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Influence of modern technologies of processing, storage and distribution on food propertiesPresented at
Carlo R. Lerici We are emerging from a period of about 25-30 years in which, in order to minimise damage in food, highly selective processes were developed to obtain high quality food products, reducing the undesired side-effects. These results were obtained mainly by:
Now we are entering an era whereby the quality of food must be raised by maintaining or improving not only typical attributes for food, such as microbiological or toxicological safety, nutritional value, sensory properties (such as taste, flavour, texture, appearance and colour), but also its health promoting property (e.g. antioxidant capacity). Without going into detail about quality concept and where, in the food chain, the quality is improved or, on the contrary, compromised, in our view the most important attributes for a food product are (Lerici,, 19971): sensory properties (taste, flavour, texture, appearance, colour); microbiological (absence of pathogens and microbial toxins), and toxicological safety; nutritional value; convenience and shelf life; healthiness, considered as "health promoting capacity". Healthy attributes of foods have been of interest for a long time. The fight against nutritional deficiencies started centuries ago and it is still in progress. In the meantime, unbalanced diets are recognised as being related to chronic diseases. Excess energy, a dietary fat composition with high levels of saturated fat, low dietary fiber intake and low fruit and vegetable consumption, seem to be related to the development of serious human diseases, such as cancer (Langseth L., 19952) . During storage and processing of foods many changes occur in their physical and chemical properties. The effects of processing on nutritive factors such as vitamins and minerals, as well as in sensorial properties, in the last decades have been deeply studied. The consequence has been a pronounced improvement of the overall quality of the processed foods available nowadays in industrialised country. It is, however largely unknown how storage and processing affect non-nutritive components, such as flavonoids, carotenoids, catechins, vitamins, lactic acid bacteria and bioactive peptides, all substances recognised as healthy. Hence, the health promoting capacity of stored and/or processed foods in the diet is still largely unknown (van Boekel and Jongen, 19973). In order to evaluate the healthiness of raw food and to optimise processing conditions, the health promoting capacity and changes in it during storage and/or processing have to be measurable. Examples of measuring systems are lipid oxidation tests for antioxidant overall activity, oxygen consuming capacity, radical scavenging capacity, Ames test for mutagenic and antimutagenic activity, tests for various bio-activities. Main sources of pro-oxidant factors and antioxidant defences are reported in table 1 (Lanseth, 19952). From the technological and nutritional points of view, the presence of natural antioxidants can be considered important both for food preservation and human health (Giese, 19964).
Table 1 Amongst the naturally occurring antioxidants are carotenoids which play a prominent role due to their abundance in fruit and vegetables (table 2). However, over 600 different carotenoid molecules are contained in fruit and vegetables, providing a beneficial effect on their own or through interactions with each other vitamins. For this reason, the detection of carotenoid concentration alone is not a sufficient indicator of the real health protecting potential of food. A more effective tool for evaluating overall antioxidant activity is to measure the radical scavenging and reducing properties of the food. On the contrary, the evaluation of the overall antioxidant properties through the measurement of the radical scavenging and the reducing properties of the product is considered a suitable tool for this purpose (Nicoli et al. , 19975). It is generally recognised, but poorly investigated, that storage as well as processing can negatively affect the original antioxidant properties of raw material. In fact, food processing, especially if heat treatment based, can result in undesired reactions, mostly of a chemical nature. For instance, oxidation can occur as the consequence of antioxidants and vitamins depletion. On the other hand, heating can also induce the formation of compounds with new antioxidant properties, as occurs during the development of the Maillard reaction (M.R.) in which a reducing sugar reacts with amino groups. Properties of Maillard reaction products (MRPs) are very interesting in food processing and preservation, because they positively or negatively affect nutritional and sensorial properties, and shelf life of the products (Lerici and Giavedoni, 19946). In fact, MRPs have an effect on the nutritive value (loss of the essential aminoacid lysine), as well as the development of new compounds which improve flavour and colour in many food products during baking, cooking, roasting or frying. Although they have been extensively studied for, it is not still clear whether the M.R. produce mutagenic or antimutagenic compounds or substances which favour or block microbial growth or enzymatic activity (Lerici and Nicoli, 19967; Stecchini et al., 19918; Nicoli et al., 19919).
Table 2 The antimutagenic activity has been recently attributed to the antioxidant activity (i.e. chain breakers, oxygen scavangers and/or metal chelating agent) observed for some MRPs ( Anese et al., 199411). Over the last few decades, extensive research work has been carried out on the antioxidant properties of MRPs. experiments, mainly carried out on model systems, shoved that MRPs exhibit antioxidant properties in heat treated lipids (Elizalde et al.11, Severini and Lerici et al., 199512). There is little data available on changes in the antioxidant loss due to processing and/or storage nor on the simultaneous formation of MRPs with antioxidant properties following heat treatment. According to Nicoli et al., 19975, although natural antioxidants can be lost during heating, the overall antioxidant properties of food can be maintained or enhanced by the formation of new antioxidants such as the MRPs. Analysis of coffee beverages confirmed that total antioxidant. In tomato juice, the heating caused an increase in its antioxidant potential, even if short heat treatment causes an initial reduction in the original antioxidant property, probably due to formation in the early stages of the Maillard Reaction of intermediate compounds with pro-oxidant activity (Nicoli et al., 19975). Analysis of coffee beverages confirmed that total antioxidant properties were greatly increased with degree of roasting (Nicoli et al., 199713). Nowadays, the directions in healthy food productions are the dietetic foods (slimming, low fat and low sugar content products), meal replacement products and fortified, by vitamins and mineral, foods (Korver, 199714). In our opinion, strong attention should be paid regarding traditional foods and recipes, being the result of a selection of many centuries. A joint research programme between University of Udine and Chinese Academy of Science (Institute of Botany of Beijing, China) on healthy properties of Chinese wild plant, is now beginning. The research, supported by World laboratory Organisation, will consider short-medium period of stay of researchers of Udine University in China and of Chinese researchers in Udine. In conclusion, the "health content" of raw or processed food should be preserved or enhanced by improving all the operations connected with the food chain, i.e. production, storage, processing, packaging, transport, distribution and home handling. In this way, it will be possible to combine healthiness with safety and, in other words, to pursue the real total quality of foods. References
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