Food Chain 2004: Summaries of Session 4

Molecular Strategies to Improve and Control Meat Quality

Professor Roberta Davoli, Department for the Protection and Improvement of Agricultural Food Products, University of Bologna, Italy

Most people like their meat and they like it tender, juicy and well flavoured. We all know that this is often not the case and we complain to the butcher. However, the potential to have better meat quality is increasing all the time due to an improved understanding of the genetic basis of meat quality. This is tackling the very soul of the problem according to Professor Roberta Davoli, from the University of Bologna.

To date the most important applications of molecular genetics in meat relate to improved pork meat quality, more tender beef, and in the traceability of meat origin which has major consumer confidence and food safety implications. The advent of molecular genetics is a major advance over the use of classical genetics in an animal breeding sense as it complements the latter, and supplies tools to work at DNA level with the possibility to detect the individual genes influencing the quality characteristics of meat.

A better knowledge of the genetic make-up of the animal and establishing maps of the genes are essential prerequisites in order to isolate and characterise genes of interest. This, in turn will allow the selection of animals with the required meat quality traits.

Pale, soft and exudative (PSE) muscle is a major quality defect in pork meat that results in an unacceptable appearance for the consumer and a lower yield in cooked ham production i.e. it has major economic implications. Occurrence of PSE can be up to 90% - 95% in stress-susceptible pigs but such pigs are 3% - 4% leaner with less back fat and larger loin eyes and hams.

Stress susceptibility is controlled by the so-called halothane gene which has positive and negative effects as shown above. The mechanism involved in the effect of the halothane gene on pork carcass leanness and meat appearance remains to be elucidated but is the subject of extensive research in a number of countries including Ireland. Positive outcomes from this research should virtually eliminate the PSE problem.

In beef animals, muscle fibre characteristics are involved in meat tenderness and flavour but currently the impact of muscle type on lean meat quality is not well understood. However, with the use of DNA and related techniques a new insight into muscle physiology is being obtained which will have major follow-on economic benefits in terms of producing leaner beef cattle that give tender meat, i.e. the tough steak may be a thing of the past.

A third major application of DNA technology is in meat traceability. Consumers increasingly want to know the origin of the meat they purchase spurred on by fears engendered by the BSE and foot and mouth scares. Genetic identity cards are being produced for each animal which enable it to be traced through the production and processing chains, and on to the thin beef slice purchased by the consumer. Versions of this technology are currently available but new and better systems are evolving. This will ensure consumer confidence in the product they buy and will foster producer-retailer-consumer continuity, i.e. repeat purchases.

New Evidence on Delivery Systems for Probiotics

Dr Paul Ross, Joint Research at the Teagasc Biotechnology Centre, Fermoy and the Alimentary Pharmabiotic Centre, UCC.

According to Dr Paul Ross, probiotics are live ‘friendly’ bacteria which when consumed in adequate numbers confer a health benefit in man. Probiotic bacteria have a number of shared characteristics including their ‘generally recognised as safe (GRAS)’ status, their human origin and their acid and bile tolerance. Following ingestion, the probiotic bacteria must reach the human gut alive which is easier said than done.

Many consumers are aware of the increasing evidence for the beneficial effects of probiotics and most are sold as dried products or in fermented dairy products such as yoghurt. Typical probiotic bacteria are the so-called lactobacilli and bifidobacteria species, and probiotic-containing foods form a major segment of the functional foods market.

Dr Ross pointed out that the natural location of probiotic bacteria is in the human gut and so it is not surprising that they perform poorly when grown in the laboratory or the factory. Consequently commercial strains must be selected on the basis of their technological stability (i.e. during food processing) in addition to their health promoting effects. The inability to deliver the required amounts (up to 10 million bacterial cells per gram of food) of certain strains has resulted in them being overlooked for probiotic applications.

However, this is now changing as a result of successful research outcomes. For example, some of these strains respond positively to outside stresses such as sub-lethal heat or salt treatments, i.e. their viability is increased. Another involves encapsulating or cocooning the bacteria with a coating that protects during processing and gastric transit, and remains intact until the probiotic reaches the human gut.

A greater understanding of the genetic make-up of the probiotic bacteria means that many are now amenable to genetic manipulation, thus opening up new possibilities for improving their functional properties and survival during processing and in the human digestive system.

Finally, Dr Ross stressed that these approaches will improve the efficacy of existing probiotic bacterial strains, and will also facilitate the exploitation of hitherto uneconomic sensitive strains leading to a new generation of probiotic food products and improvements in human health.

Engineering Solutions for the Food Factory of the Future

Professor Dietrich Knorr, Department of Food Biotechnology and Food Process Engineering, Berlin University of Technology, Germany

High intensity electric field pulses, high pressure, and ultrasound are three technologies that are finding increased application in food processing and transformation reported Professor Dietrich Knorr from Berlin Technical University. Until recently these technologies were used to replace conventional processes such as canning in order to reduce process intensity, save energy, reduce waste and to provide products with better nutrient and quality retention for the consumer. However, new uses are now being targeted.

For example, treatment with pulsed electric fields can increase oil yields from oil seeds and also higher yields of oil constituents such as phytosterols. High pressure treatment has been used to increase metabolite (e.g. human health promoting substances) production in plant cell cultures and to increase temperature resistance of probiotic bacteria thereby enabling them withstand heat treatment of the dairy product that carries them.

The new techniques have particular application in the low energy processing of food. Sugar beet is conventionally pretreated at 80°C for 10 min to break down the cells and facilitate sugar extraction. Pulsed electric field treatment has the same effect but reduces the energy requirements by 40%. A similar amount of energy is saved in the dehydration of vegetables that have received the pulse treatment while pasteurisation of foods can be conducted with an energy saving approaching 60%.

High pressure treatment, as the name suggests means subjecting foods to pressures of up to 10 tonnes per square centimetre in special equipment. This inactivates bacteria but results in good retention of nutrients and flavours. Processing times are quite short. Applications currently on the market include orange juice and high quality preserves. High pressure is also used in food freezing and when the pressure is released the food freezes instantly with very small ice crystals which cause minimal structural damage (for example to texture) compared with conventional freezing where ice crystal formation is slower and the crystals are larger and more damaging.

High pressure is very useful for the selective inactivation of bacteria. For example, in a probiotic food the requirement during processing is to kill the bad bacteria while retaining the ‘friendly’ ones. High pressure can also act synergistically with pulsed electric field treatment to achieve an even greater selectivity. The gelatinisation of food starches is important for the generation of texture in many food products. Achieving gelatinisation using high pressure rather than heat results in different properties in the starches, which means new applications and new textures, so lots of exciting developments from the use of ‘pulses and pressures’!!

Main Issues and Opportunities in Embracing Innovative Technology along the Food Chain: A New Member State’s Perspective

Dr Peter Biacs, Ministry of Agriculture and Regional Development, Hungary

Hungarian consumer demands are motivating research and development efforts to establish new methods and the use of novel technologies for supplying fresh and fresh-type foods to the market place. Requirements for market success may vary between the new Member States, however, the general approach is to accept the need to have an innovative food industry with food safety as a top priority, reported Dr Peter Biacs from the Hungarian Office for Food Safety. Within the Central and Eastern European countries the Hungarian agri-food sector has a 71% share of total employment resulting in 5.5% of the GDP.

Corresponding figures for Poland are 18.1 and 3.8%, for the Czech Republic 5.2 and 3.7%, and for the EU as a whole 5% and 1.6% respectively; these reflect major differences between countries and regions.

Hungary has favourable conditions to increase food production and to export to the old and new EU states and to countries outside the EU, but the major challenge is to stabilise product quality and safety. Similarly in Poland, but the Czech Republic, Slovenia and Slovakia have less resources (i.e. less arable land and a poorer growing climate) to develop their agri-food industry. Baltic countries are developing their meat and dairy industries but are less productive in fruit and vegetable growing.

Other countries in Eastern Europe are still facing food security problems and so focus on cereal production and processing. Possible future visions for the food industry in the new Member States embrace integration, activation and knowledge intensity. Integration can be led by the food industry or by producer co-operatives while activation involves the formulation of collective strategies. This will determine whether the community of food producers remains split or whether the ones left behind will have to rely on catch-up technology and product development.

A high level of knowledge intensity is imperative for the development of a marketable and competitive agriculture and food industry in Hungary and in the other new Member States. This applies especially to the introduction of new food processing technologies and formulation procedures that will generate an extensive range of added value prepared consumer products.

Dr Biacs stressed the importance of novel minimal food processing techniques in the development of an innovative added value food industry in the new Member States. This includes minimal processes, high-pressure processing, the use of high-electric field pulses, irradiation and novel packaging systems but added that these will be difficult to introduce bearing in mind the structures prevailing currently in the agri-food sector. Potential products include fruit juices/purees, fermented dairy products, products based on liquid egg, irradiated black and red pepper, and in the longer term ready-meals and other convenience foods.