Food or edible material: processes – compositions – and products – Measuring – testing – or controlling by inanimate means
Patent
1992-09-14
1994-05-10
Yeung, George
Food or edible material: processes, compositions, and products
Measuring, testing, or controlling by inanimate means
426521, A23L 300
Patent
active
053105664
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method of ensuring constant product quality and safety when tailback conditions occur in pasteurisers, the pasteuriser being operated on a throughfeed basis in such a manner that the product passes through different temperature zones, and a configuration for implementing the method.
Pasteurisers, particularly so-called tunnel pasteurisers, are integrated in equipment such as automatically operated bottling lines. Pasteurisation preserves products such as beverages, fruit and vegetables packaged in bottles, jars or tins. This procedure involves sprinkling or spraying the packages and their closures with water at different temperatures in several temperature zones. Warm-up zones are located upstream of the pasteurising zone and cool-down zones downstream of it. In order to minimize power consumption, heat recovery takes place within product-related exchange zones. Quantities of water, each at a different temperature level, are pumped back and forth in countercurrent fashion in a closed-loop circulation system between warm-up and cool-down zones allocated to each, with the result that the pasteuriser's power consumption is limited almost entirely to its insulation losses and to the amount of added heat that the packages carry with them as they emerge from the unit as compared with their initial temperature.
Obviously any stops, whether brief or extended, that hinder the passage of the packages through the pasteuriser, particularly those caused by interruptions on the line (tailbacks), can seriously upset the complex thermal balance of such a system. Such interruptions in throughfeed continuity can also result in overpasteurisation of the product that is in the pasteurising zone at that time if no special precautions are taken to guard against overpasteurisation. In their simplest form, such precautions can consist of such measures as reducing the temperature in the pasteurising zone when a stop occurs by spraying water of a lower temperature ("emergency cooling"), the effect being to terminate the pasteurising operation for the duration of the tailback. When the pasteuriser resumes operation, the line having been re-started after elimination of the tailback condition, there is a risk that the product's remaining passage through the pasteuriser may be too short to allow it to be kept hot for an adequate length of time to satisfy the product quality and safety requirements. This is described as underpasteurisation of the product to be processed.
The diagram shown in FIG. 1 is intended to illustrate briefly the problems surrounding the pasteurising operation. The effect of pasteurisation on the product depends on two influencing variables: the temperature T to which the product is exposed, and the time t during which that temperature acts on the product. The numeric equation given below (1) shows that the number of so-called "pasteurisation units" (PE) transferred to the product is related linearly to the time of action t and exponentially to temperature T: obtained on a product such as beer by maintaining it for the duration of one minute at a temperature of 60.degree. C.
PE.sub.I is graph showing the PE pattern of a product passing through the pasteurising zone from the point of entry into the zone (a) to the point of exit from the zone (b), assuming that its passage through the zone is uninterrupted and its speed of travel can be kept constant If a tailback halts the passage of the product through the pasteurising zone and no precautions are taken to reduce the temperature of the product in the pasteurising zone, the result will be overpasteurisation, PE, which rises linearly with the tailback time t.sub.S (system of straight lines parallel to PE.sub.I).
By contrast, if the temperature is reduced to a cool-down temperature, T.sub.K, being a temperature which should not increase PE, a distributed temperature field characterised by the system of curves T.sub.o to T.sub.n-1 will result within the product in the pasteurising zone when the pasteuriser is re-started. The curve T.sub.o descr
REFERENCES:
patent: 2203141 (1940-06-01), Gruetter
patent: 4331629 (1982-05-01), Huling
patent: 4441406 (1984-04-01), Becker et al.
patent: 4727800 (1988-03-01), Richmond et al.
patent: 4841457 (1989-06-01), Clyne et al.
Otto Tuchenhagen GmbH & Co. KG
Yeung George
LandOfFree
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