Hala Irshaid Dr. Mouhamad Sabah 8\10/2013 1

Non Thermal milk processing - Food processing : in which methods other than heating are employed to effect the inactivation of pathogenic and spoilage microorganisms, as well as the stabilization of deteriorative chemical reactions. Examples include pulsed electric field, oscillating magnetic field, and high pressure technologies. 2

1- Pulsed electric field: (PEF) is largely a non-thermal process that is able microorganisms and enzymes to some degree in liquid food such as milk and fruit juice and is reported to have minimum adverse effects on the sensory attributes to inactivate of these products. -PEF is achieved by the application of short bursts of high intensity electric fields to liquid food flowing between two electrodes. A large flux of electrical current in only short bursts flows through the food materials (e.g. milk or fruit juice), which are electrical conductors due to the presence of electrical charge carrier. In order to inactivate bacteria reports the use of electric discharge through carbo Tubercle bacilli, Escherichia coli and other thermal resistant. 3

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 Pulsed electric fields (PEF) technology consists of the passage of a liquid food through a chamber with high voltage electrodes that will transfer an electric current into the food.  The intensity will depend on the electric field strength or the voltage applied between electrodes.  PEF treatment is the application of short pulses (from micro to milliseconds) of selected electric field intensity (10 – 80 kV/cm)  When an electric field is applied to the cell, a transmembrane potential across the membrane is induced, but when this potential exceeds the natural potential of the cell the expansion of existing pores or the formation of new pores in the cell membrane occurs, with an imminent increase of the cell permeability. This phenomenon is called electroporation., 5

 The use of pulsed electric fields to process food has many advantages compared with traditional pasteurization methods, such as treatment times of microseconds,  Important energy and cost savings, as well as minimal changes in food quality, such as color, flavor or nutritive value of the product. 6

- Pasteurization of milk with Pulsed Electric Fields  Some microorganisms are successfully inactivated in milk using electric field strengths Some of these microorganisms in milk and other dairy products, represent pathogenic, surrogate and deteriorative organisms present in milk. Escherichia coli, Salmonella dublin, Lactobacillus brevis, Bacillus subtilis, Staphylococcus aureus).  The factors that can affect the degree of inactivation by PEF related to the microorganism, which can be called biological factors, are: a) Gendre b) Species c) Size d) Shape e) Growth stage.  Other factors to influencing inactivation are the intrinsic resistance of the microorganism.l 7

Some advantages that PEF offers to conventional treatments of pasteurization of milk are: a) Sensorial and nutritional properties are not or minimally degraded during the process, showing fresh-like characteristics. b) It is a safe process because no dangerous chemical reactions have been detected. c) PEF requires minimal energy and has greater energy efficiency compared tothermal treatments (PEF requires 90% less than HTST). d) PEF processing costs less than HT. E)The shelf-life of the products can be extended considerably compared to HTST. 8

(2) Electronic pasteurization, a food processing technology involving the use of ionizing radiation to destroy microbial pathogens, is a feasible solution to prevent foodborne illness and enhance global competitiveness.. Electronic pasteurization involves the use of ionizing radiation (electrons) to destroy pests and pathogens from food and agricultural products. Food irradiation can be accomplished using either radioactive isotopes or using accelerated electrons (electron beam. Ionizing radiation is defined as radiation that has enough energy to remove electrons from atoms, thereby leading to the formation of ions. 9

Ionizing radiation can occur naturally from radioactive isotopes or from artificially created isotopes using nuclear reactors and linear accelerators. There are different types of ionizing radiation such as X-rays, gamma rays, and beta rays, depending on the source. by essentially the same process: the radiation causing “breaks” in the DNA orRNA double helix. It is believed that ionizing radiations disrupt normal cellular activity by damaging the nucleic acids by “direct” and/or “indirect” effects. Specifically, single- or double-stranded breaks occur on the DNA or RNA. Ionizing radiation does not discriminate between pathogens and nonpathogens, and so both the indigenous normal flora and pathogens on a food product can be inactivated. 10

(3)High Pressure Processing High pressure processing uses pressures of 100 to 800 MPa to treat solid and liquid foods and provide a microbiologically safe and nutritionally high quality product. The efficacy of HPP depends on a series of factors such as pH, temperature, time, antimicrobial agents, and water activity. A typical HPP unit is composed of a high pressure vessel and its closure, a pressure generation system, a temperature sensing device, and a material handling system, along with a pressure transmitting medium. 11

High Pressure Processing 12

However, different foods react to high pressure in different ways, resulting in various quality deviations, and thus their composition must be taken under consideration and evaluated before selecting HPP as a process Overall, HPP offers a number of advantages compared to other non-thermal and thermal processes. These include reduced processing times, minimal heating, freshness, flavor, texture, and color quality retention. In addition, there is insignificant vitamin C loss. There have been extensive studies on the capabilities of HPP in destroying pathogens and maintaining food quality by denaturing certain enzymes. It has been shown that HPP can eliminate vegetative bacteria more effectively than spores and has a 4 higher success rate in destroying bacterial cells in the growth phase when compared to cells in the stationary phase. In general, Gram-negative microorganisms are more pressure sensitive than Gram-positive microorganisms. 13

The primary aim of treating foods with High Pressure Processing (HPP) is to reduce or eliminate the relevant foodborne microorganisms. It can cause the fat globule thinning while homogenating under the high pressure to the milk, soy milk this kind of dairy food, And cause its products to be easy to digest and absorb, and to improve the dietary value. 14

High Pressure Milk Processing (Heat Vs Pressure) Heat-pasteurization will kill the microbes and keep the milk fresh and safe. Using high pressure at low temperature can also preserve the milk. In fact this high pressure treatment can account for much fresher and safe milk than the conventionally heat- pasteurized milk. Advantages of HPP over the combined thermal and pressure treatments is that this HPP processed milk/dairy products will be processed at low temperature and heat- damage can be prevented. Heat is responsible for change in chemical properties. 15

So, if heat is applied then there is a chance of alteration in chemical bonds which in turn affects the flavor of milk.  Many cases like cooked flavor, roasted flavor are observed when high-temperature processing is followed. Heat destroys the vitamins. One of the important constituents in diet will not be available in milk. Let us now discuss about the time taken to process the food. Heat processing takes more time to process food than pressure processing. More over, the shelf-life of ultra-high temperature milk was about half of the shelf-life 1\6 of high-pressure processed milk shelf life can added. 16

As the shelf-life is longer, the milk will not get spoiled within the short span of transport and lasts for longer time. How many months can we preserve the milk??? Depending upon the amount of pressure applied, time exposed to high pressure, different flavors of milk can be preserved from 4 months to 36 months. 17

What else one can achieve through HPP??? → HPP is applied only in few countries؟؟. This technology can be extended to all countries thus preserving the milk in different flavors for a longer period of time. → Different flavors of milk used now for preservation through HPP are chocolate flavor milk, low-fat milk, mango flavored milk etc., This technology can be applied for developing and preserving new flavored milk drinks. 18

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