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- Author or Editor: Christopher D. Gran x
`Red Delicious', `Golden Delicious', `Marshall McIntosh', and `Redmax McIntosh' apple (Malus domestica, Borkh.) fruit were sealed in low density polyethylene packages and stored at 0 to 25°C (3 to 25°C for `McIntosh' strains) until steady-state respiration occurred. O2and CO2 partial pressures for packages were determined, after which headspace EtOH samples were drawn from packages with a range of O2 partial pressures. The lower O2 limit for each variety over the range of temperatures was determined by elevated EtOH levels. As temperatures increased, the minimum O2 partial pressure at which EtOH accumulated increased. Temperature effects varied with cultivars. In the case of `Golden Delicious' the lower O2 limit (determined by EtOH accumulation) ranged from 0.57 kPa at 0° C to 0.80 kPa at 25°C, while for `Marshall McIntosh' low O2 limit values ranged from 1.2 kPa at 3°C to 6.4 kPa at 25°C. Macerated tissue EtOH levels mimicked headspace EtOH levels, and headspace accumulation of EtOH with time indicated active fermentation of tissues.
The oxygen partial pressure associated with the respiratory quotient (RQ) breakpoint (ie., lower oxygen limit) was determined for fruits of several apple cultivars stored at 0°C. Fruits were sealed in low density polyethylene pouches of various thicknesses and known permeability to determine O2 uptake, CO2 production, and respiratory quotients (RQ) at various O2 partial pressures. There were differences in the shape of O2 uptake versus steady state O2 curves between cultivars. While some cultivars showed steady declines in respiration rate from 8 kPa O2 to < 1 kPa, other cultivars showed no decline in respiration until O2 levels fell below 3 to 4 kPa. Fruits having elevated RQ values had greater levels of headspace ethanol in the polyethylene pouches, which confirmed anaerobic respiration. The lower oxygen limit ranged from a low of approximately 0.75 kPa for cultivars Northern Spy and Law Rome to high of 1.5 kPa for McIntosh.
Leaf removal has been reported to be beneficial to fruit quality of several grape cultivars. However, climatic conditions, time of leaf removal and genotype have a strong influence on the effect of leaf removal on fruit quality traits, such as soluble solids and titratable acidity. The effect of leaf removal on fruit quality of two vinifera grape cultivar grown in Minnesota was examined in this study. The first six basal leaves were removed from four canes on each vine of `Riesling' and `Chardonnay'. Leaf removal was carried out at two different times after the onset of verasion--early August (8/2) and late August (8/23). Fruit was harvested in late September and yield and fruit quality data were recorded. The results of the 1989 study will be discussed here. Leaf removal did not significantly affect yields obtained from either cultivar, regardless of leaf removal date. Early leaf removal on `Chardonnay' vines resulted in significantly higher soluble solids and significantly lower titratable acidity than that observed for fruit of control or late removal treated vines. Similar results were observed for `Riesling', however the differences were not significant. Data from 1989 and 1990 will he presented and discussed in the talk.