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As the days, months, years passes by food safety still remains as a serious question among producers and consumers. Extrusion is a processing technique which involves forcing material through a die. Widely applied in the food industry for shaping and texture, particularly with a view to modify the sensory properties (Properties that can be detected by the sensory organs. For foods, the term relates to the combination of concepts such as visual aesthetics, flavor, texture, astringency (the reaction infants give to sour taste) and aroma or smell of the resultant extruded foods. Foodborne illnesses are a major threat all around the world. Among every 6 people die due to food diseases. Since a long ago these diseases were traced in association with high-moisture food, however nowadays low-moisture food has also been hinted as a con. Low-moisture food cannot be framed as safe due to the absence of salmonella. Even a presence of one cell of salmonella in food at any level poses threat to its consumer. Due to increased number of breakouts arising from salmonella in low-moisture food, it is necessary to develop and validate a process which could assure to control the microbiological safety of the end products.
Extrusion is one of the most common processes used in industries. Defined as a process in which material is pushed through an orifice or a die of a given shape, the pushing force is applied using a piston or a screw; in food application, screw extrusion is predominant (Karwe, 1992).
It is a founding pillar to adding value to agriculture and is known to bring more to the industry. It is known to use several unit operations which contains kneading, mixing, cooking, shearing, forming and shaping. The HTST (high temperature short time) has been known since long to reduce enzymatic activities, microbial population and reduces anti-nutrition factors, resulting in products that are low in water activity and reduces salmonella in high-moisture food at a temperature above 85 degrees Celsius. The requirements contain certain variables that are as follows; feed humidity, feed constituents, input size and shape, vessel temperature, rotation of screws, die dimensions and the configuration of the setup. There are many studies related to high-moisture food, but when it comes to low-moisture food, there are fewer studies. When it comes to validation an adequate surrogate becomes necessary for inactivation of pathogens. An adequate surrogate is must while assisting large scale validation study for low-moisture food.
Low-moisture food has been considered safe till date and was not the talk of town in terms of food safety as they dont possess an environment that could shelter diseases. Low-moisture food contains some types of food that do not require cooking for consumption like-dry fruits and some type of food that are ready to eat. But the real question is whether the low-moisture food is safe? In past few years, the combination of low-moisture foods with pathogens has attracted the attention of the scientific community and regulations. Based on all the information present regarding Salmonella and low-moisture foods, it becomes clear need for an industry to validate processing areas so as to ensure the safety of foods and consumers.
The need of consumers increases with advancement in knowledge of microbiology and revelations about microbiological pathogens and hence the requirement of microbiological safety of food products. Many of the common foods such as chips, fries, nuggets, and most breakfast cereals are generally recognized as safe to consume as the condiments are exposed to high temperature treatment (>130 degree Celsius), the water activity is also low, that is 0.1-0.4. And so was proven that many yeasts and molds are terminated under simple processing.
The food industry is always inventing solutions and new process methods to resolve upcoming issues. There are various units in an industry to ensure the safety of the food among which is an exclusive unit of extrusion. Extrusion is every charmed process in food and feed industry; its a process that combines cooking, mixing, kneading, forming and shaping. The sole purpose of extrusion is to cook, to change or to create texture, to reduce microbial hazards and to inactivate bacteria. There exist various types of extrusion such as cold, hot or thermal extrusions. With the new insights studies could be conducted in support of extrusion related methods to reduce the threats present in low as well as high moisture food.
Salmonella is the name of a generic bacteria isolated by Dr. A. E. Salmon in the year 1885. It is a rod-shaped bacterium, which is gram-negative in nature. They are generally present on nearly all raw foods, including eggs, oilseeds, and sausages etc. It induces an illness called salmonellosis.
There are some 11 commonly recognized factors that determine the death of microorganisms and their death. They are as follows pH levels, phase of growth in organisms, nitrogen content, carbohydrates, salts, lipids, water activity, size of colony, inhibitory compounds, heat, and time. The Thermal Death Time (TDT) is the most significant procedure while extrusion and is necessary for the reduction of Salmonella and some other microorganisms. TDT is defined as the time necessary to kill a given number of organisms at a specified temperature . Furthermore, death is defined as the inability of the organisms to form a visible colony .
A handful of studies have been ever conducted to evaluate the effect of extrusion on Salmonella sp. or on similar organisms, a study depicted that when high moisture foods were extruded it completely eradicated Salmonella provided the temperatures were 93.3 to 176.8 degree Celsius , and the moisture content was no more than 35% and also not less than 25%.
As a conclusion we can see that the possibilities of Salmonella to relapse is still present by a small percentage, therefore it is safe to say that quite a lot of research is needed into this specific topic, and also it is necessary to get rid of Salmonella from food products so we may enjoy a safe life. Also, a part of information to be kept in mind that Salmonella sp. are very adaptive in nature and can adapt to the chemicals and heat treatment provided to exterminate them, hence we should always be cautious while conducting sanitary practices and ensure that machinery is also sanitized. These healthy practices lead to lesser chances of bacterial infection/contamination.
References
- Jideani, Afam. (2014). Extrusion Bolsters Food Security in Africa.
- IJISET – International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 4, April 2015.
- Journal of Food Protection, Vol. 75, No. 9, 2012, Pages 16461653
- IFT Report to FDA – 2000, Vol. 2, 2003 COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY.
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