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O.L. Lau

Tolerance of apples to low levels (0.5%) of O2 was cultivar-dependent. `Spartan' (SP), `Delicious' (RD), and `Golden Delicious' (GD) apples (Malus domestica Borkh.) held for 7 months in 1.0% O2 (with 1.5% CO2) at 0.5C, plus ≈2 months in air at 0C and 7 days in air at 20C, were similar to those held in 1.5% O2. However, incidence of skin injury in fruit held in 0.5% O2 was very high in SP (purple-brown discoloration), low in RD (purple-brown discoloration), but only negligible in GD (lesions). Skin discoloration in SP and RD developed rapidly in air at 20C. Holding in 0.5% O2 improved retention of flesh firmness and juice acidity in GD and, under certain conditions, reduced scald in RD and SP, delayed yellowing in GD, but increased flesh breakdown in SP, flesh browning and alcohol flavor in SP and RD, and core browning in RD.

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O.L. Lau

Incidence of scald in nontreated and DPA (2000 mg·liter-1)-treated `Delicious' apples (Malus domestics Borkh.) was assessed after 8.5 months in 1.5% or 0.7% O 2 plus 1.5% CO2 at 0.2C, with and without C2H4 scrubbing. Incidence of scald was high in non-DPA fruit held in 1.5% O2, and DPA treatment reduced scald in fruit held in 1.5% or 0.7% O2. Scald control was better with 0.7% O2 and no DPA `treatment than with 1.5% O 2 and a DPA dip. Ethylene scrubbing had no effect on scald in fruit held in 0.7% or 1.5% 02. Susceptibility of fruit to scald-and flesh browning exhibited seasonal variation, which was related to the differences in fruit maturity and the amount of watercore at harvest, respectively. Chemical name used: diphenylamine (DPA).

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O.L. Lau

In a 2-year study, the benefits and risks of an initial low O2 stress treatment (ILOS; 0.04 kPa O2 for 10 days) as a supplement to 1.5 or 0.7 kPa O2 storage for controlling scald in `Starkrimson Delicious' apples (Malus ×domestica Borkh.) were evaluated. The fruit were picked from 15 orchards and harvested over five successive weeks to generate a wide range in maturity. Storage in 0.7 kPa O2 did not adequately control scald in fruit picked at starch index between 1.0 and 2.1 (10% to 35% scald), but reduced watercore-induced breakdown in fruit picked at starch index ≥2.4 (0–9 scale). The ILOS treatment gave a statistically significant but commercially nonsignificant scald control benefit to fruit held in 1.5 kPa O2 in 1 year, but not to fruit held in 0.7 kPa O2. ILOS did not increase alcoholic taste, but increased skin purpling in 0.7 kPa O2-stored fruit from the final harvest in 1 year. ILOS decreased flesh firmness in fruit picked at starch index ≥1.7 and increased watercore-induced breakdown in fruit picked at starch index ≥2.1 in both years.

Free access

O.L. Lau

In a 3-year study, the effectiveness of 0.7% and 1.5% O2 to attenuate scald was evaluated on three strains of `Delicious' apples (Malus ×domestica Borkh.)—`Harrold Red', `Starking', and `Starkrimson'—harvested five times at weekly intervals from a wide range of orchards. Scald susceptibility of fruit held in air, 1.5% O2 + 1.0% CO2, and 0.7% O2 + 1.0% CO2 at 0 °C decreased sharply as the fruit matured on the tree (starch index 1.0 to 2.5 on a 0 to 9 scale). Later harvests (starch index >2.8) further reduced scald but the fruit had more watercore-induced breakdown and were 3 N softer than fruit picked at a less advanced maturity. Early picked `Starkrimson' (starch index <2.0) scalded more than `Starking' and `Harrold Red' in air, 1.5% O2, and 0.7% O2 storage at 0 °C, and 0.7% O2 was less effective than 1.5% O2 in scald control. While 0.7% O2 storage effectively reduced scald (less than 10%) for 8 months in `Starking' and `Harrold Red' picked over a wide range of maturity (starch index 0.7 to 4.3), it did not adequately control scald (up to 45%) in early picked `Starkrimson' (starch index <2.0). Storage in 0.7% also reduced watercore-induced breakdown in `Starkrimson' (starch index >3.0) and did not result in skin purpling or alcoholic taste in `Harrold Red', `Starking', and `Starkrimson'.

Open access

O. L. Lau

Abstract

In a 3-year study, commercially produced ‘Spartan’ and ‘Delicious’ (Malus domestica Borkh.) apples held at 1.5C in a 1.5% O2 + 1.5% CO2 controlled atmosphere (CA) with a high level of C2H4 (0 μl·liter-1 initially and gradually increased to 1173 μl·liter-1) retained a satisfactory level of flesh firmness for 9 to 10 months. Maintaining a low level of C2H4 (<1.0 μl·liter-1 during the first 3 months of storage and rising to 6.3 μl·liter-1) in the 1.5% O2 + 1.5% CO2 storage atmosphere did not improve the retention of flesh firmness in these two cultivars and, on many occasions, led to a small decrease in flesh firmness in ‘Spartan’ apples. Low-C2H4 storage augmented the effect of diphenylamine in reducing scald in ‘Delicious’ apples in 1 year during shelf-life test, but also increased the incidence of coreflush in ‘Spartan’ apples in 1 year during poststorage holding in air at 0C and during subsequent shelf-life test.

Open access

O. L. Lau

Abstract

‘McIntosh’ apples (Malus domestica Borkh.) held at 1.5C in a high–C2H4 (374 µl·liter−1), 2.2% O2 + 3.0% CO2 atmosphere were seldom softer than fruit held in a low-C2H4 (1.7 µl·liter−1) atmosphere with the same levels of O2 and CO2. Scrubbing of C2H4 is not cost-effective in maintaining dessert quality of ‘McIntosh’ apples in commercial controlled-atmosphere storage.

Open access

O. L. Lau

Abstract

‘Golden Delicious’ apples Malus domestica Borkh.) stored well commercially at OC in a 1.0% to 1.5% O2 + 1.5% CO2 atmosphere established by a rapid controlled atmosphere (CA) procedure (Lau, 1985). The observation that firmness of ‘McIntosh’ apples after storage in 2.5% to 3% O2 can be improved by reducing C2H4 (Forsyth et al., 1969; Liu, 1977) has generated considerable interest in the Pacific Northwest in using low C2H4 atmosphere to improve storage quality of ‘Golden Delicious’ apples. This 3-year study evaluated whether reduction of C2H4 in a rapidly established 1.5% O2 + 1.5% CO2 storage atmosphere could improve the quality and suppress the C2H4-forming enzyme (EFE) activity of ‘Golden Delicious’ apples.

Open access

O.L. Lau

Abstract

In a 4-year laboratory and commercial study, ‘Golden Delicious’ and ‘Delicious’ apples (Malus domestica Borkh.) stored in 1.0% to 1.5% O2 + 1.0% to 1.9% CO2 at 0° to 0.5°C and 90% to 92% RH for 6 to 10 months maintained a higher firmness and acid level than apples stored in standard commercial atmospheres of 2.5% O2 + 1.0% to 1.5% CO2 at 0°. Fruit stored in 1.0% to 2.5% O2 with a rapid CA procedure were firmer than those with a slow CA procedure. There was no fruit injury or increased alcohol or off-flavor production resulting from the 1.0% to 2.5% O2 + 0.5% to 2.0% CO2 storage atmospheres established by the rapid CA procedure. Reduction of storage CO2 from 2.0% to 0.5% did not affect the firmness of ‘Delicious’ apples kept in 1.0% or 2.5% O2, but appreciably reduced firmness of ‘Golden Delicious’ kept in 2.5% O2 and to a lesser extent in 1.0% O2.

Open access

O.L. Lau

Abstract

‘Spartan’ apples (Malus domestica Borkh.) kept in 1.0% O2 + 2.0% CO2 at 0°C for 6–9 months were firmer and had more acids than apples kept at standard commercial atmospheres of 2.5% O2 + 2.0% CO2. The high firmness and juice acidity associated with low O2 atmospheres persisted for 7 days in 20° air. Reduction of storage CO2 from 2.0% to 0.5% appreciably decreased firmness and increased incidence of core browning and scald in fruit stored at 2.5% O2 but not in those stored at 1.0% O2. No fruit injury or increased alcohol or off-flavor production resulted from the low O2 treatments; reduction of storage O2 from 2.5% to 1.0% decreased core browning in the fruit. Fruit stored in 1.0% to 2.5% O2 with a “rapid CA” procedure were firmer than those with a “slow CA” procedure immediately after removal from the storage, but this benefit disappeared in fruit from the 1.0% and 1.5% O2 atmospheres after an additional storage period of 28 days in 0° air and 7 days in 20° air.

Open access

O.L. Lau

Abstract

Commercial applications of a “rapid CA” procedure (short loading time and rapid reduction of storage O2 to 2.5%) significantly improved retention of flesh firmness and juice acidity in controlled-atmosphere (CA)-stored apples from a wide range of production regimes. ‘Golden Delicious’ and ‘McIntosh’ apples responded more to the rapid CA procedure than did ‘Spartan’ or ‘Delicious’ apples. Rapid CA maintained fruit firmness of ‘Golden Delicious’ and ‘Spartan’ apples picked over a wide range of maturities and reduced the susceptibility of ‘Golden Delicious’ apples to bruising.