Specific modifications of cell wall hydrocolloids in a new technique for processing high quality canned vegetables

Because of the results of many years of extensive research work on pectin and pectin enzymes in Hohenheim, the idea that pectin plays a very decisive role in any form of processing of raw plant products due to its function in the unity of the plant tissue gained ground. On the basis of this knowledge a solution for the prevention of the enormous disadvantages of Appert's conventional canning method (namely the excessive softening of the vegetable tissue and the leaching of nutrients) was searched for and found, which took into consideration the characteristic features of the indigenous pectic enzymes and pectic substances in the vegetable tissue. It was realized therefore that one should not - as in the conventional method - indiscriminately inactivate all enzymes during the pretreatment step. On the contrary, through a specific time/temperature-controlled pretreatment one must utilize those indigenous enzymes which initiate specific changes or alterations in the pectic substances which bear relevance to texture. The so altered pectic substances should (in combination with already available or added calcium salts) be prevented from excessive degradation during sterilization - contrary to the conventional method - so that a firming of the vegetable tissue rather results. The product - although well-done - will be crispy in texture. The amount of brine usually used in the conventional method is decreased drastically. And because the cans are vacuum-sealed, the brine which conventionally serves as heating medium is replaced by steam during the preheating and sterilization steps. Both thermal processes take place in the same container. Because of the small amount of fluid there are practically no leaching losses, particularly since this fluid which practically'adheres to the vegetable and renders it juicy is eaten together with the vegetable. Through the absence of leaching losses (and perhaps because of the lack of reaction medium) the aroma, taste and colour were well maintained. The result was a product with excellent sensory quality