Grape should be stored according to generally accepted rules – GOST 29181-91. This normative document involves all the rules and nuances of long storage: grape packing, required temperature and humidity conditions, fruits treatment and so on.
Grape varieties that are ideal for long storage
Grape storage is a complex process that requires the observance of certain temperature and humidity parameters. To preserve its initial shape, color and aroma, you will have to make much efforts. The first thing you need do to choose grape variety.
Storage life of table grape depends on its ability to keep the moisture. Many varieties of grape have thin skin that are not intended for long storage.
For storage it is better to choose variety of late ripening with large and strong berries. Specialists recommend to prefer the following varieties:
- Agadai. This grape variety is resistant to generation of bacteria and stored for 4 months.
- Asma is stored up to 5 months.
- Karabunru. This variety is also resistant to different deseases, however, in case of technology violation, storage life is reduced from 5 to 3 months.
- Muskat aleksandriyskiy preserves marketable conditions and useful qualities during 6 months.
- Muskat Hamburg is also one of the record holders for storage life.
Proper sorting is an important point that affects the storage life. Grape is usually sorted during gathering manually. The next one of the important stages is grape packing.
It is important! When packing, it is necessary to take care of grape desinfection. Close method of packing requires potassium metabisulphite. This antiseptic prevents the generation of harmful microorganisms.
Before loading to refrigerated chamber, racemation must be protected from direct sun rays and precipitation.
Technology of grape storage
Before loading the grapes, the refrigerated chamber is desinfected for 20 minutes with sulfur dioxide and adsorber SO2.
The optimum temperature for storage of table grape is from -1 °С to +1 °С. These are medium temperatrure parameters. In some cases the parameters are changed (depending on variety and climate conditions).
Humidity is not less than 90% and not above. It is important to provide a proper circulation of the air in order to avoid condensate formation. The blowing must be equal and quite intensive.
Features of storage the grape in the chamber with controlled atmosphere
Chambers with controlled atmosphere are widely used for storage of different vegetables and fruits, including grape.
For storage in chambers with controlled atmosphere, it is better to select the grape variety that comply with GOST 25896.
Ripeness is determined by:
- appearance, consistence, odor, taste;
- refrection coefficient of squeezed juice (the norm – 13-20);
- sugar-acid ratio (optimal rate – 18).
Berries must be hard, without cracks and damages. Grape is put into chamber with controlled atmosphere in a day after harvest. Chamber must comply with technical and sanitary parameters, approved by project and operational documentation.
Fumigation by means of sulphur dioxide is carried out after unloading the berries. This process lasts for 20 minutes.
Then the treatment is carried out once a month. After desinfection it is necessary to use the generator of gas environment.
After finishing the loading, the temperature in chamber with controlled atmosphere is increased up to +1 °С. The creation of optimal temperature of gas environment takes 5 days.
Composition of gas environment varies depending on variety. So, for such varieties of grapes as “Agadai“, “Taify pink”, “Nimrang”, “Asma“, carbon dioxide and oxygene ratio is 3-5% и 2-5% accordingly.
For such varieties as “Rizaga”, “Moldova”, “Italiya”, “Kara usum ashxabadskiy” are preferable the following parameters: carbon dioxide – 5-8%, oxygene – 3-5%.
When storing grape in the chamber with controlled atmosphere, it is also necessary to take into account several important points. Pressure should be within atmospheric to an accuracy of +250 Pa and humidity – 95%. Air circulation – periodic, ratio – 20 volumes/hour.
Profesisonal design and assembly of refrigerated chambers
Our company provides services for design and installation of refrigerated chambers for storage of different fruits and vegetables.
High qualified engineer designers after careful inspection and customer’s requirements (size and purpose of chamber, desired temperature condition) will provide all necessary project documentation (including estimation, specification, technical characteristics and equipment selection) and develop a project.
Then the works are carried out by installers of our company who have a great experience in the field of construction of refrigerated chambers and installation of specialized equipment.
Range of services is divided into the stages:
- design of refrigerated chamber (drawing up a cost estimate, sketch design, commercial offer, technical project, specifications);
- preparation of place for construction of chamber;
- assembly of refrigerated chamber (from sandwich panels with thickness of 120mm);
- installation and commissioning works of necessary equipment and ventilation system with recuperators;
- check of chamber for operability according to established parameters.
After installation you can conclude a contract for maintenance. So, you will extend the service life of your equipment for many years.
Diagnosis and timely replacement of parts are the warranty of efficient operation of refrigeration units. Regular maintenance will allow to determine even minor malfunctions and avoid expensive repair.