Fruit Physiological Disorders

Stonefruit: Internal Breakdown (Chilling Injury)

H. Crisosto and E. J. Mitcham. UC Davis Postharvest Specialists.

Flesh Translucency and Bleeding in Plum

Importance: Chilling injury (CI) or Internal breakdown (IB) is the main limiting factor in the shipping and consumption of peaches and nectarines. This is the most frequent complaint by consumers and wholesalers and the main barrier to consumption.

Symptoms: Loss of flavor, ‘off flavor’, lack of juiciness due to leathery texture or flesh mealiness (), black pit cavity, and flesh browning (FB). In plum and pluots, in addition to the previous symptoms, flesh translucency and red pigment accumulation (bleeding) are typical.

Causes: CI is triggered when fruit are stored below 8°C. Onset of symptoms is more rapid and severity of symptoms greater when fruit are exposed to temperatures between 2 and 8°C (36 and 46°F) (the ‘killing temperature range’). CI symptoms normally appear after fruit are moved from cold storage to room temperatures and while some ripening is occurring. For this reason, this problem is usually experienced by consumers, not the grower and/or packer. Stone fruit cultivars vary greatly in susceptibility to CI and some of them do not develop symptoms. In most cases, early-season peach and nectarine cultivars are least susceptible and late-season cultivars are most susceptible. Among plum cultivars, there is no seasonal pattern of susceptibility. Recently developed cultivars in the market from different breeding programs are showing less susceptibility to CI.

Control:

• The long-term solution is to breed cultivars using genomic tools that are not susceptible to CI. This work is in process, pursued by a multistate effort (RosBREED).

In the meantime, follow these guidelines:

• Market susceptible cultivars according to their potential postharvest life.
• Use the controlled-delayed-cooling (‘preconditioning’) treatment to delay onset and reduce intensity of CI symptoms. When this ‘preconditioning’ protocol is executed properly, fruit postharvest life almost doubles.
• Storing below 0°C (32°F), but above the freezing point, and avoiding the ‘killing temperature range’ 2 to 8°C (36 to 46°F) are beneficial to delay CI symptoms and extend market life.
• Enforce proper postharvest practices during handling, transportation and retail handling. Keep fruit near 0°C (32°F) during storage and transportation, and avoid fruit exposure to temperatures between 2 and 8°C (36 and 46°F) (‘killing temperature range’) during transportation and retail handling.
• Educate fruit handlers (warehouse, retail handlers and consumers) on how to reduce CI incidence and intensity.

Flesh Browning in Plum - Photo by Carlos Crisosto

Mealy and Brown Peach - Photo by Carlos Crisosto

Mealy Fruit - Photo by Carlos Crisosto

2020