DATE PRESERVATION
DATE PRESERVATION
INTRODUCTION
Dates are marketed in two ways :
Les différentes étapes de conservation de la datte sont :
Dates are exposed to the risk of contamination by parasites, in particular mites, beetles, yeasts and molds. The product is usually fumigated with methyl bromide or phosphine.
However, these gases are highly toxic, difficult to handle and not compatible with organic farming.
What’s more, methyl bromide is banned in many countries because of its impact on the ozone layer. Phosphine degassing in the cold storage room destroys the copper components present in evaporators and air coolers.
Health regulations are constantly lowering acceptable levels of pesticide residues in foodstuffs. Microwave treatments have produced satisfactory results, but require the temperature of the date to be raised to 75°C. It should be noted that exposure to high temperatures alters the physico-chemical characteristics of this edible date fruit, thereby reducing its market value.
THE NEGATIVE COLD ALTERNATIVE
Without talking about freezing, the freezing temperature of a dry date is -16°C. The development of undesirable micro-organisms stops according to the cold scale.
Using the rapid cooling properties of our freezing tunnels, our equipment is capable of rapidly and evenly lowering the temperature of dates, from core to surface.
The process speed of a fluidized-bed tunnel, less than 10 minutes, ensures perfect sanitation of the fruit, while preserving its organoleptic properties. This time can be increased to several hours if the operation is carried out in a static tunnel (with no product movement).
Sorting the dates into homogeneous groups enables waste to be eliminated :
• Hard dates (need to wait for development)
• Soft date (requires high temperature for a short time)
• Ripe dates (no special treatment required)
• Dry dates (need hydration)
DATE CARE
Cleaning is necessary and important to ensure good quality of the finished product and to facilitate subsequent processing steps. It can be carried out by applying a flow of air through brushing, or by washing, which is the most common method.
There are several washing procedures, depending on the degree of dirt adherence and the consistency of the date. Consumers tend to prefer dates that are soft and fresh. The processor is committed to delivering quality merchandise with a sufficiently high water content, without losing the physical-chemical and organoleptic characteristics of the product. To achieve this, he hydrates the fruit if it is unripe. The quality operator must combine all parameters to obtain a quality product for the consumer.
GLUCOSE SYRUP
Glucose syrup forms a protective film around the hydrated date, increasing its sweetness and giving it a shiny, smooth appearance. The protective function of the glucose syrup film is to protect the date from contact with air. This protective film enables the date to retain its color and firmness, inhibiting the transfer of substances to the outside environment. It also helps to maintain water content and reverse the migration of sugars to the surface. In fact, the concentration of sugar at the surface increases considerably, activating the osmosis phenomenon and causing sugar to migrate inwards. Glucose is added at the temperature of the date, and the concentration of the soaking syrup varies according to the variety of fruit to be enrobed. Once the date has been soaked in the syrup, it must be drained immediately, before being dried to ensure its cohesion.
DRYING THE FRUIT
Drying is extremely important: its main aim is to reduce water content, thus inhibiting deterioration. The parameters to be controlled during drying :
• Temperature
• Air humidity
• Drying speed
• Drying time
Drying temperatures vary from one conditioner to another. In Tunisia, it is around 65° to 70°G, achieving dehydration and partial pasteurization at the same time. The effect of this temperature only comes into play when humidity is less than 50%. Below this relative humidity, dehydration occurs.
It should be noted that exposure to a high temperature, of the order of 75°C, significantly alters the physico-chemical characteristics and reduces the product’s market value.
THE PACKAGING STAGE
The date must be packaged to ensure, first and foremost, adequate protection to limit any possible deterioration in quality. This packaging must be gas, moisture and foreign particle. It must also provide adequate resistance during transport.
Plasticising is the last operation carried out in the packaging units before the product is dispatched for export or for sale on the local market. Storage must be carried out under controlled conditions to preserve the quality of the finished product.
A number of physico-chemical changes can occur during storage, such as :
• Drying out of moistened dates
• Rewetting of dry dates
• Fermentation
• Browning (color change)
CONCLUSION
Cold storage is essential to maintain the quality of processed dates. Tests carried out with a stabilized and fully ripe date at different temperatures are illustrated in this table:
Humidity control significantly extends date shelf life.
Dates are marketed in two ways :
- In bulk, without packaging, at a farmers’ market
- Conditioned and packaged, in a sales outlet or shipped from the importing country
Les différentes étapes de conservation de la datte sont :
1. Desinsectisation
2. Washing
3. Treatment by hydration and/or drying
4. Glucosage
5. Drying
6. Laminating
7. Packaging
8. Palletizing
9. Storage
10. Shipping
DEVELOPMENT2. Washing
3. Treatment by hydration and/or drying
4. Glucosage
5. Drying
6. Laminating
7. Packaging
8. Palletizing
9. Storage
10. Shipping
Dates are exposed to the risk of contamination by parasites, in particular mites, beetles, yeasts and molds. The product is usually fumigated with methyl bromide or phosphine.
However, these gases are highly toxic, difficult to handle and not compatible with organic farming.
What’s more, methyl bromide is banned in many countries because of its impact on the ozone layer. Phosphine degassing in the cold storage room destroys the copper components present in evaporators and air coolers.
Health regulations are constantly lowering acceptable levels of pesticide residues in foodstuffs. Microwave treatments have produced satisfactory results, but require the temperature of the date to be raised to 75°C. It should be noted that exposure to high temperatures alters the physico-chemical characteristics of this edible date fruit, thereby reducing its market value.
THE NEGATIVE COLD ALTERNATIVE
Without talking about freezing, the freezing temperature of a dry date is -16°C. The development of undesirable micro-organisms stops according to the cold scale.
Using the rapid cooling properties of our freezing tunnels, our equipment is capable of rapidly and evenly lowering the temperature of dates, from core to surface.
The process speed of a fluidized-bed tunnel, less than 10 minutes, ensures perfect sanitation of the fruit, while preserving its organoleptic properties. This time can be increased to several hours if the operation is carried out in a static tunnel (with no product movement).
Sorting the dates into homogeneous groups enables waste to be eliminated :
• Hard dates (need to wait for development)
• Soft date (requires high temperature for a short time)
• Ripe dates (no special treatment required)
• Dry dates (need hydration)
DATE CARE
Cleaning is necessary and important to ensure good quality of the finished product and to facilitate subsequent processing steps. It can be carried out by applying a flow of air through brushing, or by washing, which is the most common method.
There are several washing procedures, depending on the degree of dirt adherence and the consistency of the date. Consumers tend to prefer dates that are soft and fresh. The processor is committed to delivering quality merchandise with a sufficiently high water content, without losing the physical-chemical and organoleptic characteristics of the product. To achieve this, he hydrates the fruit if it is unripe. The quality operator must combine all parameters to obtain a quality product for the consumer.
GLUCOSE SYRUP
Glucose syrup forms a protective film around the hydrated date, increasing its sweetness and giving it a shiny, smooth appearance. The protective function of the glucose syrup film is to protect the date from contact with air. This protective film enables the date to retain its color and firmness, inhibiting the transfer of substances to the outside environment. It also helps to maintain water content and reverse the migration of sugars to the surface. In fact, the concentration of sugar at the surface increases considerably, activating the osmosis phenomenon and causing sugar to migrate inwards. Glucose is added at the temperature of the date, and the concentration of the soaking syrup varies according to the variety of fruit to be enrobed. Once the date has been soaked in the syrup, it must be drained immediately, before being dried to ensure its cohesion.
DRYING THE FRUIT
Drying is extremely important: its main aim is to reduce water content, thus inhibiting deterioration. The parameters to be controlled during drying :
• Temperature
• Air humidity
• Drying speed
• Drying time
Drying temperatures vary from one conditioner to another. In Tunisia, it is around 65° to 70°G, achieving dehydration and partial pasteurization at the same time. The effect of this temperature only comes into play when humidity is less than 50%. Below this relative humidity, dehydration occurs.
It should be noted that exposure to a high temperature, of the order of 75°C, significantly alters the physico-chemical characteristics and reduces the product’s market value.
THE PACKAGING STAGE
The date must be packaged to ensure, first and foremost, adequate protection to limit any possible deterioration in quality. This packaging must be gas, moisture and foreign particle. It must also provide adequate resistance during transport.
Plasticising is the last operation carried out in the packaging units before the product is dispatched for export or for sale on the local market. Storage must be carried out under controlled conditions to preserve the quality of the finished product.
A number of physico-chemical changes can occur during storage, such as :
• Drying out of moistened dates
• Rewetting of dry dates
• Fermentation
• Browning (color change)
CONCLUSION
Cold storage is essential to maintain the quality of processed dates. Tests carried out with a stabilized and fully ripe date at different temperatures are illustrated in this table:
| Storage temperature | Shelf life |
|---|---|
| 26/27°C | 1 month |
| 15/16°C | 3 month |
| 4/5°C (controlled RH) | 8 month |
| -2/-3°C | 1 year |
| -17/-18°C | More than 1 year |
Humidity control significantly extends date shelf life.