Food or edible material: processes – compositions – and products – Processes – Heating above ambient temperature
Reexamination Certificate
2000-07-10
2002-06-25
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Heating above ambient temperature
C426S665000
Reexamination Certificate
active
06410071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method and control system for controlling pasteurization of food products.
2. Background
In food products, heating can bring both benefits and detriments to the products. For example, heating can pasteurize, tenderize and/or cook food products. Too much or too poorly controlled heating, on the other hand, can impair the functionality of and, e.g., cook or significantly alter the flavor profiles of food products that are supposed to be uncooked (i.e., that are supposed to substantially retain the useful properties of the uncooked product), or, e.g., toughen, burn, dessicate or significantly alter the flavor profiles of cooked food products.
Pasteurizing of proteinaceous food product can be carried out by heating to destroy infectious organisms such as salmonella. Pasteurization may be defined as heat treatment for the purpose of killing or inactivating disease-causing organisms. For example for milk, a minimum exposure for pasteurization is 62° C. for 30 minutes or 72° C. for 15 seconds. The latter exposure is called flash pasteurization. Complete sterilization may require ultra-high pasteurization such as treatment at 94° C. for 3 seconds to 150° C. for 1 second to kill pathogenic bacteria and inactivate enzymes that cause deterioration and to provide for satisfactory storage life.
Minimum food safety processing standards for various commodities have been promulgated and are enforced by the United States Department of Agriculture (USDA). Pasteurization may be defined in accord with the standards mandated by the USDA. The Nutrition Action Health Letter published by the Center For Science In The Public Interest (July/August 1991 Edition, Vol. 18, No. 6, “Name Your (Food) Poison”) describes concern with the growing number of cases of food poisoning due to food infections.
Many known processes for pasteurizing food are insufficient to assure safety of some foods from infections or cannot be applied to some food products. The “Name Your (Food) Poison” article reports that dairy products, eggs, poultry, red meat and seafood, in that order, are the most common causes of food poisoning. Shell eggs are particularly difficult to pasteurize because of their structure. The article indicates that one of 10,000 eggs is contaminated with salmonella enteritis.
The United States Department of Agriculture (USDA) regulates minimum safety standards for pasteurizing in-shell eggs. These standards are promulgated in order to ensure that certain microorganisms, including such infectious organisms as Salmonella, are substantially destroyed prior to distribution and consumption of the eggs. The USDA defines pasteurization as a heat treatment for the purpose of killing these disease-causing organisms.
One source of infection arises when the egg shells come into contact with organic refuse. Contamination results because the egg shells have numerous pores which permit infectious microbes, which are contained in the organic refuse, to penetrate the pores of the eggs. Another source of infection results from trans-ovarian contamination. This occurs when chickens or other poultry ingest or are otherwise infected by infectious microbes and transfer the microorganisms directly into the eggs.
Techniques for improving pasteurization of eggs have been proposed. These techniques attempt to destroy infectious disease causing organisms in in-shell eggs without substantial loss of functionality. One approach to pasteurizing in-shell eggs involves heating the in-shell eggs in water baths, for various times and at various temperatures. The time/temperature ratios vary widely because different approaches involve a compromise between the degree of safety achieved and the quality or the functionality of the eggs retained after pasteurization is completed. The USDA has devised time/temperature ratios, but they are only for liquid eggs.
Cox et al. (PCT/US94/12950), which is hereby incorporated by reference, discloses a method for destroying infectious disease causing organisms in in-shell eggs without substantial loss of functionality. Cox et al. employs a temperature versus time relationship in order to accomplish pasteurization of the in-shell eggs. An initial egg temperature and processing temperature at the beginning of the pasteurizing process of a whole shell egg must be known. These temperatures are used to determine the total processing time, e.g., the total length of time over which the eggs are heated. According to a preferred embodiment of Cox et al., minimum temperatures/time requirements for liquid whole eggs are applied equivalently to in-shell eggs once the selected pasteurization temperature has been achieved at the shell egg yolk center.
Cox et al. uses the following temperature timetable for determining the pasteurization time of in-shell eggs.
Temperature
Real Processing Time (RPT) (Minutes)
130° F.
=65
131° F.
=49
132° F.
=38
133° F.
=28
134° F.
=20
135° F.
=16
136° F.
=11
137° F.
=8
138° F.
=6
139° F.
=4.75
140° F.
=3.5
This table describes the processing of in-shell eggs after they attain the required pasteurizing preprocessing temperature. The initial temperature is applied until the in-shell eggs reach a temperature equilibrium with the heat transfer medium. The RPT for a given pasteurization regimen can only begin after this point has been reached.
Cox et al. also discloses that factors including the size and internal initial temperature of the eggs may affect the time required for the eggs to reach the effective processing temperature. Thus, an initial temperature that causes pasteurization of one batch of eggs may result in impaired functionality of a second batch of eggs having a smaller size, depending on the variables associated with that particular batch of eggs.
Davidson International Application No. PCTI/US96/13006 (U.S. application Ser. No. 08/519,184), also discloses methods to pasteurize in-shell eggs using time/temperature relationships. In particular, Davidson discloses heating a yolk of the egg to within the range of 128° F. to 138.5° F. Once the yolk reaches this temperature range, it must be maintained at this temperature range for a certain time and within certain parameters.
FIG. 1
shows a temperature versus time curve implemented by the Davidson system. This curve is based substantially on the data of the above table. Referring to
FIG. 1
, the temperature of the egg yolk must be maintained between parameter line A and parameter line B in order for sufficient pasteurization to occur. According to Davidson, this will reduce the Salmonella by at least 5 logs, while at the same time retaining the functionality of the eggs. If the eggs are heated to a limit outside parameter lines A and B, however, the eggs will either lose their functionality or remain insufficiently pasteurized. Thus, according to Davidson it is imperative that the temperature of this system should stay within the predefined parameters.
Factors such as loss of water, temperature overshoot (e.g., raising the temperature too high), inefficient temperature sensors (e.g., low response time for raising the temperature to a predefined temperature range), and numerous other factors make it possible for the bath temperature to stray from preferred parameters. The size of the eggs, the number of eggs placed in the bath and the initial internal temperature of the eggs will also affect the pasteurization time and functionality of the eggs.
Whole eggs are not the only food products that are subject to bacterial or other such contamination. For example, other uncooked proteinaceous food products such as uncooked meat (e.g., beef, veal, pork, mutton, lamb or poultry), fin fish and shellfish (e.g., oysters, clams, scallops, mussels, crabs) are all too often contaminated with bacteria such as
E. coli
and others. The contamination may occur in nature or during processing. An especially common source of contamination exists in processin
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