A. Meyer, K. Suhr and P. Nielsen, Technical University of Denmark,
6.10 Commercial natural antioxidants: sources and suppliers
Table 6.5 Examples of some commercial and natural antioxidant preparations Antioxidant Some active compounds Antioxidant mechanism Comments
Tocopherol/ ; ; ; tocopherols Chain breaker, singlet From oil seeds and tocotrienol and tocotrienols oxygene quencher cereal oils. Synergists:
ascorbic and citric acids, phospholipids
Ref. 1, 2
Ascorbic Ascorbic acid and salts Chain breaker, oxygene From acerola cherries,
acid scavenger rose hips, paprika and
citrus. Ref. 1, 2 Rosemary Rosmarinic acid, Chain breaker, metal Water- or oil-soluble extracts carnosic acid, carnosol chelator preparations. Slight
taste and colour.
Synergists: ascorbic acid. Ref. 1, 3, 4 Oregano Rosmarinic acid, Chain breaker, Water- or oil-soluble extracts protocatechinic acid, metal chelator preparations. Slight
caffeic acid, tocopherols, colour and taste.
thymol, carvacrol Synergists: ascorbic
acid. Ref. 1, 3, 4, 5 Sage Rosmarinic acid, flavon Chain breaker, Slight colour and
extracts glycosides superoxide radical taste. Ref. 6
scavenger, reducer of transition metals
Green tea Catechin, epigallocatechin, Chain breaker, metal Some colour and
extracts gallic acid chelator taste. Ref. 7, 8, 9, 10
Olive Biophenols, e.g. Chain breaker From olive seeds or
extracts hydroxytyrosol, vanillic leaves.
acid, caffeic acid, Ref. 11, 12, 13, 19
oleuropein
Organic Citric, tartaric, malic acid Metal chelator From many
acids and salts vegetable sources.
Synergists:
tocopherol. Ref. 14 Phytic Phytic acid derivatives Metal chelator, chain From many seeds and
acid breaker cereals. Ref. 15
Lecithin Phospholipids, e.g. Decompose hydro- Fat- or water-dispersable phosphatidylethanolamine, peroxides, synergist preparations. Synergists phosphatidylcholine, to chain breakers, to tocopherols and phosphatidylserine metal chelator flavonoids. Ref. 16, 17 Natural -carotene, -carotene, Singlet oxygene quencher, From many fruits and carotenoids lycopene, lutein, zeaxanthin, some are chain breakers, vegetables. Often
cryptoxanthin secondary stabiliser of coloured. Ref. 11 many primary antioxidants
Natural Anthocyanins, cyanidins, Chain breaker, metal From many fruits and flavonoids quercetins, catechins chelator, radical scavenger, vegetables. Often
superoxide scavenger coloured. Ref 4, 11, 18
Notes: 1. Schuler, 1990. 2. Frankel, 1998. 3. Nakatani, 1994. 4. Larson, 1997. 5. Tisimidou et al., 1994.
6. McCarthy et al., 2000. 7. Cao et al., 1996. 8. He, 1997. 9. Manzocco et al., 2000. 10. Roedig-Penman et al., 1997. 11. Wanasundara et al., 1997. 12. Le Tutour, 1992. 13. Paiva-Martins and Gordon, 2001. 14.
Gordon, 1990. 15. Graf et al., 1984. 16. Jung et al., 1997. 17. Saito, 1997. 18. Wang et al., 1997. 19.
Uccella, 2001.
Natural food preservatives 153
6.10.1 Extracts from seeds and beans
Most unrefined plant oils are naturally protected against oxidation by a number of antioxidants, in particular the tocopherols, tocotrienols, simple phenolics, flavonols, isoflavonoids, lecithin and many others.
Most of these are lost during the refinement of the oils but can be recovered as natural antioxidants. Among these, the tocopherols are the most important.
They are often mixtures of , , , tocopherols and tocotrienols, but contain mostly and which often are more efficient antioxidants in foods at elevated temperatures than vitamin E ( -tocopherol). The tocotrienols are claimed to have a 40–60 times higher antioxidant activity compared to the tocopherols (Palm Oil Research Institute of Malaysia, private communication).
At low concentrations (100 ppm) in purified fish oil triacylglycerols, the retardation of hydroperoxides decreases in the order -tocopherol > -tocopherol > -tocopherol but the reverse order is seen at 1,000 ppm. This is due to a concentration dependence of the antioxidant capacity, showing a maximum at 100 ppm and 500 ppm for - and -tocopherols, respectively (Kulas and Ackman, 2001), while the form increase by concentration up to 1,500–2,000 ppm.
Some of the largest producers of natural tocopherols are Eisai (Japan), Henkel/Cognis (Germany), ADM (USA), Eastman Chemical (USA) and Cordia, but Daminco Inc. (USA), Jan Dekker International (the Netherlands) and Kemin Foods (USA) also produce or market natural tocopherols. Important synergists to the tocopherols are citric acid and other organic carboxylic acids, phosphoric acid and phospholipids, vitamin C, monoglycerides, alanin, cystein and rosemary extracts (e.g. Schuler, 1990).
Another important antioxidant from oil seeds is lecithin, which is a phospholipid also contributing to stabilising food emulsions and is approved as a natural emulsifier. Lecithin may complex metals, e.g. iron and copper, thereby reducing the metal-catalysed oxidation in foods. It has been shown that the high antioxidant effects of the patented antioxidant mixture consisting of ca.
8% ascorbic acid, ca. 86% lecithin and ca. 5% -tocopherol, i.e. the A/L/T system (Lo¨liger and Saucy, 1989) rests on a synergistic action involving the lecithin. Thus, in this system, lecithin not only functions as an emulsifier to keep ascorbic acid and gamma-tocopherol in close proximity, but also appears to participate in a synergistic radical exchange process between these other antioxidants (Lambelet et al., 1994). This ability of lecithin may partly explain why in some studies, lecithin protected oxidation sensible oils better than tocopherols (Jung, 2001). Producers of lecithin are the main refiners of vegetable oils, e.g. Lucas Meyer (Germany) or Riceland (USA).
Phytic acid is found in many seeds, e.g. canola, corn germ, seam, wheat and soy.
It is extracted and may be used as a food or non-food antioxidant, mainly chelating metal ions, but its strong iron-binding effects may be detrimental for food uses because of the strongly depressed iron availability for nutritional purposes.
Isoflavonoids are isolated and concentrated from the soy production in particular. The products are rich in genistein and daidzein but in foods their
antioxidant activity is not very high (Larson, 1997). However, they may have synergistic effects to other antioxidants. There are many producers of this product, e.g. Central Soya.
Furthermore, it has been claimed that extracts from oat are good antioxidants containing dihydrocaffeic acid and phospholipids and that sesame seed/sesame oil contains several active antioxidants including sesamol, sesamolin and sesamolinol (Wanasundara et al., 1997). Sesame fractions have also been claimed to be used commercially as food antioxidants but it has not been possible to identify producers. Ferulate esters from rice bran are also claimed to be efficient antioxidants protecting linoleic acid better than -tocopherol (Xu and Godber, 2001).
6.10.2 Extracts of berries and fruits, etc.
Many fruits and berries are rich in antioxidants, which are or can be extracted and concentrated. When added to foods these ingredients are able to contribute significantly to the stability of the food in question by improving the oxidation stability.
The antioxidant components are mostly vitamin C, organic acids and a large number of phenolics, e.g. the hydroxycinnamates such as caffeic acid and ferulic acid, as well as various flavonoids, some of which are strongly coloured, e.g.
anthocyanins, which are often utilised as natural food colorants. Some fruits are also very rich in carotenoids, including -carotene, which may protect against oxidation via singlet oxygen quenching as discussed in section 6.9.4.
A large number of companies produce extracts or concentrates from fruits and berries ranging from the traditional juice producers to companies that specialise in natural flavours and colours. For example, the following companies can be mentioned: Optipure (USA), Chr. Hansen (Denmark), Overseal Natural Ingredients (GB), Quim Dis (France), Inheda (France), Folexco (USA) and many of the flavour houses mentioned earlier.
Some other interesting natural antioxidants are extracts and concentrates from the acerola cherry or rose-hips, containing up to 20 g ascorbic acid per kg berry. The concentrates contain between 17% and 26% ascorbic acid, even up to 50%. These products are produced and marketed by Anidro Do Brasil, but also by Quim Dis (France). Combined with a neutralisation of the acid, this may be a strong new natural antioxidant in many foods.
Other good future candidates may be extracts of bilberries containing 25%
anthocyanidins (Optipure), prune extracts with high antioxidant score (Califor-nia Prune Board), blackcurrant extracts containing anthocyanins (Ocean Spray, USA) and extracts of cranberries, elderberries and strawberries, all strongly coloured.
Grape skin and seeds are also excellent sources of many polyphenols and the byproducts from the wine-making process are a basis for interesting commercial activities (Tomera, 1999). The antioxidants in grape products are resveratrol, quercetin, anthocyanins, cinnamates and other flavonoids. Some of the grape Natural food preservatives 155
seed extracts are claimed by the producers to possess up to 50 times stronger antioxidant activity than C or E vitamins. This type of antioxidant may be of interest when food protection, colours and a health image are wanted. Producers of grape or wine extracts are Overseal Natural Ingredients (GB), Inheda (France), Quim Dis (France), Seppic Inc (USA) and Polyphenolics (USA).
Crude olive oil, in particular extra virgin olive oil, contains 50–800 mg/kg polyphenols, in particular hydroxytyrosol, tyrosol, vanillic acid, caffeic acid and oleuropein (Visioli and Galli, 1998). These antioxidants are shown to have an equal or larger antioxidant capacity than vitamin C, vitamin E and BHT. Several olive oil producers have investigated the possibility of producing commercial natural antioxidants from olives, e.g. CreAgri Inc. (USA).
Finally, Nutrinova has developed a new food ingredient claimed to have good food antioxidant function. The product is produced from carob fruit vast and contains lignins, simple phenols and tannins.
6.10.3 Extracts from spices and herbs
Spices and herbs have been used for many centuries to enhance flavour and extend the shelf-life of various foods. More than 32 spices have been shown to behave as antioxidants in lard and in particular plants from the Lamiaceae family appear to be effective and often even more effective than BHA. Among the most effective are rosemary, marjoram, sage, oregano, basil, savoury and hyssop (Risch and Ho, 1994) as well as allspice, clove, thyme, turmeric, mace, nutmeg, ginger, cassia and cinnamon (Charalambous, 1994).
Today, rosemary, sage and oregano are exploited on a commercial scale and are produced in several forms, in particular reduced in colour and flavour and often mixed with other natural antioxidants and synergists. In fact, by extraction or molecular distillation it is often possible to isolate the antioxidant principles without any colour or flavour. They are produced to protect fats and oils, emul-sions, meat, fish, etc., in the level of 0.1% and are often found to be more efficient than synthetic antioxidants (e.g. Formanek et al., 2001; McCarthy et al., 2000).
Rosemary extracts are produced by a large number of producers of flavours and essential oils, in particular Kalsec (USA), Naturex (France), Chr. Hansen (Denmark), SKW Chemicals (Germany), Ecoms (Canada), Evesa (Spain), R.C.
Treatt (GB), Frutarom Meer (USA), Kanegrade (GB), Adrian (France) and Bush Broake Allen Ltd (GB).
Only some of the producers are offering products with reduced flavour and colour while others are sole producers of essential oils, oleoresins or chemical isolated active compounds, e.g. carvone, eugenol or thymol.
Naturex, Chr. Hansen and Kalsec produce some of the most developed natural antioxidants for food shelf-life. These companies deliver flavour- and colour-reduced products and mixes with other different natural antioxidants, e.g.
natural tocopherols, natural vitamin C, natural citric acid, natural carotenoids or other spice extracts.
Naturex produces a range of products called ‘OxyLess’, which are either water soluble or oil soluble to be used in concentrations of 0.03–0.5%.
Application examples are chicken fat, frying oils, snacks, sausages, pork, fish oil and mayonnaise and the effects are often claimed to be better than the synthetic antioxidants, e.g. BHA and BHT. The company also delivers mixed products with other natural antioxidants, flavours and colours.
Chr. Hansen produces a product range called ‘FlavorGuard’, which is also reduced in flavour and colour and combined with other natural antioxidants.
Recommended usage in foods is 0.02–0.1% based on fat content and a large number of application examples are available.
Kalsec is a third large producer of natural antioxidants for foods. ‘Herbalox’
and ‘Duralox’ are delivered in several forms and mixes, and Kalsec includes extracts from rosemary and sage as well as natural vitamin C, tocopherols and citric acid. The antioxidative effects are often claimed to be higher than the synthetic antioxidants.
The most active components in rosemary extracts are carnosic acid and carnosol (see Fig. 6.4), which is said to account for 90% of the activity but also rosmanol, epirosmanol, isorosmanol, rosmarinic acid, rosmaridiphenol, rosmadial and rosmariquinone are expected to contribute.
Oregano extracts are new on the market and are produced by the Israeli company RAD International. The product ‘Origanox’ is delivered in water-soluble or oil-water-soluble forms; the former is claimed to have strong antimicrobial activities. Flavours and colours have been reduced for food use. Just as in thyme and ginger, oregano extracted from Origanum vulgare contains thymol, carvacrol, zingerone and 6-gingerol, but also rosmarinic acid, protocatechuic acid and caffeic acid as the antioxidant principles.
The recommended usage levels for most applications are 0.01–0.2% and the product may show synergistic effects to other natural antioxidants. The products have a well-documented antioxidant effect in many foods and are claimed by the producer to be more efficient than BHA, vitamin C, tocopherols and rosemary oil (not extracts), using the Rancimat or TBA tests. The products are effective in meat, poultry, fish, oils, emulsions, flavours, soups, bakery products, dairy products, etc.
6.10.4 Tea extracts
Existing new natural antioxidants are the extracts and concentrates from green tea, which often contain 30% polyphenolics or more. Green tea antioxidants are different from other natural sources and consequently they may show interesting synergistic effects. The major antioxidants in green tea are the catechins (flavonoids), e.g. epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin gallate.
Recently, the products have been modified to meet the needs in the food industry and some producers claim a low influence on colour and taste of the foods in question and a higher antioxidant capacity compared to other natural Natural food preservatives 157
antioxidants. Tea antioxidants are typically added to 800 ppm and often mixed with tocopherols and citric acid.
The green tea antioxidants are claimed to be effective in oils, fish and emulsions. The tea catechins may be added directly to the food or to animal feeds; 200–300 mg tea catechins in chicken feed improved significantly the oxidation stability of frozen or refrigerated meat and was comparable to the same quantity of tocopherol (Tang et al., 2001) and several studies show an effective protection of pork, beef and fish after addition of tea catechins to the foods at the 300 mg/kg level (McCarthy et al., 2001; Shuze Tang et al., 2000), often with a better protection than by BHA/BHT or tocopherols.
The largest producers are Japanese or Chinese companies, e.g. Maruzen (Japan), Takeda (Japan), Sunphenon/Taiyo Kagaku (Japan), Naturex (China) but also AIM (USA), Inheda (France) and Optipure (USA).
6.10.5 Others
Antioxidative enzymes, in particular the glucose oxidase-catalase systems (see section 6.9) or L-ascorbate oxidase, are produced by most enzyme producers.
Also of interest are the strong iron complexing proteins, in particular the lactoferrins isolated from milk. By complexing iron, metal-catalysed oxidation can be reduced. Lactate-rich fractions from cheese whey do have the same effect and are claimed to have the same antioxidant capacity as BHT in shelf-life extension of pork, for example. Producers are among others DMV (the Netherlands), Armor Prote´ines (France) and Arla Foods Ingredients (Denmark).
Interesting natural antioxidants can also be found from the sea. Some sea algae and shellfishes are excellent sources of -carotene, -carotene, zeaxanthin, cryptoxanthin, astaxanthin and lutein. Producers are Henkel Corporation and Gist-Brocades. It has also been claimed that extracts from shrimp vast containing, for example, chitin/chitosan and rockfish have good antioxidant efficacy.