Other Quality Changes

4.3.4.1.Titratable Acidity

Titratable acidity of the apples was measured in the 2003 season. The transfer of fruit from 0°C to the shelf life period at 20°C was observed to increase the rate of loss of

titratable acidity (Figure 4.12). However, exposure to 3 days at 20°C was not observed to cause substantial differences in ‘Cripps Pink’ apple titratable acidity (Figure 4.12).

Figure 4.12, The effect of temperature breaks (B - 3 days exposure to 20°C) in comparison to control fruit (C – 3 days at 0°C) on change of ‘Cripps Pink’ apple titratable acidity after 0, 2, 4, and 6 months storage at 0°C for optimal harvest fruit. 0, 2, 4, and 6 refer to 0, 2, 4 and 6 months storage at 0°C in air prior to exposure

respectively. After exposure fruit were returned to 0°C for 21 days followed by 14 days at 20°C. Empty bars represent time of exposure to 20°C for temperature break treatments whereas solid bars represent time at 20°C for all treatments (shelf life)

4.3.4.2.Weight Loss

The rate of weight loss for ‘Cripps Pink’ apples increased on exposure to 20°C, and was independent of storage duration before exposure (Figure 4.13), length of exposure (Figure 4.14a) or previous exposures (Figure 4.14b). Rates of weight loss for all treatments were observed to be similar, with a 3 day exposure to 20°C, resulted in an approximately 0.75% loss of fresh weight. The differences created by losing weight during exposure to 20°C were maintained throughout subsequent coolstorage. As a result the influence of temperature on weight loss can be considered additive as clearly demonstrated by the similar weight loss at the completion of storage of the two treatments exposed to two periods of 3 days at 20°C (2BS and 2BL) at different time periods (Figure 4.14b).

Figure 4.13, The effect temperature breaks (B - 3 days exposure to 20°C) in comparison to control fruit (C – 3 days at 0°C) on ‘Cripps Pink’ weight loss after 0, 2, 4, and 6 months storage at 0°C for optimal harvest fruit. 0, 2, 4, and 6 refer

to 0, 2, 4 and 6 months storage at 0°C in air prior to exposure respectively. After exposure fruit were returned to 0°C for 21 days followed by 14 days at 20°C. Empty bars represent time of exposure to 20°C for temperature break treatments whereas solid

bars represent time at 20°C for all treatments (shelf life).

Figure 4.14, Effect of (a) length of exposure time after 2 months storage at 0°C and (b) multiple breaks of 20°C for 3 days during storage on change in ‘Cripps Pink’ apple weight loss. Treatments CNT, Q0A, B0A and L0A represent exposure time of 0, 1, 3, and 6 days of exposure to 20°C. 2BS = 2 exposures (0 and 34 days); 2BL = 2 exposures (0 and 69 days) and 3BA = 3 exposures (0, 34 and 69 days). Data for CNT is

identical in both figures, although based on different reference times.

4.3.4.3.Disorder Incidence

An assessment of the internal and external storage disorders was conducted on the ‘Cripps Pink’ apples that were destructively assessed for quality attributes throughout the

2003 season. The incidence of ‘Cripps Pink’ storage disorders was largely influenced by storage duration, with those fruit stored for the longest period of time having the highest incidence of internal browning and superficial scald and hence total storage disorders. A single break of 3 days at 20°C did not influence of incidence of internal browning (Figure 4.15, Figure 4.16). However, significant differences (P < 0.05) in incidence of internal browning was observed in 2004 with those treatments with multiple exposures to 20°C (2BS, 2BL and 3BA) or a single long exposure (L0A) having signficantly less incidence of severe internal browning than those the treatments not exposed (CNT) or exposed for 3 days to 20°C (B0A), (Figure 4.16). This result should be treated with caution, as the numbers of fruit used in this assessment are small (30 fruit per treatment). This result of reduced internal browning disorders as a result of breaks in temperature mimics findings for the efficacy of intermittent warming treatments in reducing disorders in tomatoes (Artés et al., 1998), peaches (Fernández-Trujillo and Artés, 1997) and other fruit crops (section 2.1.1.1.3).

A break in temperature control (3 days at 20°C) significantly increased incidence of superficial scald for optimally harvested fruit stored for 6 months prior to temperature exposure (Figure 4.15a). This result is in contrast to previous findings where intermittent warming treatments successfully reduced superficial scald in the ‘Granny Smith’, ‘Cortland’, ‘Law Rome’ and ‘Delicious’ and ‘Pacific Rose’ cultivars (Watkins et al., 1995; Alwan and Watkins, 1999; Watkins et al., 2000a). Notably however, in the previously published studies, the lowest rates of superficial scald were obtained for fruit removed from cool temperatures on a weekly basis. In the 2004 harvest, little superficial scald was observed (section 3.3.4.3) and hence subsequent analysis of the treatment effect on incidence of superficial scald was not possible.

Figure 4.15, Percentage incidence of disorders for both 2003 harvests averaged over the entire length of time subsequent to the initial temperature break.

Figure 4.16, Incidence of disorders in 2004 treatments assessed after 175 days.

Treatment QOA was completed after 147 days (as opposed to 175 days) and hence not comparable to the other treatments due to the increase in rates of internal browning with

storage time (Figure 3.9g).

4.4. FURTHER DISCUSSION AND CONCLUSIONS

This investigation aimed to assess the effects of exposing ‘Cripps Pink’ apples stored at 0°C in air to short time periods at 20°C on the subsequent fruit physiology and quality changes on exposure to 20°C and on subsequent return to cool storage at 0°C. In investigating the response, the effect of harvest maturity, time in storage prior to exposure, length of exposure to 20°C and multiple exposures to 20°C were studied.

In the first section the effect of temperature breaks on fruit physiology will be discussed followed by a section discussing the effects of breaks in temperature control on fruit quality.

4.4.1. Effect of Breaks in Temperature Control on Postclimacteric ‘Cripps Pink’