Food sterilisation

In some applications, particularly in the nuclear industry, medical instrumentation and food sterilisation, plastics are subjected to damage, which is associated with a loss in molecular weight and deterioration of some physical properties, such as impact strength and colour change upon exposed the plastics to gamma rays [65, 66]. 

The mechanical, electrical and thermal properties of polymers are discussed as are other diverse applications such as solvent and detergent resistance, frictional and hardness properties, food packaging applications and gas barrier properties. In addition a very important application is discussed of the resistance of plastics to gamma and other forms of radiation namely their use in nuclear industry, medical applications and food sterilisation. 

Manmade sources of radiation include industry (mining, food sterilisation, radiography of pipes, luggage and buildings), medicine (imaging, radiotherapy), nuclear power and weaponry. Weak radiation sources are also found in smoke detectors. 

It is worthwhile drawing attention to health hazards associated with film infected water systems which also cause corrosion. Two of the most common are Legionnaires disease and so called humidifier fever . Because of strong adhesion of biofilms and diffusion rates through the film treatment based on cleaners and chemical sterilisers such as chlorine often fail similar considerations apply to other systems in industry, e.g. food, paint, oil and gas are examples where biofilm activities have given massive problems. 

Both fungi will grow at pH 2.5, at which non-aseptic processes can be operated (that is without sterilisation). However, the SCP grown in non-aseptic systems is suitable only as feed. The SCP from both organisms can be used as a high-protein food additive, but Fusarium sp. must be ground up (powdered) for this. In addition, the filamentous fungus can be used to make meat substitutes. For this the SCP must be prepared deep-frozen and not dried. 

To produce Candida sp. as food additive the above process could be operated, except that fermentation would have to be aseptic (with sterilisation costs). The cost would be 0.647 + 0.04 = 0,687 per kg biomass or 1.145 per kg protein. 

Commercial sterilisation is a more severe process than pasteurisation as the temperature is higher (70-90°C). The process is used to protect food during long-term storage. The oxygen residue should be minimised before heating to reduce deterioration of antioxidants or, in some cases, antioxidants... 

Garrison, W.M. (1981). The radiation chemistry of amino acids, peptides and proteins in relation to the radiation sterilisation of high-protein foods. Radiat. Effects 54, 29-40. 

This gum was the first microbial gum to be used in the food industry. It is produced by the aerobic fermentation of Xanthomonas campestris. A specially selected culture is grown on a carbohydrate-containing nutrient medium with a nitrogen source and other essential elements. The pH, temperature and aeration are controlled carefully. The product is then sterilised and the gum is precipitated with propan-2-ol. Next, the precipitate is washed, then pressed to remove residual alcohol, followed by drying and grinding to the required size. 

The stimuli used as odours in this study were almond food flavouring (Supercook, Leeds, England) cKl unisex perfume (PVH Corp., New York, USA) and distilled water. The odours were introduced into the gorillas environment on sterilised white flannel towels (100% natural cotton, 450 gsm, 70 cm x 140 cm). 

Polypropylene is used in sterilisable medical and chemical equipment machine parts, food packs, book coverings, packing meat and cheese, washable wall paper yarn to make socking, etc. 

Because flexible films have excellent strength and good electrical and thermal properties, have low permeability to gases, water, oil, odour and could be sterilised so they are used in capacitors, cables, magnetic recording tapes, typewriter ribbons, food packaging, tracing film, book covers, etc. The film is coated with aluminium by vacuum disposition and used for decoration and in textiles. 

M. Lewis and N. Heppell, Continuous Thermal Processing of Foods — Pasteurisation and UHT Sterilisation, Aspen Publishers, New York, 2000. 

The direct sterilisation of particulafe solid foods in a gas-solid fluidized bed was proposed as long ago as 1968 by Lawrence et al. (1968) who sterilised wheat flour in steam-air mixtures at the pilot scale. However, Jowitt (1977) described an atmospheric pressure process for fhe sferilisation of canned foods in which the cans are immersed in a fluidized bed of inert particles. This has a number of advantages compared to the conventional retorting process using pressurised steam or hot water ... 

However, this does not necessarily apply to foods which heat by convection. Jowitt quotes both peas in brine and soup as examples where the process time was doubled in a fluidized bed (22 minutes) compared to a steam-heated retort (11 minutes) for the same total process lethality. However, increasing the fluidized bed temperature by 8K resulted in almost equal process times and approximately equal retention of the heat-sensitive vitamin thiamine. Following the heating and holding stages of the sterilisation operation, the cans were cooled in a fluidized bed in which heat was removed by cooling water passed through finned tubes immersed in the bed (Jowitt and Thorne, 1971). 

Aseptic processing is used to achieve commercial sterility in a continuous flow of liquid or semi-liquid food by heating the food to a suitable temperature before placing it in previously sterilised packaging. The sterilisation of liquids containing particulates presents a number of... 

Following the favourable response of this committee, steps were taken to amend the existing UK legislation which permitted only the radiation sterilisation of foods for people whose immune response was compromised. New regulations came into force in early 1991 which permitted the irradiation of seven groups of foods under strictly controlled conditions (Anon., 1990a) (Table 1). 

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