In a country marked by extreme weather that is on the higher side of the thermometer, any reference to frozen is usually greeted with a cool sigh. So if someone says that frozen food could be more nutritious than fresh food in certain cases, the statement need not be treated with disbelieving looks. Actually, there are many reasons why such a statement can be truly credible…
There are many myths about frozen food not being as good or as nutritious as fresh food. These myths need to be put into cold storage and frozen away forever. But first let’s address the problem about frozen versus fresh. What is fresh? Does it mean the food you are buying from your local supermarket or your friendly thelawallah?
Frozen food today is dictating the season’s trends for caterers, QSRs, hotel chains and even in home consumption. A step by step eye opener on the Individual Quick freezing (IQF) technology will help you do away with any myths and suspicion you may have regarding frozen food.
What goes into the process when vegetables and fruits are frozen to help them last longer, especially in a country like India, which is typified by a very hot climate. There are actually 12 stages before a vegetable or fruit is frozen. First is the reception of the raw produce (actually a misnomer because the product which is perfectly ripe is brought to the factory for freezing). That is because the produce will not ripen any further once it is frozen and therefore it is best to harvest the crop at its ripest. The other 11 stages are pneumatic cleaning, washing and de-stoning, visual inspection, trimming, shelling, sizing, pitting and skinning, blanching, cooling, sorting, individual quick freezing, grading, packing and storage.
The most critical stages are blanching and IQF. Once the produce has been cut it is essential to deactivate the enzymatic reaction which is triggered off by cutting the produce. Blanching adds to the shelf life without adding any preservatives to the product.
Raw material reception and manual sorting: IQF Processing does not change the physical characteristics of the raw products, therefore care is taken that inferior raw products are weeded out beforehand.
Pneumatic cleaning: In this part of the process the light foreign materials from the farms like leaves, twigs, and land particulate matter are separated. The waste is collected in a bag separately and disposed of periodically. Hydraulic washer and de-stoner: After the removal of light impurities by pneumatic cleaning, the heavy foreign bodies and stones are removed by means of a hydraulic de-stoner. By creating an upward water flow and passing the product over serrated belts, stones and other particles are separated.
Hydraulic washer and de-stoner: After the removal of light impurities by pneumatic cleaning, the heavy foreign bodies and stones are removed by means of a hydraulic de-stoner. By creating an upward water flow and passing the product over serrated belts, stones and other particles are separated. Combined with this unit is the washer with rinsing and flotation chambers to give the product a thorough wash in order to remove soil or secretions, etc. The water used for washing is continuously filtered and recycled. The product discharge net elevator is provided with a cleaning device, which guarantees the separation of all unwanted particles.
Inspection: After cleaning and washing, the product undergoes another visual check. Th e product is discharged over a non toxic plastic material belt on both sides of which people can stand and manually remove any visible bad product.
Preparation: Under this process, different functions are performed according to the type of product being handled. These include operations like peeling, de-husking, taking out the seeds, trimming to size, cutting florets, de-clustering, slicing, etc. The waste that is generated is collected at frequent intervals to avoid contamination of the product by building up of bacteria due to fermentation.
Blanching: After cleaning and cutting the raw material, it is essential to inactivate the enzymatic reaction which is initiated on cutting the product. This action is achieved in the blancher by heating the product in a definite time cycle up to a certain temperature for a certain time. The process of blanching may not be required for certain products, especially in the fruit category.
Cooling: The products out of the blancher is at approximately 80 to 85 degree Celsius. At such elevated temperatures, it cannot be taken to 20 degree Celsius without causing thermal shock to the product. It is important therefore to cool down the product to a temperature between 1 to 20 degree Celsius. Cooling also stops the deactivation process of the enzymes i.e. it ends the process of blanching.The “Water – product” movement comes about in the opposite direction so that the inlet of the hot product corresponds to a hot water outlet whilst at the discharge of the cooled product it corresponds to the inlet of cold water.
Sorting: This is the final check on the product and if any impurity has escaped the earlier checks it is detached and eliminated here.
Individual quick freezing: The final deep freezing is done in the IQF tunnel. A stainless steel spreader shaker uniformly loads and distributes products across the IQF belt. A vibrator beneath the belt initiates the fluidisation on products and assures 100 per cent separation without excessive agitation. Uniform air distribution through the product method of fluidisation can safely handle delicate and difficult products with minimum losses by elimination of abrasion of the products. By this method of freezing each individual part of the fruit or vegetable is frozen separately so that
even after attaining a temperature of -18 to -21 degree Celsius the pieces remain separated and do not form a block.
The IQF method of freezing ensures that the quality of the end product is much superior compared to other methods of food preservation like dehydration, canning or bottling as it as does not lead to any loss of nutrients, flavours, colours, shape or texture. The process also results in a longer shelf life (up to 18 months), reduces thawing loss and there is no product deformation.
Grading: Grading, after freezing, is required in some for the products to be sorted according to their physical dimensions as the market demand and prices for various sizes are different. To grade granular products such as peas and beans, a vibrating type of grader is used, which has an oscillating bed composed of various screens with different sizes as required. Now that we know what goes into making frozen food fresh, and that frozen food does not require preservatives always to keep it in good form, let’s eat it with less guilt and more relish.