IGEM:IMPERIAL/2007/Projects/Cell by date/Design: Difference between revisions
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===Phase 1 : Mimicking Printed Sell By Date=== | ===Phase 1 : Mimicking Printed Sell By Date=== | ||
This first level of complexity hopes to calibrate our system so that it will mimic the function of the Sell By Date printed on the meat packets found in supermarkets, eg. '''Sell By 12/06/07''' | This first level of complexity hopes to calibrate our system so that it will mimic the function of the Sell By Date printed on the meat packets found in supermarkets, eg. '''Sell By 12/06/07''' | ||
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The food industry calculates these Sell By Dates by using a technique called '''Challenge Testing'''. The Meat we purchase in our local supermarkets was once an animal that was slaughtered, processed and packaged before we pick it up off the shelf at ASDA or Tesco. When the meat is packaged it is already contaminated with bacteria. Over time these bacteria feed off the meat ,multiply and grow : we precieve this as discoloration or mould formation on our food. After time the bacteria and grown so much that the food is no longer good to eat, when this happens the food is called '''spoilt''' or '''off'''. | The food industry calculates these Sell By Dates by using a technique called '''Challenge Testing'''. The Meat we purchase in our local supermarkets was once an animal that was slaughtered, processed and packaged before we pick it up off the shelf at ASDA or Tesco. When the meat is packaged it is already contaminated with bacteria. Over time these bacteria feed off the meat ,multiply and grow : we precieve this as discoloration or mould formation on our food. After time the bacteria and grown so much that the food is no longer good to eat, when this happens the food is called '''spoilt''' or '''off'''. | ||
The time taken for the meat to go off depends upon the environment the meat is placed in, bacteria will grow quicker in higher temperatures for example and so will go off quicker in higher temperatures. The Sell By Date printed on our meat packets is calculated on the assumption that the meat will be exposed to certain conditions, for example that meat will always be refrigerated at 10<sup> | The time taken for the meat to go off depends upon the environment the meat is placed in, bacteria will grow quicker in higher temperatures for example and so will go off quicker in higher temperatures. The Sell By Date printed on our meat packets is calculated on the assumption that the meat will be exposed to certain conditions, for example that meat will always be refrigerated at 10<sup>o</sup>C from the time it leaves the processing factory to when we pick it up at the supermarket. This chain of refrigeration is know as the '''Cold Chain.''' | ||
The Cold Chain of the Food Industry is highly regulated and developed but what happens after we pick it up from the Supermarket Shelf? The Food industry has addressed this problem using their '''Challenge Testing''' technique, which involves conservative estimates of when food will spoil as to avoid people eating off meat. This means that often the printed cell by date insinuates meat is off when in fact it isn't. | The Cold Chain of the Food Industry is highly regulated and developed but what happens after we pick it up from the Supermarket Shelf? The Food industry has addressed this problem using their '''Challenge Testing''' technique, which involves conservative estimates of when food will spoil as to avoid people eating off meat. This means that often the printed cell by date insinuates meat is off when in fact it isn't. | ||
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===Phase 2 : Minced Beef Specific Temperature Exposure Device=== | ===Phase 2 : Minced Beef Specific Temperature Exposure Device=== | ||
==== 2A : Gradient ==== | ==== 2A : Gradient ==== | ||
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===Phase 3 : General Meat Heat Exposure Device / Abstraction for re-usability=== | ===Phase 3 : General Meat Heat Exposure Device / Abstraction for re-usability=== | ||
More info to be added! | More info to be added! | ||
Revision as of 09:07, 31 July 2007
Cell by Date: Design
Summary
The Cell By Date Project has three levels of complexity and we hope to implement these levels in three seperatre chassis: E.coli, in-vitro and in-veso. These chassis are being characterised as one of ICGEMs sub-projets.
Phase 1 : Mimicking Printed Sell By Date
This first level of complexity hopes to calibrate our system so that it will mimic the function of the Sell By Date printed on the meat packets found in supermarkets, eg. Sell By 12/06/07
The food industry calculates these Sell By Dates by using a technique called Challenge Testing. The Meat we purchase in our local supermarkets was once an animal that was slaughtered, processed and packaged before we pick it up off the shelf at ASDA or Tesco. When the meat is packaged it is already contaminated with bacteria. Over time these bacteria feed off the meat ,multiply and grow : we precieve this as discoloration or mould formation on our food. After time the bacteria and grown so much that the food is no longer good to eat, when this happens the food is called spoilt or off.
The time taken for the meat to go off depends upon the environment the meat is placed in, bacteria will grow quicker in higher temperatures for example and so will go off quicker in higher temperatures. The Sell By Date printed on our meat packets is calculated on the assumption that the meat will be exposed to certain conditions, for example that meat will always be refrigerated at 10oC from the time it leaves the processing factory to when we pick it up at the supermarket. This chain of refrigeration is know as the Cold Chain.
The Cold Chain of the Food Industry is highly regulated and developed but what happens after we pick it up from the Supermarket Shelf? The Food industry has addressed this problem using their Challenge Testing technique, which involves conservative estimates of when food will spoil as to avoid people eating off meat. This means that often the printed cell by date insinuates meat is off when in fact it isn't.
This initial phase of cell by date hopes to improve on the printed Sell by Date by using predictive microbiology instead of Challenge testing as a basis. Starting with an intial CFU (representative of initial contamination) & constant temperature we want to look at how long it takes for the OD of the colony, represetnative of the CFU of bacteria in meat, to reach a level equivalent to the point where the meat is considered to be spoilt. Using this level and other data collected through preliminary experimentation we hope to set up a model representative of the transient response of our system which if validated will serve as the basis for the later phases of Cell By Date.
Quantitatively our design parameters are:
- Initial CFU : To be taken from Predictive Microbiology Papers / FSA ??? What is this ???
- Temperatures : Focus on 2 temperatures
- 4oC representing Cold Chain best case scenario (constant refrigeration)
- 40oC representing Worst Case scenario (constant heating)
- Spoilage Level : Due to time constraints we are unable to wait for the CFU of our colony to be equivalent to the level where the meat is actually spoilt as this would take days to achieve. Instead we will define our own spoilage limit, it will be the CFU reached in 24hr under Best Case Scenario conditions ,eg. constant 4oC, starting with initial CFU taken from papers/FSA. This means that we are taking the maximum life of our meat to be 24hrs. This spoilage level will have to be determined by preliminary experimentation.
Phase 2 : Minced Beef Specific Temperature Exposure Device
2A : Gradient
- The higher the exposure the faster the system will move along a graded colour scheme.
More info to be added!
2B : Discrete Colour Change
- Builds on 2A by having a discrete colour change when meat is spoilt.
- Discrete Change occours when meat is exposed to room temperature (25oC) for more than two hours
More info to be added!
Phase 3 : General Meat Heat Exposure Device / Abstraction for re-usability
More info to be added!
Chassis Focus
The Table below outlines which Levels which hope to implement in different levels of Cell By Date in.
| Chassis | Phase 1 | Phase 2 | Phase 3 | |
| E.coli | X | |||
| In-Vitro | X | X | X | |
| In-Veso | X | X | X |
