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39 Cards in this Set
- Front
- Back
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What's the premise with commercial sterility? |
If there are 10^6 spores in a can, reduction by 12 logarithmatic cycles to 10^-6 represents commercial sterility: 1 in 10^6 cans 12D process
Already beyond the worst case scenario. |
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What is the D-value? |
Decimal reduction time. The time needed to reduce the microbial population by one log unit. |
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How is D-value known? |
It is a character of each organism. Different by individuals. By experiments of standard plate count. |
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What's the relationship between death rate and temperature applied to the microorganism? |
Death rate increases exponentially with increasing temperature. |
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What's the relationship between D-value and Temperature for the same organism? |
Higher temperature, smaller D-value. |
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What's a z-value of the organism? |
thermal resistance. The relationship of D-value and temperature Z=T2-T1/(logD1-logD2) |
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What's the concept of equivalent heating processes? |
Different temperature/time pairing might result in same lethality of microorganisms |
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Which of the two equivalent heating processes is better in preserving food quality? Give an example |
Higher T, shorter t. Milk when higher T shorter t: preserve quality but otherwise, maillard reaction, produce off-flavored brown milk. |
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What are the corresponding psi(pound per square inch) of steam under pressure: 10 psi, 15 psi and 20 psi? |
116C, 121C, 127C. |
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What's the drawback of highT short t processing? |
More precisely controlled, expensive equipment needed |
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What are the two types of thermal processing? Which is better for canning and which for HTST processing? |
Conventional: seal, then process, for traditional canning Aseptic: Process, then seal. better for HTST processing |
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What's the simplest equipment for canning? |
batch retort. Big pressure cooker using pressured steam |
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What's the process of batch retort? |
Cans filled and sealed and loaded batch retort sealed and filled with steam retort held at temperature (hold time) finished, turn off and load cold water unloaded at room temperature |
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What's the function of thermal process calculations? |
To determine the hold time needed, taking into account of the come-up and come-down times, and the z-value aka thermal resistance. |
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What is used to measure the heating up, or heat penetration of the contents? |
Thermocouples are inserted into cans, hooked up to a data logger. |
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Where are the thermocouples placed in the cans? Why? |
At the cold point: the place where that is heated up the last. To ensure everywhere in the food particles is heated to the required temperature. |
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Where is the cold point in the food? |
If solid, in the center, middle If liquid-containing: In the center, 2/3 down due to convection |
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How is the heat transfer rate in the food different with different foods? |
Solid: conduction is slow Liquid: Convection is fast: hotter contents goes up. But more viscous, the slower. |
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Give an example when the heat transfer characteristics change during heat processing. |
Starch, undergoes gelatinization during heat processing, and more viscous, slower transfer |
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When is thermal process investigations and calculations required? |
When package: size, characteristics, or product formulation changed |
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How is the thermal process data in practice? |
Extensive standardized data available. |
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What is the process of aseptic processing? |
Food thermally processed Filled into pre-sterilised can Sealed by pre-sterilized closure In a sterile environment (free of microorganisms) |
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What is the aseptic thermal processing first used at? |
Milk. Pasteurized milk packed into sterile containter. |
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What are the evolutional stages of milk aseptic processing? |
1) Batch processing: 62.5C for 30 min pasteurization, then package 2) 30s: HTST pasteurization: 71C for 15s, cooling to 2C, package 3) 70s: UHT(ultra-high-temperature processing): >100C for 1s, rapid cooling and aseptic packaging. |
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What's the thermal machinery generally used by North American for milk processing? |
Plate heat exchanger |
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What is the benefit of UHT processing? |
Commercially sterile when not opened. No refrigeration required before opening. Eg. small packs of milk or cream on table |
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How is the current evolution of aseptic processing? |
To encompass more viscous and particulate food products. |
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What are the advantages of aseptic processing, compared to conventional? |
Can reach high T and efficient heat transfer mechanisms. Continuous process. Not constrained by the container. |
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What is a tetra brik? |
Folded sterile package make from on site laminate of cardboard, aluminum foil and plastic. |
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What is often the packaging of aseptic processing? |
on-site package forming |
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What is the production line sequence in aseptic processing? |
Sterilize product, on-site formation of packaging, sterilize package, filling aseptically. |
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What is the rate of packaging in aseptic processing production line? |
20,000 per hour. |
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What are the common sterilizers on aseptic processing production line? |
Hydrogen peroxide, UV light. |
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How is Tetra brick better than cans? |
Save cost in storage and transportation. Takes up less room |
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What types of packages can be formed on-site? |
Pouches, plastic bottles, coffee creamers, trays |
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What's the determining factors as to which thermal processing is adopted? |
Economics, and product characteristics: certain complicated aseptic processing only specific to some products/packages |
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What are the alternative non-heat thermal processing? |
Microwave, Ohmic heating using electricity Pulsed electric fields. |
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All thermal processes require________ and ______ to ensure commercial sterility and pasteurization. |
Stringent evaluation and validation |
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There's a substantial level of GOV _____ over thermal processes |
regulatory oversight |
