Continuous-flow heat processing 471 stable but the oxidised form is much more heat labile. losses of vitamin c are therefore related to the degree of oxidation of the vitamin rather than to the sever ity of the heat process(Burton, 1988). This is known to apply to other products especially fruit juices(Ryley and Kadja, 1994)and vegetables 6. There are some vitamin interactions which occur In milk, vitamin BI and ic acid interact with vitamin c during heat treatment so that losses of these vitamins again are not a simple function of the degree of heat treatment. Folic acid is protected by ascorbic acid, the reduced form of vitamin C, which, if oxidised, will lead to higher losses of folate. Vitamin B12 losses depend on the oxidative degradation of ascorbic acid, so these losses depend on the availability of oxygen and ascorbic acid, as well as on the thermal process Although these changes are dependent on the degree of thermal process applied to the foodstuff, the remainder of the process must also be considered when evaluating the nutritional quality of the product. Changes during storage of the product over the usual three to six month shelf-life at ambient temperatures can be considerable, even though the container is designed to exclude light and oxygen. In addition, there is usually some pre-processing during manufacture of products; for instance, soups, stews and cook-in sauces are usually cooked or fried before sterilisation. Finally, handling of the product in the home is usually out of the manufacturer's control and overheating or long standing time at warm temperatures can easily have a more severe effect on nutritional quality than any of the procedures described above 22.7 Future trends A relatively new technology will only succeed commercially if it offers benefits to the processor, in terms of operating costs or other means of operation efficiency, or if it offers benefits to the consumer in terms of attributes that they are prepared to pay for. In-container processing using a metal can has a poor image and appears 'old technology, although some development with plastic trays, pouches or bottles is in evidence. Continuous flow heat processing has the advan- age over in-container processing of a fresher image, because the packaging is similar to that used for fresh chilled products. The food then has an improved organoleptic quality if processed correctly but is still ambient shelf stable. The question is whether these advantages will outweigh the disadvantages of increased technical difficulty and increased unit cost, mainly due to the high cost and low filling rates of the aseptic filler. The indications are that the technology will grad- ually displace the in-container process to a degree; the continuous flow thermal processing of low-viscosity liquid foods such as milk, fruit juices, teas and tomato products is already well established and more, generally innovative, food prod ucts are being introduced, albeit at a fairly slow rate. This slow introduction is very useful and may even be deliberate; because the process has a high complex ity a large body of processing experience needs to be built up and consumers are more likely to become accustomed to this type of product.Continuous-flow heat processing 471 stable but the oxidised form is much more heat labile; losses of vitamin C are therefore related to the degree of oxidation of the vitamin rather than to the sever￾ity of the heat process (Burton, 1988). This is known to apply to other products, especially fruit juices (Ryley and Kadja, 1994) and vegetables. There are some vitamin interactions which occur. In milk, vitamin B12 and folic acid interact with vitamin C during heat treatment so that losses of these vitamins again are not a simple function of the degree of heat treatment. Folic acid is protected by ascorbic acid, the reduced form of vitamin C, which, if oxidised, will lead to higher losses of folate. Vitamin B12 losses depend on the oxidative degradation of ascorbic acid, so these losses depend on the availability of oxygen and ascorbic acid, as well as on the thermal process. Although these changes are dependent on the degree of thermal process applied to the foodstuff, the remainder of the process must also be considered when evaluating the nutritional quality of the product. Changes during storage of the product over the usual three to six month shelf-life at ambient temperatures can be considerable, even though the container is designed to exclude light and oxygen. In addition, there is usually some pre-processing during manufacture of products; for instance, soups, stews and cook-in sauces are usually cooked or fried before sterilisation. Finally, handling of the product in the home is usually out of the manufacturer’s control and overheating or long standing time at warm temperatures can easily have a more severe effect on nutritional quality than any of the procedures described above. 22.7 Future trends A relatively new technology will only succeed commercially if it offers benefits to the processor, in terms of operating costs or other means of operational efficiency, or if it offers benefits to the consumer in terms of attributes that they are prepared to pay for. In-container processing using a metal can has a poor image and appears ‘old’ technology, although some development with plastic trays, pouches or bottles is in evidence. Continuous flow heat processing has the advan￾tage over in-container processing of a fresher image, because the packaging is similar to that used for fresh chilled products. The food then has an improved organoleptic quality if processed correctly but is still ambient shelf stable. The question is whether these advantages will outweigh the disadvantages of increased technical difficulty and increased unit cost, mainly due to the high cost and low filling rates of the aseptic filler. The indications are that the technology will grad￾ually displace the in-container process to a degree; the continuous flow thermal processing of low-viscosity liquid foods such as milk, fruit juices, teas and tomato products is already well established and more, generally innovative, food prod￾ucts are being introduced, albeit at a fairly slow rate. This slow introduction is very useful and may even be deliberate; because the process has a high complex￾ity a large body of processing experience needs to be built up and consumers are more likely to become accustomed to this type of product