kevin L. Goodner, James P. Mattheis, and Jeffrey K. Brecht
Apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf. (`Gala', `Delicious', `Granny Smith' and `Fuji')], pretreated or nontreated with 1-methylcyclopropene (1-MCP, 0.6 to 1.0 μL·L–1 for 18 hours at 20 °C), were stored in controlled atmosphere (CA, 1 to 1.5 kPa O2; 1 to 2 kPa CO2) or in regular atmosphere (RA) for up to 8 months at 1 °C. Firmness, titratable acidity (TA), soluble solids content (SSC), and volatile abundance were analyzed every month directly or after transfer to air at 20 °C for 1 week to determine effect of 1-MCP, storage atmosphere and storage time on apple quality immediately after cold storage and after simulated marketing conditions at 20 °C. The 1-MCP ± CA treatments delayed ripening and prolonged storage life as indicated by delayed loss of firmness and TA in all four cultivars during storage. The 1-MCP ± CA also slightly delayed loss of SSC for `Gala' but had no effect on SSC levels for the other cultivars. There were differences among treatments for firmness and TA content [(1-MCP + RA) > CA] for `Gala', `Delicious', and `Granny Smith' apples, but not for `Fuji'. These differences were generally exacerbated after transfer of fruit to 20 °C for 1 week. A combination of 1-MCP + CA was generally best [(1-MCP + CA) > (1-MCP + RA) or CA] for maintaining `Delicious' firmness and TA. However, the treatments that were most effective at retaining TA and firmness also retained the least volatiles. The results indicate that the efficacy of 1-MCP and CA in maintaining apple quality factors is cultivar dependent and that 1-MCP + RA may be a viable alternative to CA for optimal eating quality for some cultivars.