The timing of harvest is largely determined by status of the fruit with colour, gloss, size and sugar-acid ratio used as indicators. A lower sugar ratio may be used as the harvest index depending on the cultivar (Table 3.3).
Table 3.3 Sugar ratio and maturation period harvest index (NPQS 2011).
Cultivar
|
Sugar content (Brix)
|
Time taken to reach maturity after full bloom (days)
|
Campbell Early
|
14
|
75–80
|
Delaware
|
17
|
60–65
|
Kyoho
|
17
|
90–95
|
Muscat Bailey A
|
19
|
110–120
|
Fruit is harvested in the morning if the weather is sunny. Grape bunches are cut from the plant with pruning scissors and stored in a harvest box. Fruit is not packed too tightly to prevent berries from dropping or clusters becoming damaged, and is generally piled 2–3 levels high (Figure 3.19). Harvested fruit is stored under shade to keep it cool until it is transferred to the packing house (NPQS 2011).
Figure 3.19 Plastic harvest boxes (left) and fruit piling method (right) (NPQS 2011)
1.10Post-harvest
1.10.1Packing house
Pre-cooling and sorting
Fruit is pre-cooled following harvest.
Using pre-cooling boxes, fruit temperatures are dropped from 30 °C to 4–5 °C by forced air cooling for 4–6 hours, or by static pressure air cooling for 1–2 hours (NPQS 2011).
Trained sorting experts supervise the sorting process (NPQS 2010b).
Any damaged, unripe, small or dehiscent berries or bunches are removed during sorting. Grapes are manually sorted by quality and the size of berries (Figure 3.20).
Figure 3.20 Grape sorting process in packing house (left and right), sorting by quality and size of berries and removing unsuitable fruits (NPQS 2011)
Packing and storage
Packing is carried out to minimise damage to fruit while being convenient for transport and sale. Grapes are packaged in corrugated cardboard boxes holding 4–10 kg (Figure 3.21) (NPQS 2011). These boxes are designed to prevent pest entrance and those with vent holes are covered with vinyl after packing to prevent pest entrance (NPQS 2010b). Grapes are placed in cold storage prior to export at 0 C to -5 °C ± 0.5 °C and 80–90% humidity (NPQS 2011).
Figure 3.21 Grape packing for export (left). Packaging consists of corrugated cardboard box with paper inner packaging (right) (NPQS 2011)
Figure 3.22 summarises the post-harvest packing house, storage and distribution steps for Korean table grapes produced for export.