The more common industrial gases typically employed in the production of safe food include nitrogen, CO2, oxygen, SO2, ozone and hydrogen.
These gases are used to provide improved functionality of food ingredients like cryogenically crystallized fats which can increase the shortening power by 30% due to it’s unique crystal morphology.
Rapid freezing and chilling can also improve the product quality by reducing dehydration losses and reducing the risk of ‘freezer burn’.
By reducing temperatures of fresh products like poultry from 10°C to -1°C deep chilling can be achieved in less than 2 hours hence substantially reducing the risk of microbiological spoilage and increase the shelf life.
Yield improvements of up to 4% can also be realized by for instance crust freezing small goods prior to slicing in high-speed slicers.
During mixing and grinding a significant amount of heat is generated, and CO2 chilling processes can offset this added heat load and also further reduce temperatures for optimum forming or further processing.
Equipment has been developed to meet all the processing and quality requirements, whether batch or continuous processes.
These include batch freezers and continuous belt freezers like tunnel, spiral and fluid bed freezers to deliver individually quick frozen value added products.
Automated CO2 based chilling equipment has been specially adapted to suit in-process requirements and conditions. CO2 chilling systems fitted to blenders have the capability to control the temperature to 0.1°C.
All this equipment has been designed to allow for easy internal access for the purpose of sanitation.
Gas mixing systems have been specially designed to consistently supply the required gas mixes and flow rate required for modified atmosphere packaging.
In the wine industry, the control of wild yeast can be maintained by an accurate S02 dosing system, critical where tight limitations exist for the presence of residual SO2 in food stuff.
BOC also offers a comprehensive range of on-site technical support and services including safety training, safety audits as well as advice on HACCP conformance and instituting critical control points.
Process audits assess the efficiency of gas related applications and provide recommendations of how to improve yields, reduce costs and improve food safety.
In the first stage, or in the case of minimally processed food, the predominant needs are to rapidly reduce temperatures and/or control the atmosphere to prevent microbial spoilage or senescence.
Products like oil are prone to oxidation of the fatty acids, and hence need to be blanketed in a nitrogen atmosphere.
The presence of oxygen in MAP gases can reduce the risk of botulism in seafood and hence severe food poisoning.
CO2 when dissolved in aqueous solutions forms a weak acid inhibiting microbial spoilage and also anaerobic conditions which in turn inhibit aerobic microorganisms.
During sparging applications nitrogen is used to sparge liquids like wine and oils to remove dissolved oxygen which can potentially degrade product.
In modified atmosphere packaging, gas mixtures are specifically tailor made to target the predominant spoilage mechanisms and hence enhance shelf life and provide another hurdle for reducing microbial spoilage.
Temperature control is as critical to extend shelf life and inhibit spoilage mechanisms in the case of produce as well as primary meat production facilities.
Dry ice or CO2 snow may be applied to grapes during harvesting for rapid chilling or applied into combo bins or trays to chill poultry prior to distribution to secondary processing facilities. Particularly poultry is prone to microbial spoilage if insufficient heat is removed from the carcass by the spin chillers, and hence dry ice or CO2 snow can rapidly reduce the temperature below 4°C, to inhibit the onset of spoilage and enhance shelf life.
A very diverse range of innovative solutions has evolved over recent years covering atmosphere, microbe and temperature control. In conjunction with local and overseas research organisations new technologies continue to emerge.
In wine processing, levels of dissolved oxygen are continually monitored and both gases CO2 and N2 are used in varying ratios to control dissolved levels of CO2 and oxygen, depending on the type of wine that is being produced. This results in a wine with an extended shelf life and the desired flavour profile and functionality.
Hydrogen is used in the hydrogenation process to change liquid into hard fats by changing the molecular structure whilst the high solubility of C02 in aqueous solutions (1 volume to 1 volume at 1 atm) provides soft drinks with the effervescence and slightly acidic taste.
Sulphur Dioxide and Ozone, a strong oxidising agent, have strong anti-microbial properties and are used in food preservation, preventing cross contamination and sanitising processing equipment.
Temperature control during processing is also very important and can impact on quality, yield and food safety.
Temperatures in blenders for beef patties manufacturing have to be controlled within 0.1°C, at a maximum temperature of -1.2°C in order to achieve a coined edge Pattie during the forming process.
Bottom injection of liquid CO2 via injection nozzles at the bottom of the blender delivers CO2 snow at a very high rate achieving rapid and uniform temperature throughout the mix.
Viscosity control allows for the control of the CO2 to be injected at the exact amount to achieve the target temperature.
The temperature of some dough like cookie dough is critical, and fluctuations especially due to ambient conditions can result in increased rejects, production losses and quality issues.
By reducing the temperature of the flour, the main ingredient in pneumatic conveying systems, the dough temperature can be maintained at the target temperature irrespective of seasonal fluctuations in temperatures.
Optimizing the temperatures so that the product or product surface is more rigid for a cleaner cut can attain improved slicing and dicing yields.
A cryogenic spiral freezer can ensure that the product temperature is brought down to near 0°C to ensure a clean cut and reduce yield losses by as much as 4%.
The final product is packaged and sold as either a ‘fresh’ or frozen commodity.
Fresh products stored at either refrigerated or ambient temperatures, can benefit from modified atmospheres, and hence extending shelf life.
The drivers for increasing shelf life may be financially driven, or improved market penetration, or simply another hurdle to improved food safety.
For example, red meat for retail display is commonly being packaged centrally rather than in retail stores.
Centralised packaging is growing in popularity, as it requires less labour, equipment and also a reduced risk of microbial contamination.
Consumers associate the bright red colour in red meat with freshness and this can be attained with high oxygen MAP gas mix, containing also CO2.
The Carbon Dioxide inhibits bacterial spoilage whilst the oxygen is needed to give the bloom that appeals to customers.
A wide range of equipment exists for temperature control covering both chilling and freezing. Cryogenic freezing involves a rapid temperature reduction using specialised equipment to a final temperature of -18°C or colder, and in the case of chilling to below 4°C.
Due to the cold operating temperatures within the freezers, dehydration is substantially less than in conventional freezing equipment, and there is a reduced risk of spoilage of food due to the rapid temperature reduction.
For individually quick frozen products like pizza topping or diced cooked poultry, fluid bed freezers have been developed which have superior performance over other equipment.
The product is initially immersed in liquid nitrogen, to be crust frozen, to prevent product from clumping followed by further heat removal in a fluidised bed.
Cryogenic freezers are typically a quarter of the capital cost, and with a much smaller foot print than conventional system, the added flexibility allows customers to trial new products, and adapt to changing market conditions.
The final product may be transferred into tankers or into storage silos or tanks.
Wine or fruit juice transported in bulk must be protected from oxidation and is blanketed in a nitrogen or CO2-atmosphere.
Atmosphere control in cool rooms is commonly employed to extend the shelf life of apples and other fruit, and hence extend the availability of these perishable products.
Oxygen is used in the aquaculture industry to transport live fish.
In transit refrigeration in trucks using CO2 or N2 provides increased flexibility and more rapid temperature pull-down, and can provide back up if the mechanical refrigeration system fails.
In transit refrigeration with CO2 snow is commonly utilised where products require chilling from loading through to delivery to the customer.
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