Gas permeable packaging
Aerobic bacteria can grow. Fresh meat packed in cellulose film so as used in tray packaging is threatened by Pseudomonads like Pseudomonas fluorescens and Pseudomonas fragi as dominant bacteria producing smell and slime.
Gas barrier, closed packaging
The atmosphere in the packaging can be modified according to the food which is being packed.
Enzymes, temperature and competitive growth can produce gas like CO2.
For some food gas packaging with modified atmosphere are used.
Vacuum packaging
Vacuum inhibits the growth of aerobic microbes such as Pseudomonas,Bacillus, moulds. In these packagings the growth of lactobacillus is dominant. Enterobacteriaceae can grow under anaerobic conditions.
Modified Atmosphere Packaging MAP
Nitrogen, CO2 and in some cases O2 are used.
Nitrogen has no activity against bacteria. It increases shelf life substuting oxygen.
CO2 acts bacteriostatic on gram negative aerobic bacteria and bactericide because of its undissociated part of H2CO3 which enables CO2 to trespass the cell membrane and act bactericide on the cells of the bacteria.
Lactobacillus is not affected by CO2.
CO2 can reduce growth of Listeria on meat.
| Polymer | used as | Filling product |
|---|---|---|
| PVdC,EVOH,Acrylnitril | Oxygen barrier | |
| PET/PVdc-PVC/PE | multilayer foil | red meat |
| HDPE, PVdC,PP | water vapor barrier | |
| PA/PE-PVC/PE | multilayer foil | treated meat |
| HDPE,PP | stability,suitable | |
| for microwave oven | ||
| PET/PVdC/PE | multilayer foil | poultry |
| Nylon | high temperatures | |
| resistant | ||
| PET/PE/PVdC-PVC/PE | multilayer foil | fresh fish |
| CPET | mechanical resistance, | |
| high temperatures | ||
| resistant, oxygen barrier | ||
| PET/PVdC/PE | multilayer foil | Pizza |
| APET | mechanical resistance, | |
| oxygen barrier | ||
| PET/PE/PCdC | multilayer foil | Cheese |
| Polyester | high temperatures | |
| resistant, flexibility | ||
| and resistant to perforation | ||
| Metallized PET/PE-metallized PA/PE | multilayer foil | dried products,coffee |
| PVC/PET | mechanical stability, | |
| some types | ||
| Micropore foil-LDPE/OPP/PVCPA/PE | multilayer foil | fresh vegetables |
| LDPE, HDPE, EVA | sealing layer | |
| EVA | highly permeable to | |
| oxygen and CO2 |
Multilayer foils may have PE, PVdC and PET as typical components.
Packaging as short news:
- Plastic bags are bad because they may contain PVC which develops toxic gases as it is burned. Use paper bags.
- Aluminum cans are hostile to environment because they can hardly be recycled.
- Greaseproof paper is better as plastic foodwrap because the later may contain harmful softener
Nonylphenol in food
Nonylphenol is an industrial chemical which interacts with human hormones and produces cancer. Its synonyms are p-nonylphenol,4-nonylphenol, C15H24O. Nonyphenoles were found in mineral waters due to migration from the plastic seal of the caps of bottles.
Another source of nonylphenol in food are the nonylphenolethoxylate which are used in the production of plastics for wrappings and packagings of food. Nonylphenolethoxylate act as emulsifier and stabilizer in plasticizers for Packagings. Nonyphenoles are breakdown products of norylphenolethoxylate detergents used in household and industrial cleaning products.which contaminate food. Their contact with foods leads to the contamination with nonyphenoles.
Very high amount of nonylphenoles were found in apples and in tomatoes by the Research Center in Julich.
The estimated human intake of nonylphenoles is 7.5 microgram a day. The content of nonylphenole in pesticides are now being analyzed.
| Product | Modified atmosphere | Remarks |
|---|---|---|
| Red meat | 80% O2 + 20% CO2 | CO2 reduces growth of Pseudomonas |
| aerobic bacteria which often | ||
| spoils red meat.High concentration | ||
| of oxygen is needed to keep red colour. | ||
| Porc | 60% O2 + 40% CO2 | CO2 reduces growth of aerobic bacteria |
| less O2 is needed because of reduced red | ||
| colour of porc compared with beef | ||
| Poultry | 50 – 80%CO2 + 20 – 50% N2 | A high headspace with gas is important |
| Sausages | 20% CO2 + 80% N2 | |
| Sliced heated meat | 20% CO2 + 80% N2 | |
| Fish, high-fat | 60 – 70% CO2 + 30 – 40% N2 | No oxygen should be used |
| to reduce rancidity | ||
| Fish, low-fat | 30 – 40% O2 + 30 – 70% CO2 | Oxygen is used to keep red |
| + 0 – 40% N2 | colour of low-fat fish and seafood | |
| It also reduces growth of anaerobic | ||
| bacteria such as Clostridium | ||
| and its toxins | ||
| in case of long shelf life | ||
| Sliced fish,cooked | 20% CO2 + 80% N2 | |
| Hard Cheese | 80 – 100% CO2 + 0 – 20% N2 | |
| Sliced hard cheese | 80 – 90% CO2 + 10 – 20% N2 | |
| Soft cheese | 20 – 40% CO2 + 60 – 80% N2 | |
| Gateau | 50 – 70% CO2 + 30 – 50% N2 | Storage at +4 – +7 C |
| Cake and bread | 20 – 40% CO2 + 60 – 80% N2 | |
| Pizza | 30 – 60% CO2 + 40 – 70% N2 | |
| Pommes frites | 70 – 80% CO2 + 20 – 30% N2 | |
| Salads with dressings | 100% N2 |
Some special remarks concerning CA packaging (Controlled Atmosphere packaging
Spoilage of food can be caused by:
- The nature of bacteria and their amount.
Bacteria can be aerobic, growing in presence of oxygen such as Pseudomonas, Acinetobacter and moraxella.Or they are anaerobic, growing in absence of oxygen such as Clostridium producing toxins and Lactobacillus producing lactic acid. - Water activity aw
- pH
- Cell breathing
- Composition of the food
- Storage temperature.
Low temperatures reduces bacteria growth.
Some bacteria grow even under low temperatures, the psycrophilic like Pseudomonas - Hygiene during production
Bacteria can be present in the raw material,additives and environment, such as our skin,used utensils and air. - Gasatmosphere
oxygen can cause rancidity, oxidizes vitamins, Nitrogen can replace oxygen.
Oxygen is sometimes necessary to keep the red colour of fresh meat.
The choice of the gas to be used during filling is therefore very important and varies from one food to another. - Good Manufacturing Practice
CO2 reacts with water forming carbonic acid which increases acidity of the product reducing bacteria growth.Nitrogen can replace CO2 In Products such as cottage cheeseand dairy cream CA packaging with nitrogen instead of oxygen is being used. Hard cheese is packed under up to 100% CO2 to reduce bacterial activity and stabilizes consistency of the product. Soft cheese is packed under 20 – 40% CO2 because otherwise the packaging would shrink because the gas gets in solution with the product.In this case 30% of of CO2 should not be exceeded.