Recommendations For Maintaining Postharvest Quality
Shika Agblor, Postharvest Specialist, Native Fruit Development Program, University of Saskatchewan
Based on berry surface colour. Generally, red to purple fruit are ready for harvest.
Harvest in the cool of the day, early in the morning or late in the evening, when field temperatures are below 20°C. Minimize handling of fruit to avoid squashing. Machine harvested fruit deteriorate more quickly than hand-harvested fruit. Harvest fruit in shallow trays with slots at sides and bottom to facilitate heat removal. Such trays (eg. Fish and Farm Trays with dimensions 45 cm long x 33 cm wide x 9 cm high) can be obtained from Thunderbird Plastics Ltd., Vancouver, BC (Tel: 604-433-5624; Fax: 604-433-6231). Place fruit in shade and immediately start cooling. Remember, fruit are living tissue; they continue to respire after harvest. Respiration produces heat which causes loss of sugars and flavour.
Cool fruit down as quickly as possible to avoid flavour loss.; Rapid cooling in the field can be achieved by placing cryopak reusable ice substitutes over trays, if possible on the top and bottom of trays. Cryopak ice substitutes must be frozen prior to use; overnight freezing is often adequate. Cryopak ice substitutes are food-grade; They can be obtained from Cryopak Corporation, Vancouver, BC (Tel:1-800-667-2532 or 604-685-5143; Fax:604-685-9170).
Sort to remove twigs, leaves, defective, bruised and immature fruit. Fruit sorting is time-consuming. A fruit sorter (eg. air draft berry cleaner) equipped with a sorting table is manufactured by Hometown Machine, Sundre, AB (Tel:403-638-4646; Fax: 403-638-4649). The sorting table is 12 ft long and can accommodate 4-5 people on each side. If it is not possible to purchase one of your own, consider forming a co-operative with other fruit growers. The fruit sorter can be used for other fruit such as chokecherries, black currants, red currants, and blueberries. Sort fruit in a cool environment. This is necessary to help slow down fruit respiration. Ensure that fruit surfaces are relatively dry prior to storage. Wet fruit, which is usually due to dew condensing on the surface of fruit, can be removed by blowing air over fruit using an industrial fan. Fruit must be laid out in a single layer during drying to facilitate removal of surface moisture. Wet fruit is more susceptible to disease during storage.
For the fresh market: Wrap each tray containing fruit with plastic and place at 0°C; This temperature is critical for maintaining postharvest quality and extending the shelf life of saskatoons. Plastic material can be purchased through Unisource Canada, Saskatoon (Tel:306-931-8004; Fax: 306-931-7175) or directly from Winpak Ltd, Winnipeg (Tel: 204-889-1015; Fax: 204-832-7781) as a roll stock (PAE 2060 L) or as a stock pouch (VAK 3 L). This plastic material (1) restricts the amount of air coming in contact with the fruit and modifies the atmosphere around the fruit to about 2% oxygen and 5% carbon dioxide; (2) retains moisture so that there is no wrinkling of fruit; and (3) prevents microbial contamination. This method of wrapping plastic around fruit is known as modified atmosphere packaging. When this method is combined with low temperature storage, fruit respiration is slowed down and the shelf life of the fruit is extended. Ensure proper sealing of plastic. Improper sealing is detrimental to fruit quality. A home-style vacuum sealer (eg. a Food Saver Compact II by Tilia which can be purchased at any hardware store) is suitable. Modified atmosphere packaging can extend the shelf life of saskatoons by at least two weeks. Modified atmosphere packaging allows growers sufficient time to transport fruit to retail markets. Fresh fruit for retail markets can also be put in half-pint plastic containers and placed in cardboard boxes. Again, ensure that the boxes are wrapped with plastic and properly sealed. Store at 0°C.
For frozen fruit: Wrap each tray containing fruit with plastic and immediately place in a walk-in freezer at -20°C or -40°C. The lower the temperature of the freezer, the faster fruit will freeze.
Remember! Always transport fruit under cold storage.
Storage diseases can cause severe losses to saskatoon berries. The most common pathogen is Botrytis rot (grey mold). This fungus can grow at low temperatures. To minimize postharvest losses:
- Cool promptly
- Store at the lowest possible temperature (0°C recommended)
- Minimize bruising of fruit by handling as little as possible
- Remove all diseased or bruised fruit during sorting since the fungus can spread from diseased to good fruit
- Ensure good agricultural practices eg. good sanitation
Comments or questions?