计量经济分析 = Econometric analysis

Jasmonates: biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany

Nondestructive measurement of fruit and vegetable quality by means of NIR spectroscopy: A review

Much of natural product chemistry concerns a group of compounds known as secondary metabolites. These low-molecular-weight metabolites often have potent physiological activities. Digitalis, morphine and quinine are plant secondary metabolites, whereas penicillin, cephalosporin, ergotrate and the statins are equally well known fungal secondary metabolites. Although chemically diverse, all secondary metabolites are produced by a few common biosynthetic pathways, often in conjunction with morphological development. Recent advances in molecular biology, bioinformatics and comparative genomics have revealed that the genes encoding specific fungal secondary metabolites are clustered and often located near telomeres. In this review, we address some important questions, including which evolutionary pressures led to gene clustering, why closely related species produce different profiles of secondary metabolites, and whether fungal genomics will accelerate the discovery of new pharmacologically active natural products.

Fungal secondary metabolism — from biochemistry to genomics

1-Methylcyclopropene: a review

Effect of O2 and CO2 partial pressure on selected phenomena affecting fruit and vegetable quality.

Highbush blueberry (Vaccinium corymbosum L. 'Bluecrop') fruit sealed in low-density polyethylene pack- ages were incubated at 0, 5, 10, 15, 20, or 25C until O 2 and CO2 levels in the package reached a steady state. A range of steady-state O2 partial pressures (1 to 18 kPa) was created by placing a range of fruit weights within packages having a constant surface area and film thickness. The steady-state O 2 partial pressure in packages containing the same weight of fruit decreased as temperature increased, indicating the respiratory rate rose more rapidly (i.e., had a greater sensitivity to temperature) than O 2 transmission through the film. Steady-state O 2 and CO2 partial pressures were used to calculate rates of O 2 uptake. CO2 Production. and the respiratory quotient (RO). The effects of tem- perature and 02 partial pressure on O 2 uptake and CO2 production and the RQ were characte~zed. The steady-state O, partial pressure at which the fruit began to exhibit anaerobic CO 2 production (the RQ breakpoint) increased with increasing temperature, which implies that blueberry fruit can be stored at lower O 2 partial pressures when stored at lower temperatures. Studies using controlled-atmosphere (CA) storage techniques have indicated that shelf-life extension can be obtained for blue- berry (Vaccinium spp.) fruit using combinations of elevated CO 2 and reduced O 2 in the storage environment (Ceponis and Cap- pellini, 1985; Smittle and Miller, 1988). CA storage of high- bush blueberry fruit is now a commercial reality and current conditions range from 1.5 to 2.5 kpa O 2 (1% O2 = 1.013 kPa O 2 at 1 atm) and 5 to 12 kPa CO2 at 0C. Present-day commercial techniques for packaging blueberry fruit do not modify O 2 and CO 2 to levels that would enhance storage. Modified-atmosphere packaging (MAP) has the poten- tial to provide low O 2/high CO2 regimes similar to those of CA storage, but throughout the marketing chain. Ideally, a package should maintain the appropriate atmospheric composition over the range of temperatures commonly encountered between har- vest and consumption. Poor temperature control, however, can cause package O 2 levels to drop low enough to induce anaerobic

/pdf/modified-atmosphere-packaging-of-blueberry-fruit-effect-of-2ljl2djucg.pdf

Modified-atmosphere Packaging of Blueberry Fruit: Effect of Temperature on Package O2 and CO2

Fruit of 'Redchief Delicious' apple ( Malus sylvestris (L) Mill. var. domestica (Borkh.) Mansf.) were harvested 1 week before the climacteric (harvest 1), at the onset of the climacteric (harvest 2), and 1 week after the onset of the climacteric (harvest 3). Fruit were stored at 0, 5, 10, 15, or 20 °C and were treated with 0.7 µL·L -1 1-MCP on a once-per- week, once-per-2-week, once-per-month, and once-per-year basis or were left nontreated. The initial 1-MCP treatment was at 20 °C and subsequent applications were at storage temperatures. The compound slowed softening at all temperatures relative to nontreated fruit, however as temperature decreased, the benefits of 1-MCP application became less pronounced. Effectiveness of 1-MCP declined slightly as harvest maturity increased. Efficacy of 1-MCP treatment increased with greater frequency of application at 5, 10, 15, and 20 °C, but not at 0 °C. Fruit stored without refrigeration (20 °C) for more than 100 days did not soften significantly when treated once per week with 1-MCP. However, decay was a significant problem for treated and nontreated fruit stored at temperatures >5 °C; 1-MCP application reduced, but did not prevent decay. Rate of decline in titratable acidity increased with storage temperature and 1-MCP had no significant effect on retarding the decline in acid content. Minimal (Fo) and maximal (Fm) chlorophyll fluorescence was altered markedly by 1-MCP application, but the ratio of (Fm-Fo)/Fm was only slightly affected. The most effective 1-MCP treatment frequency was once per week and, at all elevated temperatures (5, 10, 15, and 20 °C), slowed loss of firmness to a greater extent than refrigeration (0 °C) alone. Application of 1-MCP resulted in greater retention of firmness than controlled atmosphere (CA) with O2 and CO2 at 1.5 kPa and 3 kPa, respectively. Data suggest that 1-MCP application, has the potential to reduce reliance on refrigeration and CA storage for maintaining firmness of 'Redchief Delicious' apple, especially for relatively short storage durations (<50 days) when fruit are harvested within a week of the ethylene

/pdf/harvest-maturity-storage-temperature-and-1-mcp-application-1nqf88dkb2.pdf

Harvest maturity, storage temperature, and 1-MCP application frequency alter firmness retention and chlorophyll fluorescence of 'Redchief Delicious' apples

ADDITIONAL INDEX WORDS. respiration, ripening, fermentation, glycolysis, ethanol, fruit, veg- etables, safe working atmosphere SUMMARY. The application of low oxygen through modified atmosphere packaging (MAP) is a technique used successfully to preserve the visual quality of lettuce and some other commodi- ties. The expansion of use of low O 2 via MAP to preserve quality of most commodities is limited by technical difficulties achieving target O 2 concentrations, adverse physiological responses to low O 2 , and lack of beneficial responses to low O 2 . Low O 2 often is not used simply because the physiological responses governed by the gas are not limiting quality maintenance. For instance, shelf life may be governed by decay susceptibility, which is largely unaffected by low O 2 and may actually be exacerbated by the conditions encountered in hermetically sealed packages. Physiological processes influenced by low O 2 and limit storability are discussed. The interdependence of O 2 concentration, O 2 uptake by the product, and temperature are discussed relative to requirements for packaging films.

/pdf/responses-of-horticultural-commodities-to-low-oxygen-limits-1uxugt909s.pdf

Responses of horticultural commodities to low oxygen: limits to the expanded use of modified atmosphere packaging.

The objective of this research was to study the potential of near-infrared (NIR) diffuse reflectance between 800 nm and 1700 nm for determining the firmness and sugar content of apples and to ascertain the effects of apple peel and variety on the NIR prediction of these two quality attributes. The spectral reflectance data were acquired from both peeled and unpeeled ‘Empire', ‘Golden Delicious', and ‘Red Delicious’ apples. Statistical models were developed using principal component analysis/regression. Lower correlations of prediction were obtained (r=0.38 to 0.58) between NIR measurement and Magness-Taylor firmness for both unpeeled and peeled fruit, with the standard errors of prediction (SEP) between 6.6 N and 10.1 N. Improved predictions were obtained when NIR reflectance was correlated with the slope of the Magness-Taylor force-deformation curves. Excellent predictions of the sugar content in peeled apples were obtained (r=0.93 to 0.97; SEP=0.37 to 0.42 °Brix). The SEP, on average, increased by about 0.17 °Brix for the unpeeled apples. Variety did not have a large effect on the model performance on sugar content predictions.

Randolph M. Beaudry

Papers

Effect of O2 and CO2 partial pressure on selected phenomena affecting fruit and vegetable quality.

Modified-atmosphere Packaging of Blueberry Fruit: Effect of Temperature on Package O2 and CO2

Harvest maturity, storage temperature, and 1-MCP application frequency alter firmness retention and chlorophyll fluorescence of 'Redchief Delicious' apples

Responses of horticultural commodities to low oxygen: limits to the expanded use of modified atmosphere packaging.

Determination of firmness and sugar content of apples using near-infrared diffuse reflectance