Saturday, 12 May 2012

Frozen Foods

By: Shoaib Awan
Freezing preservation retains the quality of agricultural products over long storage periods. As a method of long-term preservation for fruits and vegetables, freezing is generally regarded as superior to canning and dehydration, with respect to retention in sensory attributes and nutritive properties. The safety and nutrition quality of frozen products are emphasized when high quality raw materials are used, good manufacturing practices are employed in the preservation process, and the products are kept in accordance with specified temperatures.
The proportion of fresh food preserved by freezing is highly related to the degree of economic development in a society. As countries become wealthier, their demand for high-valued commodities increases, primarily due to the effect of income on the consumption of high-valued commodities in developing countries. The commodities preserved by freezing are usually the most perishable ones, which also have the highest price. Therefore, the demand for these commodities is less in developing areas. Besides, the need for adequate technology for freezing process is the major drawback of developing countries in competing with industrialized countries. The frozen food industry requires accompanying developments and facilities for transporting, storing, and marketing their products from the processing plant to the consumer. Thus, a large amount of capital investment is needed for these types of facilities. For developing countries, especially in rural or semi-rural areas, the frozen food industry has therefore not been developed significantly compared to other countries.
The quality of the frozen food products, specially in warm countries, is mainly based on factors like how the processing has been carried out, how was the storage temperature, how well the transportation facilities were present and how has been the packaging. In the Pre-process of freezing the most important step is blanching. Blanching is the exposure of the vegetables to boiling water or steam for a brief period of time to inactivate enzymes. Practically every vegetable (except herbs and green peppers) needs to be blanched and promptly cooled prior to freezing, since heating slows or stops the enzyme action, which causes vegetables to grow and mature. After maturation, however, enzymes can cause loss in quality, flavour, colour, texture, and nutrients. If vegetables are not heated sufficiently, the enzymes will continue to be active during frozen storage and may cause the vegetables to toughen or develop off-flavours and colours. It destroys some bacteria and helps remove any surface dirt.
In Pakistan most of the industries use Hot Water Blanching. In this type of blanching the vegetables are simply submerged in the hot water for a specific period of time and temperature. But in Pakistan most of the Vegetable freezing industries do not even have a blancher and if some have they do not have any mechanism to control the time and temperature. As the blanching process is meant to de-activate the enzymes which cause spoilage but if the process is not adequate enough then how one can ensure product quality. The research have shown that if the blanching process has not been carried out properly then one can not control spoilage and microbial growth even if the product was stored under -18oC.
The enzymes used as indicators of effectiveness of the blanching treatment are peroxidase, catalase, and more recently lipoxygenase. Peroxidase inactivation is commonly used in vegetable processing, since peroxidase is easily detected and is the most heat stable of these enzymes. Unfortunately the most elite industries of Pakistan engaged in the business of freezing vegetables have not developed a facility to check either the blanching was adequate or not. Then I am not to sure how they claim the quality of the frozen good. In addition to this there products are being purchased by eminent hotels and restaurants like, pearl continental, pizza Hut etc. When the blanching has not been proper then the vegetables will be subjected to spoilage and ultimately encourages the growth of many types of bacteria, most of which can cause food poisoning.
Microorganisms differ significantly in their sensitivity to freezing, thus the main concern about the microbiological aspects of freezing is the growth of organisms during thawing rather than during freezing. In general, the freezing process does not significantly destroy the microorganisms that may be present in fruits and vegetables even after blanching. The blanching process prior to freezing destroys some microorganisms and there is a gradual decline in the number of microorganisms during freezer storage. However, a sufficient number of survivors are still present that can multiply and cause spoilage of the product during thawing. If the blanching was not adequate then the spoilage due to microorganism will be more during storage and thawing. Fluctuation in storage temperature is one of the main reasons for microbial deterioration of frozen products during storage. Thus, a careful inspection of frozen products is essential to ensure proper freezing storage with constant temperatures.
The transportation of the frozen foods is also very important step. During transportation it is essential to control the temperature of the product, as required. The temperature fluctuation causes deleterious effects on the product quality. Because temperature fluctuation causes thawing and then re-freezing. This process of thawing and re-freezing cause the formation of bigger ice crystal. These bigger ice crystals enhance the spoilage and microbial growth. unfortunately most of the transportation companies carry mix loads of entirely opposite temperature requirements like carrying frozen vegetables(this require -18oC) with chocolates(this requires +4oC). In this case one can not control the thawing and Re-freezing spoilages and microbial growths. So this means that even if all process of production and storage were carried out best even then product would be deteriorated before reaching to the customer.
So if we wish to improve our industry of frozen food products we need to take some actions as early as possible. Although most of us know that the taste, flavour and aroma which vegetables of sub-continents have are not found all over the world. Then why we are having lesser share in global market than Europe and USA even though there vegetables don't have the good taste, flavour and aroma. This all is because of our poor processing techniques, non-availability of proper testing and lab equipment, improper and unstable freezing process, and unreliable transportation systems.

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