Quality • Food quality is
a sensory property that includes appearance, taste, nutritional value (nutrient content), health benefit (functional ingredient) or safety (chemical, physical, biological). • It includes those attributes which affect consumer‟s choice for a product.
Need For Quality Food •Major
challenge for food industry is to maintain the food quality ; the reason being well aware consumers. •For this reason food industry has to adopt certain techniques in order to meet the growing need of maintaining food quality; this is known as food quality control. •The main issue which is considered while quality control process is to deteriorate the level of microbes and other contaminants in food.
What is Ultrasound? • It
is a form of energy generated by sound waves of frequencies that are too high to be detected by human ear, i.e. above 16 kHz. •Ultrasound can propagate in gases, liquids and solids. •Considered to be technologies that were developed to minimize processing and maximize quality and safety in food •These applications include improvement in microbial inactivation, food preservation, manipulation of food texture and food analysis.
Physics of Ultrasound • The
sound waves travel effectively through liquids which are comprised of closely compacted molecules • Sound is transmitted as sequential sine waves whose height represents amplitude or loudness. • A single full cycle is measured from peak to peak, and the number of these cycles per one second represents the frequency. The frequency is described in Hertz [Hz] which by convention is in honor of the German physicist Heinrich Hertz for his work on electromagnetic transmission.
How can Ultrasound be applied
in Food ? • Ultrasound when propagated through a biological structure induces compressions and depressions of the particles and a high amount of energy is imparted. In food industry, the application of ultrasound can be divided based on range of frequency: low power ultrasound high power ultrasound
Low Power Ultrasound: • Low
energy [low power, low intensity] ultrasound Principles of LPU for Food Analysis: • It uses a small power level that the waves cause no physical and chemical alteration in the properties of the material through which it passes. • This property is been utilized for non-invasive analysis and monitoring of various food materials during processing and storage to ensure quality and safety. • Ultrasonic velocity (v) is determined by density (ρ) and elasticity (E) of the medium, according to the Newton-Laplace equation (Blitz, 1963).
Newton-Laplace Equation: •The Newton-Laplace equation
is the starting point for the determination of isentropic properties of solution, using the speed of sound u and density (ρ). •This equation implies that the ultrasound velocity of the solid form of a material is larger than that of its liquid form. •In food industry, the sensitivity of ultrasound velocity to molecular organizations and intermolecular interactions makes UVM – Ultrasound Velocity Measurements suitable for determining composition, structure, and physical state of different food materials. •It also helps in detection of foreign bodies and defects in processed and packaged food.
Why Low Power ? •
Can provide information about the physiochemical properties of food materials, their composition, structure and physical state. • The major advantage of this technique over other traditional techniques is that the measurement is so rapid and non-destructive.
High Power Ultrasound: • High
energy [high power, high intensity] ultrasound • 20 and 500 kHz • Disruptive and enforce effect on the physical, mechanical, or biochemical properties of foods. These effects are promising in food processing, preservation and safety.
The chemical and biochemical effects
are effective tools for sterilizing equipments, preventing contamination of food processing surfaces by pathogenic bacteria and removal of bacterial biofilms. Principle of HPU Factors that affect power ultrasound are energy, intensity, pressure, velocity and temperature. Where, Pa is the acoustic pressure (a sinusoidal wave), which is dependent on time (t), frequency (f) and the maximum pressure amplitude of the wave. Pa max is related to the power input or intensity (I) of the transducer: I = Pa max/ 2ρv , where ρ is the density of the medium and v is the sound velocity in the medium. Mechanical Chemical and Biological Effects:
Why HPU ? Ultrasonic Inactivation
of Microorganism • The most common techniques currently used to inactivate microorganisms in food products are conventional thermal pasteurization and sterilization. • Thermal processing does kill vegetative microorganisms and some spores; however, its effectiveness is dependent on the treatment temperature and time. • The magnitude of treatment, time and process temperature is also proportional to the amount of nutrient loss, development of undesirable flavors and deterioration of functional properties of food products.
• High power ultrasound is
known to damage or disrupt biological cell walls which will result in the destruction of living cells. • Unfortunately very high intensities are needed if ultrasound alone is to be used for permanent sterilization. However, the use of ultrasound coupled with other decontamination techniques, such as pressure, heat or extremes of pH is highly applicable. Thermosonic (heat plus sonication), manosonic (pressure plus sonication), and manothermosonic (heat plus pressure plus sonication) treatments are likely the best methods to inactivate microbes, as they are more energy – efficient and effective in killing microorganisms.
The advantages of ultrasound
over heat pasteurizationinclude: Minimizing of flavor loss, greater homogeneity and significant energy savings. The effectiveness of an ultrasound treatment is dependent on the type of bacteria being tested, amplitude of the ultrasonic waves, exposure time, volume of food being processed, the composition of food and the treatment temperature.
Ultrasound in Food Industry •
Major Significance to Industry and Consumers • Better quality and Healthy Food • High Efficiency • Saves Energy and Costs
Process involved • packaged food
is passed through a radiation chamber on a conveyor belt • It is passed through a radiation beam, like a large flashlight, instead of coming in direct contact with the radioactive materials
How does Food Irradiation Works?
• Food is exposed to a carefully measured amount of intense ionizing radiation. • When food is irradiated, the radiation energy breaks the bonds in the DNA molecules of microorganism. Thus, the organism dies or becomes unable to reproduce. • Frozen foods take larger radiation dose to kill microbes. • The effectiveness of the process depends on the organism‟s sensitivity to irradiation.
• The food irradiation process
uses three types of ionizing radiation sources: cobalt-60 gamma sources : most commonly used as they can deeply penetrate into food electron beam generators x-ray accelerators gamma rays
Dose Effects • Absorbed dose
is measured as the quantity of radiation imparted per unit of mass of a specified material. • The unit of absorbed dose is the gray (Gy) where 1 gray is equivalent to 1 joule per kilogram. • Low doses (up to 1 kGy) inhibit sprouting in tuber, bulb and root vegetables, inhibit the growth of asparagus and mushrooms, and delay physiological processes (ripening, etc.) in fruits • Medium doses (1 to 10 kGy) extend the shelf life, eliminate spoilage and pathogenic microorganisms • High doses (10 to 50 kGy) can be used for industrial sterilization and decontamination of certain additives or ingredients
• Parasites and insect pests,
which have large amounts of DNA, are rapidly killed by an extremely low dose of irradiation. • It takes more irradiation to kill bacteria, because they have less DNA. • Viruses are the smallest pathogens that have nucleic acid, and they are, in general, resistant to irradiation at doses approved for foods. • Another useful effect: it can be used to prolong the shelf life of fruits and vegetables because it inhibits sprouting and delays ripening.
IMPACT !! It has been
studied that when irradiation is used as approved on foods: • Disease-causing microorganisms are reduced or eliminated • The nutritional value is essentially unchanged • The food does not become radioactive • Irradiation is a safe and effective technology that can prevent many food borne diseases.
Considering its potential role
in the reduction of post-harvest losses, providing safe supply of food and overcoming quarantine barriers, food irradiation has received wider government approvals during the last decade. There is also a trend towards increased commercialization of irradiated food. Currently, there are 47 irradiation facilities in some 23 countries being used for treating foods for commercial purposes. Current Scenario
Advantages • kill many insects
and pests that infest foods like grains, herbs and spices without appearing to affect them • kill or considerably reduce the level of dangerous micro organisms in foods such as salmonella and campylobacter in raw meat and poultry. • Listeria in ready to eat foods like hot dogs • Delay or stop normal ripening and decay processes so that foods can be stored for longer • Irradiation can successfully replace the fumigation treatment of cocoa beans and coffee beans and disinfest dried fish, dates, dried fruits, etc.
• One of the most
important advantages of food irradiation processing is that it is a cold process which does not significantly alter physico-chemical characters of the treated product. • It can be applied to food after its final packaging
Are irradiated foods still nutritious?
• Their nutritional value doesn’t change • levels of the Vitamin - Thiamine are slightly reduced, but not enough to result in vitamin deficiency. • no significant changes in the amino acid, fatty acid, or vitamin content of food. • the changes induced by irradiation are so minimal that it is not easy to determine whether or not a food has been irradiated. • A big advantage of irradiated food, is that it is a cold process: the food is still essentially “raw”, because it hasn‟t undergone any thermal process.
Disadvantages • Is used on
a very limited range of foods as it is an expensive technology • Affects some important constituents of foods, for example, vitamin E levels can be reduced by 25% after irradiation and vitamin C by 5-10% • Radiation doses at the levels recommended will not kill all micro organisms, 90% may be destroyed so need to handle with care otherwise remaining organisms can reproduce rapidly • Ineffective against viruses - as they are the smallest pathogens that have DNA or RNA, and they are relatively resistant to irradiation at the levels approved for foods.
• Prions, such as the
one that causes “mad cow” disease (bovine spongiform encephalopathy, or BSE), have no DNA, so they also are not affected by irradiation at the levels approved for foods. • Can create new substances called Radiolytic products. While this does not mean that the food is radioactive, there is considerable controversy over whether these products are unique and if so whether they are dangerous.
Current Scenario • Preferences of
the consumers have shifted towards healthy, tasty foods, which are readily available, ready to eat and easily stored • Challenge to Food Industries – providing such foods in a form suitable for distribution and mass production without affecting texture, flavour, and color, is technically complex and expensive.
What is Cold Plasma Technology
? • Cold Plasma Technology is a novel, non thermal food processing technology that uses energetic and reactive gases to inactivate contaminating microbes in food products ( E.g.. meat, poultry, etc.,) • Plasma is a mixture of positive and negative charges as well as neutral particles and photon. Plasma exist over a massive range in temperatures and densities. • It is estimated that 99% of the known universe is in a plasma state. The sun and stars are examples of natural plasmas
Generation of Plasma • Man-made
plasma can be generated at low temperatures typically by applying a voltage to a gas. The electric field generated from the applied voltage can accelerate any free electrons in the gas. • Accelerated electrons collide with gas atoms to excite or ionise them. Ionisation of gas atoms releases more electrons; this cascaded reaction can generate a rich abundance of highly reactive chemical species which are capable of inactivating a wide range of microorganisms including food borne pathogens and spoilage organisms.
Cold Plasma Technology in Foods
• Cold Plasma Technology in food Industry relies on gas discharge technology - an effective, economical, environmentally safe method for critical cleaning. • The vacuum ultraviolet (VUV) energy is very effective in the breaking most organic bonds (i.e., C-H, C-C, C=C, C-O, and C-N) of surface contaminants. This helps to break apart high molecular weight contaminants.
• A second cleaning action
is carried out by the oxygen species created in the plasma (O2+, O2-, O3, O, O+, O-, ionised ozone, excited oxygen, and free electrons). • These species react with organic contaminants to form H2O, CO, CO2, and lower molecular weight hydrocarbons. • The resulting surface is ultra-clean/sterilised. The plasma activated atoms and ions cause molecular „sandblasting‟ and can break down organic contaminants.
Cold plasma can be used
for decontamination of products where micro-organisms are externally located. Unlike light ( UV decontamination), plasma flows around objects, which means „Shadows Effects‟ do not occur ensuring all parts of a product are treated. For products such as cut vegetables and fresh meat, there is no mild surface decontamination technology available currently, cold plasma could be used for this purpose. Can also be used to disinfect surfaces before packaging or included as packaging process
• Illustration – Sterilization capability
of Cold plasma • E.coli – inoculated in to 3 Petri dishes. • One dish was left as a control with no plasma exposure, another was exposed for 30s of plasma treatment, and a third was exposed for 120 seconds. • The bacterial kill zone was progressively higher with longer plasma exposure
• Common pathogen – Unprocessed
meat – 70% Salmonella • Plasma Torch - Applied for 180s, • Plasma eliminated or subsequently reduced low levels of bacteria from both skinless chicken and chicken skin itself.
• Plasma is used as
a method for killing Salmonella on egg shells. • Askild Holck, senior research scientist at Nofima: “By using plasma treatment, we have succeeded in removing 99.5 per cent of all bacteria on the egg shell but because this is a gentle method, the egg yolk and white are unaffected." Bacteria‐free eggs with plasma technology.
Concerns !! • Important aspects
of this technology are still immature, particularly with respect to its use with food nutrition • We do not know how cold plasma inactivates spores or how the cold plasma – specifically the electronically excited molecules – interact with the food or packaging materials, or the stability of the plasma for large-scale commercial operation. • Need to determine optimum operating conditions for a given application - Safety of treated products.
References T.J. Mason, L.
Paniwnyk, J.P. Lorimer. Ultrasonics Sonochemistry 3 (1996), The uses of ultrasound in food technology, Pages S253-S260 Retrieved from http://www.vscht.cz/ktk/www_324/studium/konzervace/pdf/ultrazvuk.pdf Hao Feng, Gustavo V.Barbosa-Canovas, Jochen Weiss. Ultrasound technologies for Food and Bioprocessing. Food engineering series, pages 1-10 Retrieved from http://books.google.ca/books?id=jHRczaYL18C&printsec=frontcover&source=gbs_ge_sum mary_r&cad=0#v=onepage&q&f=false Erika Kress-Rogers and Christopher J.B. Brimelow, Woodhead publishing in food science and technology, Instrumentation and sensors for the food industry-second edition. Pages 361-390 Zbigniew J. Dolatowski, Joanna Stadnik, Dariusz Stasiak ,Application of ultrasound in food technology, Acta Sci. Pol., Technol. Aliment. 6(3) 2007, 89-99