Adding value to pork for producers and consumers: enhancing omega-3 DHA and selenium content of meat

Pork is possibly the most versatile raw meat product compared to chicken, beef, turkey and lamb. By utilising sophisticated processing techniques it can be easily transformed and presented across a highly varied range of quality products such as fresh pork, spare ribs, specialist hams, bacon, sausages and salamis. Developing and marketing new pork products is becoming an increasingly competitive activity due to the globalisation of the pig industry and the homogenisation of the markets. Consumers are becoming more particular regarding what they buy; they are not only concerned with the welfare of the animal but the health of their own diets and what nutrients the presented product can offer over and above alternative protein sources.

Meat consumption in the EU and USA (per capita consumption) is 44 kg and 30 kg, respectively, with pig meat consumption being higher than all the other meats. The present and future forecast projection for the EU is 45 kg/hd (Table 1), although this is extremely static when viewed over a 10-year period (Pig Progress, 2001).

For pork to continue to compete successfully in the international and national meat protein market, it must demonstrate an unquestionable stance on safety, quality, convenience, healthiness and price. Recent data compiled by a leading retailer in the UK (Figure 1) clearly showed that pork was seriously failing to attract the contemporary consumer (Smith, 2003). Although this may be specific to the UK market, it should be seen as a warning and acted upon accordingly. To continually improve the image of pig meat and hence consumption it is necessary not only for the retailers but the producers and processors to portray the correct image to the consumer. There is an ever-increasing demand by the public for varied diets containing even safer and healthier foods. Providing the consumer with new and exciting products that can deliver consistent quality and complement an ever-growing need for a healthy diet and lifestyle should be fully embraced. The successful company of the future must create wealth within a very challenging environment, requiring the ability to deal with confusion, unanticipated market movements and rapid change. It is therefore extremely important to develop an entire pork chain that is knowledge-based. Networking is required to provide synergistic benefits through exchange, association and mutuality enabling greater achievements than the individual working alone.

The need for identifying a positive way to promote and re-position pork as a healthy, tasty and nutritious product is of paramount importance and was the key driving force behind the development of Vitapork™. This new product delivers substantial amounts of essential omega-3 DHA polyunsaturated fatty acids together with major antioxidants (selenium and vitamin E). It is believed that Vitapork™ has all the necessary characteristics and final product benefits to fully complement the consumer’s growing appetite for healthy nutritious food.


Table 1. Per capita pig meat consumption projections in the EU, 1999-2008.




Figure 1. Pork customer profile (Smith, 2003).



Consumer behaviour

Meat and meat products are important components in the diets of developed countries and their consumption is affected by various factors such as preparation time, cooking convenience and overall enjoyment. There is also a shift in the type of meat product consumed from fresh to processed products. Consumer needs are constantly changing; and this will be enhanced in the future through increasing disposable income. The consumer has a vast choice of products and must balance lifestyle activities against the need to consume food. An understanding will be required of how product presentation must respond to these trends. In the next 10-20 years a higher proportion of the population will be over 45 years of age, which means that this group of consumers will have a larger influence on pork consumption than the younger generation. The traditions and habits of the consumer will gradually change largely due to the consumers’ lifestyles. Sitting around a table as a family will occur less frequently and therefore eating out, which involves quick, onthe-go consumption of convenience products will become a prominent feature of food consumption.

Over the last 50 years there has been a significant decline in the consumption of omega-3 (n-3) polyunsaturated fats. The main reason for this reduction of omega-3 DHA consumption is the dramatic change in eating habits and more particularly a change in the type of foods consumed. Those food products containing high levels of omega-3 DHA fats such as eggs, offal and oily fish have lost their place in the modern diet. Leading nutritional experts and organisations like the Foods Standards Agency within the UK are now actively promoting the fact that consumers should make every effort to increase their daily intake of omega-3 polyunsaturates.


Omega-3 fatty acids

Fatty acids are the major building blocks of all lipids. Their division into two groups, non-essential, i.e. need not be supplied in the diet, and essential, i.e. must be supplied in the diet, has been known since the early 1930s. Fatty acids not only serve as structural components of all cells but also take part in and are of paramount importance to cellular metabolism. This is particularly so for the essential fatty acids; and ever since their discovery an ever increasing number of roles for them have been found ranging from basal metabolism to the maintenance of health and well-being (BNF, 1992) (Table 2).

The essential fatty acids can be divided into the n-6 group based on linoleic acid (LA) and its longer chain, more unsaturated derivatives, and the n-3 group, which is based on α-linolenic acid (LNA) and its derivatives. Until relatively recently, the balance of nutritional interest was heavily weighted in favour of the n-6 polyunsaturates and their role in health promotion; the imbalance with the n-3 group being of an order of magnitude and primarily due to the consumption of cooking oils and margarines. The extent of n-6 polyunsaturate consumption was such that adverse effects on health were a distinct possibility. Furthermore a comprehensive involvement for the n-3 polyunsaturates in a wide range of health issues and disease prevention was becoming increasingly clear (BNF, 1992). As a result, a far more balanced nutritional strategy in the provision of the two groups of polyunsaturates is now recognised as essential. With the recognition that the groups of polyunsaturates each have their own distinctive metabolic roles and involvements in health promotion, it is also recommended that emphasis on the polyunsaturated:saturated fatty acid (P:S) ratio as a measure of dietary acceptability be reduced and that the importance of the separate n-6 and n-3 fatty acids be recognised through an appropriate total n-6:total n-3 ratio or even an LA:LNA ratio (BNF, 1992; Bruckner, 1992). Furthermore, consumption of n-3 acids should be increased with an aim to achieving an n-6:n-3 ratio of 6:1. The major fatty acid of the omega-3 series, which is seen as being the most important for the body, is docosahexaenoic acid (DHA).


Table 2. Summary of descriptions and roles of omega-3 polyunsaturated fatty acids.

• The omega-3 and omega-6 group of fatty acids are essential nutrients.

• α-linolenic acid is the first fatty acid in the omega-3 group and is the precursor to synthesise DHA, however efficiency of DHA formation is only 5%.

• DHA is a long-chained PUFA and is the most important omega-3 fatty acid.

• DHA is a major constituent of the brain and retina; and is needed for development and maintenance of brain structure and function.

• DHA is an important component of the retina, particularly for infants and the elderly, but also throughout life to help preserve vision.

• Pregnant women, newborn infants, children up to 18 years old and the elderly are key beneficiaries of added dietary DHA.

• Due to a significant change in eating habits, the average intake of DHA in the EU does not exceed 75 mg per day.

• The recommendation is to consume 200-400 mg DHA daily.

Many investigations have looked at the effect of increasing the levels of polyunsaturated fatty acids in pig feed, which has been noted to increase carcass fat content. Feeding linseed oil has been the primary route taken to achieve this natural modification of the fat and muscle tissue. Addition of linseed oil can successfully increase carcass level of LNA (C18:3), the first fatty acid in the omega–3 family. However, this method of dietary modification has minimal effect on the most important and highly beneficial omega-3 long chain polyunsaturated fatty acids (LCPUFA), eicosapentaenoic (EPA, C22:5) and docosahexaenoic acid (DHA, C22:6), in terms of human health and well-being. The reason for this lack of improvement relates to the complicated biochemical process of desaturation and chain elongation, which is required to convert LNA into EPA and DHA. Efficiency of conversion from LNA to EPA and DHA within the pig is no more than 5%, about the same as in the human (Emken et al., 1994). Therefore, the only way of significantly increasing the key LCPUFA, EPA and DHA, in the carcass is by incorporating them directly into the diet.


Antioxidant requirements: selenium and vitamin E

Unsaturated fatty acids are particularly susceptible to oxidation; which is substantially increased in highly unsaturated molecules such as DHA through a cascade of oxidative events. Oxidation is brought about by the action of oxygen free radicals, which naturally occur and potentially accumulate in living and postmortem cells, on the highly unsaturated lipids in the cell membrane and contents (Burton, 1994). The breakdown can be further enhanced by post-mortem handling that facilitates interaction between prooxidant factors and the unsaturated lipids. The accumulated presence of the oxidised lipid metabolites not only poses a potential cytotoxic threat but also reduces product acceptability due to offflavours, rancidity and malodorous compounds.

However, cells have an array of natural defense mechanisms against free radical formation and lipid oxidative damage (Frust, 1996). These consist of concerted enzyme systems that eliminate free radicals and a selection of naturally occurring vitamins and synthesized products, both fat and water soluble, to deter the cascade of events that leads to radical accumulation. Important amongst the former are the enzymes superoxide dismutase, catalase and glutathione peroxidase; and amongst the latter vitamins A, C and E, ubiquinones and a range of natural plant metabolites. The whole sequence of events is further affected by a selection of pro-and antioxidant multivalent metal ions e.g. iron, copper, selenium, zinc. With an increasing interest in the promotion of polyunsaturated components in animal products for human consumption, the lipid antioxidant nutrients, in particular selenium and α-tocopherol (vitamin E), are of major interest for protection against tissue oxidative degradation (MacPherson, 1994).

The major benefit of selenium is as an antioxidant enzyme cofactor, preventing damage to cells by oxidation. As part of the glutathione peroxidase molecule and other antioxidant selenoenzymes, selenium status plays a major role in the body’s antioxidant defence. The availability and usefulness of selenium from the diet is dependent on the form in which it is occurs. This can be either natural selenoamino acids, which are found in plants or inorganic sources like sodium selenite that are usually present in standard trace mineral premixes.

Selenomethionine, the primary form present within Sel-Plex® provides added advantages over the sodium selenite. It enables both increased availability and tissue selenium reserves that can be used quickly and effectively during increased demand. The selenium accumulated in body proteinaceous tissues when selenoamino acids are included in the diet provides an opportunity for consumers of such animal products to benefit through increased intake of selenium.

Vitamin E is the main fat-soluble antioxidant in cell membranes. It is stored in fatty tissue, liver and muscle. It can neutralise free radicals and help stop them from reacting further. In this way it acts like a protective shield around each cell, reducing tissue damage. This beneficial action of being able to slow down oxidation clearly identifies vitamin E as an important protectant for improving the quality of fresh, processed and frozen meat products. Vitamin E can stabilise the colour of red meat, but most importantly it stops fat turning rancid and helps alleviate off tastes and odours. The role and function of vitamin E become absolutely paramount when modifications are made to the fatty acid composition of the fat and lean tissue. Increasing the polyunsaturate content of the diet and hence the number of double bonds in the fat and meat substantially intensifies the susceptibility of the product to free radical attack. To fully ensure optimal benefits, animals must be fed significant amounts of vitamin E above those normally found in standard production diets. An achievable target for maximising superior product quality would be 5-6 mg vitamin E (as α-tocopherol) per kilogram of muscle tissue. It is very difficult to obtain the same effects by treating meat products during processing.


Vitapork™ ‘Choose the healthy option’

Vitapork™ is an innovative approach to enhancing the ‘healthiness’ and nutritional value of pork. It is a ‘brand’ of new lean and healthy meat that can be utilised across a range of final product formats. The object of the Vitapork™ program was to develop a new approach toward enhancing the healthiness of pork. The strategy was to increase the most important LCPUFA, EPA and DHA, and obtain the recommended n-6:n-3 ratio without compromising the physical and organoleptic properties of the carcass. Accepted understanding to date has suggested that increasing the dietary concentration of linoleic acid (C18:2) n-6, and particularly the carcass concentration, e.g. above 15% of the total fat, leads to a substantial softening of the depot fat, thereby producing carcasses with highly unacceptable processing properties which fail to satisfy consumer requirements (Whittington et al., 1986). However it is now possible to overcome this negative outcome by utilising a combination of oil products in the diet. When elevating the PUFA level, antioxidant protection becomes critical in order to provide the necessary assurance against lipid oxidation. To fulfil this need a combined selenium (Sel-Plex®) and vitamin E supplement was paramount.

The extensive amount of literature highlighting the health benefits of consuming these specific LCPUFA and the additional benefits of consuming elevated concentrations of selenium and vitamin E was one of the main reasons for developing and producing the Vitapork™ product. The need for identifying a positive way to promote and re-position pork as a healthy, nutritious product in terms of PUFA levels without compromising physical properties and organoleptic acceptability was also a significant driving force.

A series of controlled experiments and extensive field studies were undertaken to investigate various diet compositions and feeding time periods (Table 3). In association were extensive carcass assessments (Table 4). The total PUFA level in the fat tissue increased from 18% to 34% in the Vitapork™ product, which would be equivalent to the profile of good quality table margarine.


Table 3. Percentages of DHA in lean meat and fat following dietary supplementation for 2-6 weeks.




Table 4. Carcass enhancement following a 5-week supplementation period.




The Vitapork™ technology involves a diet containing very specific LCPUFA (EPA and DHA) in combination with a significant level of LA. To demonstrate the robustness of the Vitapork™ feeding protocol, three separate commercial units each having different housing facilities were used during the finishing period. In addition, three genotypes were investigated to show that the technology can be broadly utilized. All animals were weighed at the beginning and end of the supplemental period (Table 5).


Table5. Growth and carcass response following the five-week supplemental period.




The carcass produced by the Vitapork™ diet provided both an enhanced LCPUFA content and improved n-6:n-3 ratio, but equally importantly provided a very acceptable carcass in terms of processing and final product formats. The diet formulation utilises key active ingredients, such as high-DHA tuna oil, soya oil, organic selenium (Sel-Plex®) and vitamin E. The improvements from implementing the 5 weeks pre-slaughter feeding protocol are due to an increase of 300% in DHA and 68% for LA compared to standard product (Figures 2 and 3). The ability to significantly increase both carcass EPA and DHA and more specifically LA, whilst at the same time maintaining overall carcass acceptability, goes against previous knowledge regarding fatty acid enhancement of the carcass. The final product also has the added benefit of being fully traceable and checked for authenticity, meaning that the carcass can be checked and easily identified by undertaking a simple laboratory analysis.

This exciting opportunity of carcass enhancement has the ability to make pork the first choice option when purchasing meat. Vitapork™ truly delivers multi-functional meat, which provides the health conscious consumer with a high quality product containing enhanced levels of omega-3 DHA, selenium and vitamin E (Table 6).


Table 6. Characteristics of VitaporkTM.

Summary

The secret to producing good quality food is to identify the consumer’s quality criteria and act appropriately to meet them. Pig meat will need to be marketed to the consumer based on production using natural ingredients, and it will be highly beneficial if products can be traced from production through to manufacturing.

The consumer must also be able to recognise these branded meat products on the shelf and feel comfortable with the endorsement. Regaining the required image and restoring consumer trust requires a co-ordinated effort and a vision shared by all participants in the food chain including farm suppliers, service providers, farmers, meat processors, retailers and government. Information needs to flow along the chain in both directions, which can boost efficiency and allow all to benefit from the added value achieved.


Figure 2. Effect of the Vitapork™ feeding protocol on DHA content of pork (100 g portion: 92.5 g lean and 7.5 g fat).




Figure 3. Effect of the Vitapork™ feeding protocol on linoleic acid content of pork (100 g portion: 92.5 g lean and 7.5 g fat).



References

British Nutrition Foundation. 1992. Unsaturated Fatty Acids: Nutritional and Physiological Significance. Chapman and Hall, London.

Bruckner, G. 1992. In: Fatty Acids in Foods and their Health Implications. (ed. C.K. Chow), Marcel Dekker, New York, 631-646.

Burton, G.W. 1994. Vitamin E: molecular and biological function. Proc. Nutr. Soc. 53:251-262.

Emken, E.A., R.O. Aldof, R.M. Gulley. 1994. Dietary linoleic acid influences desaturation and acylation of deuterium-labelled linoleic and linolenic acids in young adult males. Biochim. Biophys. Acta 1213:277-288.

Frust, P. 1996. The role of antioxidants in nutritional support. Proc. Nutr. Soc. 55:945-961.

MacPherson, A. 1994. Selenium, vitamin E and biological oxidation. In: Recent Advances in Animal Nutrition. (P.C. Garnsworthy and D.J.A. Cole, eds) Nottingham University Press, UK. 3-30.

Pig Progress. 2001. The EU-15 and its enlargement. Elsevier International Business Information, The Netherlands. Vol. 17(9): 32-35.

Smith, C. 2003. The challenges of selling pork and pork products in a sophisticated market. World Pork Congress, Birmingham, UK.

Whittington, F.M., N.J. Prescott, J.D. Wood, M. Enser. 1986. The effect of dietary linoleic acid on the firmness of backfat in pigs of 85 kg live weight. J. Sci. Food Agric. 37:753-761.



Author: PAUL PENNY
JSR Genetics Ltd, Southburn, Driffield, United Kingdom