Post-harvest
Cool storage
Cool storage reduces the rate of respiration and ripening and is essential to provide quality jujubes for up to 3 months. Fresh jujube fruit cannot be stored for a long period under ambient conditions due to its perishable nature. Controlled Atmosphere (CA) storage has been shown to further increase storage quality of jujubes.
The maturity of jujubes at harvest will affect the quality of fruit after storage. Table 2 shows that white mature fruits will have the longest storage time.
| Maturity at harvest | Storage time |
|---|---|
| White mature | >3 months |
| Crisp mature (half red) | 1–2 months |
| Ripening stage (fully red) | <1 month |
Table 3 Summarises suggested conditions for CA storage of jujubes. Semi-red (crisp mature) jujubes can be kept crisp for over 100 days if packed in 0.04–0.07mm vented polyethylene bags and stored at 0±1°C (Liu 2006).
Jujube fruit stored at -2.2 to 2.5 °C, 90% relative humidity (RH), 19.4% O2, and 0.05% CO2 in a container sealed with 1 to 2 layers of polyethylene film showed the best results at the end of postharvest storage (Sheng et al. 2003).
Another study found that in order to keep fine fruit rate above 92% when stored over 120 days it is recommended to: harvest when fruit is 25–50% red; store the fruit at -2.5–3.5°C (which is about 1–2°C higher than the freezing point -4.71°C); and pack in vented polyethylene bag plus a CO2 absorbent (for example, hydrated lime) and; the O2/CO2 ratio maintained at a certain level, approximately 19:0.2 % (Sun et al. 2009).
| Maturity at harvest | Temp (°C) | CO2% | O2% | RH (%) | Packaging | Storage (days) |
|---|---|---|---|---|---|---|
| - | -2.2−2.5 | 0.05 | 19.4 | 90 | Container sealed with 1−2 layers of polyethylene film | Long term |
| 25−50% red | -2.5−3.5 | 0.2 | 19 | - | Vented polyethylene bag and CO2 absorbent | 120 |
| semi-red | 0±1 | 5 | - | 90−95 | 0.04−0.07mm vented polyethylene bag | 100 |
Freezing
Chinese jujube can be freeze-dried or frozen, although flesh firmness and fruit quality tends to decline. Faster freezing time results in higher fruit firmness retention. Long-term storage of jujube fruits can be achieved by freezing the fruits in low temperature liquid media (CaCl2 solution) and keeping the frozen fruits below -22°C.
Sorting and grading
Jujubes should be sorted and graded before marketing in order to maintain a consistent, high quality product for consumers.
Remove any jujubes with insect damage, disease, disorders, cracks, sunburn, blemishes, handling damage and any poorly shaped or undersized fruit.
Jujubes should ideally be graded into variety and size grades. As the varieties such as Li and Chico have such a different size and shape as well as different flavours they should be sorted into separate packaging.
It is important to record rejections from sorting and type of damage. Keep a record of your packout (e.g. number of cartons/bags) and work out the percentage lost.
Tables 4 and 5 below outline some general guidelines for grading standards of fresh and dry jujubes (based on information from China).
| Grade | 1 | 3 | 3 |
|---|---|---|---|
| Weight (per fruit) | ≥20g | 16-20g | 10-16g |
| Shape | Spherical or oval (depending on variety) Uniform | Spherical or oval (depending on variety) Uniform | Spherical or oval (depending on variety) Uniform |
| Defects | None | No disease or pest damage ≤3% split fruit | No disease or pest damage ≤5% split fruit |
| Colour | >30% red | >30% red | >30% red |
| Taste | Crisp, tender, juicy, sweet | Crisp, tender, juicy, sweet | Crisp, juicy, sweet
|
| Grade | Premium | 1 | 2 | 3 |
|---|---|---|---|---|
| Shape and size | Uniform ≤300 fruit/kg Standard variety characteristics | Uniform ≤360 fruit/ kg Standard variety characteristics | Uniform ≤420 fruit/ kg Standard variety characteristics | Normal shape Standard variety characteristics |
| Quality | Plump flesh, bright red, dry Impurity ≤0.5% | Plump flesh, bright red, dry Impurity ≤0.5% | Plump flesh, bright red, dry Impurity ≤0.5% | Flesh uneven, dry ≤10% fruit with uneven colour Impurity ≤0.5% |
| Mechanical injury and blemish | No disease or pests ≤3% split, blemished or immature fruit | No disease or pests ≤5% split or blemished fruit | No disease or pests ≤10% split or blemished fruit | No disease ≤15% split or blemished fruit Insect damage ≤5%. |
| Moisture content | ≤28% | ≤28% | ≤28% | ≤28% |
Packing and packaging
Along with cool storage, suitable packaging can facilitate handling, protect the produce, extend storage/shelf life and help to maintain good quality fruit.
Choice of packaging will depend on customer requirements, market locations and fruit quality. There are several types of packaging used for jujubes including cartons and trays as well as plastic punnets.
Packaging should be designed to protect fruit from damage and bruising during transport and storage as well as have adequate ventilation. Presentation and labelling are important market considerations to attract customers.
Summary
There are many factors along the supply chain that will influence the quality of jujubes. Keeping detailed records of nutrient applications, irrigation, pests and diseases, final packout and wastage will help you to identify areas for improvement in your production and quality of your product.
Acknowledgements
This work was supported by AgriFutures Australia and the WA Jujube Growers Association.
References
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