Jujube quality management

Page last updated: Monday, 10 August 2020 - 11:49am

Please note: This content may be out of date and is currently under review.

This page aims to assist growers to consistently deliver quality jujubes to consumers.

Introduction

To maximise profits, jujube quality should be managed from selection of the orchard site through to transport to the market. There are many factors throughout production that will influence the quality of the product including:

Variety selections
Quality of propagating material
Irrigation and nutrition management
Training and pruning
Pest and disease control
Harvest
Postharvest storage, packaging and transport

Variety selections

There are currently around 15 jujube varieties grown in Australia. Some are fresh eating varieties, some are best for drying or processing while others are multipurpose. Selecting the right variety for your end product will be an important factor in the final quality of your fruit. Table 1 outlines the varieties available in WA and their best use.

The quality of the propagating material will also influence fruit quality. Detecting and treating diseases in nursery stock will ensure good quality planting material for the industry.

Planting a mixture of varieties with different maturity times will allow you to extend your season and manage at peak times such as harvest.

Table 1 Jujube varieties in Australia
Variety	Use	Characteristics
Li	Fresh	Large, mid-season ripening
Chico	Fresh	Fruit is round but flattened Excellent fresh fruit with an apple-like sweet-acid taste Good either fresh or dried Mid-late season ripening
Shanxi-Li	Fresh	Very large fruit
GA866	Fresh	Sweet fruit with a high sugar level Large, elongated fruit
Redlands	Fresh	Very large, sweet, round fruit Mid-season ripening
Silverhill	Fresh	Med-large, elongated fruit, very sweet Very late season ripening Good for humid areas
Sherwood	Fresh Dried	Fruit is very dense and excellent quality Late season
Honeyjar	Fresh Dried	Small but very unique, sweet tasting, crunchy, juicy fruit, very thin-skinned Early ripening Considered a fresh eating jujube but also good dried
Sihong	Fresh Dried Processed	Excellent, large, round fruit Mid-season ripening One of the best fresh varieties Also good processed or dried
Suimen/ Shuimen	Fresh Dried Processing	Fruit is elongated Fairly good fresh but better dried or processed Mid-season ripening
Lang	Dried Processing	Large, pear-shaped fruit Mid- late ripening Good variety for dried fruit, very good for processing Not suited for humid areas The tree is very upright and virtually thornless
Don-Polenski	Dried	Similar to Lang with a better, crisper flavour
Thornless	Dried	Fruit similar to Lang
Admiral Wilkes	Dried Processing	Elongated and very late ripening Best processed or dried

In the orchard

Irrigation

Irrigation is an important factor for producing a good yield of quality jujubes. Irrigation scheduling has a direct impact on tree health and fruit yield as well as size and quality. Without correct scheduling an orchard is more susceptible to nutrient deficiencies, physiological disorders, pests and diseases.

See Jujube irrigation recommendations for more information.

Nutrition

Correct nutrition of jujube trees is essential if they are to crop and perform to their maximum potential. Annual leaf analysis in January (or 10 weeks after flowering) is essential to develop a fertiliser program for your orchard. Soil analysis can also be a good insight into soil fertility and pH. Excessive or insufficient fertiliser application can cause problems that will affect fruit quality.

See Jujube fertiliser recommendations for more information.

Training and pruning

Trees should be trained to develop a strong structure and fill their allotted space as quickly as possible with canopies that facilitate for efficient management (e.g. spraying, harvesting etc.).

Jujube trees need to be pruned annually to enable the tree to bear a full crop. Thinning and removal of damaged and diseased wood also improves pest and disease control.

Pest and disease control

Diseases and insect pests need careful management to prevent poor fruit set, misshapen fruit and skin and flesh damage. Efficient management relies on regular monitoring of your orchard. Pest populations should be kept below levels that will cause financial losses but must meet legal pesticide residue regulations.

Pest monitoring should be conducted on a weekly basis and recorded. You should keep a record of all chemicals used, dates and rates of applications. Percentage losses from insect and disease damage should also be recorded at grading after harvest.

Maturity

Jujube fruit matures from February to May in Western Australia (based on currently grown cultivars). Immature fruits have green skin and will not ripen if picked. Fruit picked later will continue to ripen after harvest. The fruit can be left on the tree to be picked when dried.

Fruit maturation of Chinese jujube can be divided into three phases based on colour, flesh firmness and composition (starch, sugar, acid, water):

White mature: The fruit is near full size and shape; the skin of the fruit is thin and changes from green to greenish white in colour. Flesh becomes white and loose with less juice and sugar and more starch.
Crisp mature: The fruit skin is half to fully red in colour, becomes thicker, harder and easily separated from the flesh which becomes crisp, juicy and sweet, containing more sugar and acid.
Fully mature: Sugar content of the flesh increases rapidly and water content begins to decrease. The flesh near the stone and fruit stalk becomes yellow and soft. The skin changes to a dark red and fruit becomes wrinkled.

The three stages of jujube maturity: a) White mature; b) Crisp mature and; c) Fully mature

Harvesting

The proper harvesting time depends on the end use of the fruit (fresh consumption, dried or processed). For fresh consumption jujubes should be picked at the crisp mature stage to prolong storage life. Fruits to be dried should be picked when fully mature and fruits for candying should be picked at the white mature stage.

Fruit harvested for fresh consumption is usually hand-picked. Fruit that is dried can be left on the tree until it drops or harvested by shaking the tree or branches.

Harvest jujubes early in the morning when temperatures are cool. The higher the temperature of the fruit, the greater the need for refrigeration for cooling and the greater the cost.

Fruit should be as free as possible from breaks, bruises, decay and other damage which increases moisture loss and provides entry points for bacteria and fungi.

Before transport to a packing shed, ensure fruit is kept in the shade in a shed. Jujubes should be transported with a cover to the packing shed within a few hours of harvesting.

Dried jujube fruit can be obtained by drying under the sun for about 3 weeks or in a cabinet drier at 60℃ for 36-48h until the moisture content reduced to less than 25%.

Fruit quality testing

It is important to pick jujubes at the correct maturity and size for marketing. Requirements for local and overseas markets often differ.

Total soluble solids is an internal maturity parameter that should be tested. Sugar levels are a commonly used measurement in a wide range of crops.

The sample you test should be typical of what you are planning to pick. Pick at least 10 pieces of fruit (the more fruit you pick, the greater the accuracy of your results). Pick fruit from at least 10 trees across the block and from all sides of the trees. If you have more than one variety then you should test these separately.

The percentage sugar, measured in degrees Brix (°Brix), indicates the sweetness of the fruit by measuring the number of soluble solids in the juice. A hand-held refractometer can be used to measure total soluble solids (percentage sugar/°Brix).

Figure 2 shows total soluble solids of jujube fruit grown in WA. The variety Li had the highest level of total soluble solids (31°Brix) of the three varieties tested and Chico had the lowest (25°Brix).

Figure 2 Total soluble solids percentage sugar or °Brix) of three jujube varieties grown in Western Australia

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.

Table 2 Effect of maturity at harvest on storage times
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).

Table 3 Atmospheres for long term CA and suggested fruit maturity and packaging
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).

Table 4 General grading standard for fresh jujube
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

Table 5 Grading standard for dry jujubes
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

Aston, R 2006 ‘Jujube – the Chinese Date’, Third Millenium Publishing, Available from: http://www.3mpub.com/ashton/title3.html

Victoria Department of Agriculture & Australian Horticultural Corporation 1993, ‘Guide to quality management: apples’, Australian Horticultural Corporation, Melbourne: Dept. of Agriculture (Vic.), Sydney

He, RP, Li, J, Zhao, F, Kong, WN and Niu, RS 2009 ‘Study on fruit quality of jujube varieties during maturity’ Acta Hort. (ISHS) 840: pp 553–556.

Liu, M. 2006 ‘Chinese jujube: Botany and horticulture’ Horticultural Review, Volume 32 (ed J. Janick), John Wiley & Sons, Inc., Oxford, UK.

Liu, M, Wang, M (chief editors) et al 2009 ‘Germplasm resources of Chinese jujube’. China Forestry Publishing House. Beijing, China.

Sheng, J, Yunbo, L and Shen, L 2003 ‘Storage of Chinese winter jujube fruit’ Proc. XXVI IHC – Asian Plants, Acta Hort. 620 ISHS, pp 203–208.

Yan, G and Ferguson, AR 1993 ‘The Chinese date or Chinese jujube’ Horticulture in New Zealand, vol 4 number 2, pp 13–18.

Zhang, H, Jiang, L, Ye, S, Ye, Y and Ren, F 2010 ‘Systematic evaluation of antioxidant capacities of the ethanolic extract of different tissues of jujube (Ziziphus jujuba Mill.) from China’ Food and Chemical Toxicology 48, pp 1461–1465.

Zhu, X.J. 2008 ‘Research progress of influencing factors and fresh-keeping technique of ‘Dongzao’ jujube storage’, J Anhui Agric Sci, 36 (14): 5864-5865

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