Technology

 

Food safety

‘Safety begins at home’, is something I learnt as a child. Well at Pres-Free safety begins with the home of the drying, it is here where we believe we have a significant differential from the usual dried fruits because we batch process we maintain the connection with the dryer. This motivates the dryer-operative to choose the best tastiest fresh fruit, for which they have skill, and make the best job of drying it with pride in their work which reflects in their bottom line. We charge a premium rate for the best tasting dried fruit, most of this goes to them.

The dryer operatives work within our approved guidelines and certifications. Our suppliers are inspected before we begin offering their fruit lines and at regular intervals afterwards.

Food safety continues at Pres-Free where we make some fundamental tests for moisture content, taste and micro-biological activity. Further safety checks are made maintaining the food standards of the packaging premises and packaging procedures. Final checks are made following packaging.

 

Natural Preservation

Sugar is the basis of fruit preservation, high sugar fruits like dates, grapes and prunes are the most common dried fruit because the high sugar content means you need to remove less water and so the process is more straightforward. However these natural fruit sugars are different to artificial sugars, most notable in the taste of the combination!

The moisture content of the dried fruit is a useful measure of dryness but the important value is what is called the ‘water activity’. This is the water that is free to help the microbes live and multiply. Quite a lot of water is firmly bound, for example to sugars.

Microbes are the opposition to preservation, they cause rot, and some rot makes us sick. By drying fruit we make an environment that they cannot multiply quicker than microbes naturally die. We can help keep the microbe level low by having clean fruit with low microbe level; this is ‘good house-keeping’ and selecting prime un-rotted fruit. Killing all the microbes with sulphur reduces their numbers the most.

Refrigeration is an ally in the fight against microbes by keeping their multiplication rate low; storage of most dried fruit around 5C is a good way of having a shelf life of years.

In Australia the fruit fly is a pest that has been kept at bay for decades, in dried fruit the eggs if they have survived drying process can be killed by a deep freeze for around about a day.

Natural preservation will lead to a good shelf life unless some microbes get past our defences; we make tests to protect against this. We quote a conservative shelf-life as a precaution against this happening.

 

Artificial Preservation and Drying

Preservation is most commonly carried out with sulphur especially for apricots; this has two big effects to kill microbes by forming dilute sulphurous acid and to break the cell walls, which increases rate of drying. The sulphur also helps colour the fruit and prevents oxidation, this is seen when low concentrations of sulphur species are used to preserve apple and banana and preventing the browning. However some asthma sufferers react badly to sulphur and it is not an environmentally friendly oxide. Low sulphur preservation using meta-bisulphites are used on many fruits and vegetables, other weak acids such as vinegar are also used to preserve, especially common for tomatoes. Sugar preservation is used commonly for tropical fruit such as mango and papaya and the taste of this product is so poor compared to natural preservation. However the process is double action, not only preventing microbes from multiplying but also carrying out some of the drying by osmosis. The ultimate sugar preservation of fruit is glace fruit, which has a long shelf life and is very sugary. Alcohol, ethanol, is another quite common preservative which both desiccates and preserves with the alcohol and fruit sugars and moisture forming a tasty liquor as well as preserved, often whole, fruit.