doi:10.5455/vetworld.2013.573-578 Flavonoids in the development of functional meat products: A review

Flavonoids or bioflavonoids are unique low molecular weight ubiquitous polyphenolic compounds produced by plants during their metabolic activities as a secondary metabolites and responsible for major organoleptic characteristics and health benefits of plant derived foods. The flavonoids are potent antioxidants agents and protect the cells by scavenging and inhibiting the production and initiation of free radicals, superoxide anions and lipid peroxy radicals. Besides potent antioxidant capacity, flavonoids also shows antimicrobial, antimutagenic, antidiabetic, antithrombosis, antirheumatic, antiatherosclerotic, antiallergic, anti-inflammatory, antiulcers and hepatoprotectives and better termed as neutraceuticals. The antioxidant capacity of meat is very low and this can be increased by adding flavonoids in meat during processing in the form of plant parts rich in flavonoids such as seeds, fruit skin or peel, bark and flower as raw or in extract form without comprising the sensory attributes of meat and meat products.


Introduction
leading to concern about the quality and shelf life of meat and meat products.The antioxidants play a major The concept of functional foods was first come in role in checking the oxidation of fat as well reducing practice in 1980s in Japan for the foods comprising the harmful free radicals just protecting the cells from certain constituents having beneficial effect on health.
damage.By improving the antioxidant capacity of The FOSHU concept (Food for Specified Health Use) meat by adding natural antioxidants such as flavonoids, came into use in 1991 in Japan for the foods which are the overall quality as well as acceptability of meat and based on knowledge of relationship between foods or meat products can be further enhanced.The meat food components and health are expected to have products prepared from low value cuts and offal have certain health benefits and have been licensed to bear poor cooking yield and emulsion stability due to higher labelling claiming that a person using them may except collagen content leads to poor emulsifying and water to obtain the health use through the consumption of binding capacity these cuts.By adding the plant based these foods.This ever increasing awareness of binders and extender, the binding as well as functional consumers about healthy foods has forced the food value of meat products increased [6].industries to develop new foods with positive health Phytochemicals such as phenolics, anthocyanins benefits [1,2].The emphasis is on adding the functional and other flavonoids prevent the occurrence of certain value to food (tertiary function), besides basic function chronic diseases in plants while maintaining the of providing nutrients (primary function) as well as freshness in fruits and prolonging the food storage and satiety of senses (secondary function).These functional these natural compounds present in plant have strong foods should have technologically developed antioxidant capacity [7].The amount of these antiingredients with specific health benefits in a significant oxidants depends upon the irradiation, plant tolerance amount of biologically active compounds which against microbes and stage of maturity of plant [8-10].influence specific beneficial function in the body.
Flavonoids are unique novel molecules possessing The nutritive value of meat is very high due to strong antioxidant capacity.Meat and meat products presence of high quality protein, vitamins, minerals are devoid of flavonoids which can be taken care of by and fat [1] and plays a pivotal role in alleviating adding the fruit, vegetables or the by-products of fruit malnutrition in developing world [3].The lack of industry.By adding these products, meat and meat inherent antioxidant and available of high quality products become rich in antioxidants and increases the nutrients leads to the problem of perishability of the value of meat.Flavonoids are the major class of ingredients meat and meat products [4,5].The inherent antito be added in food to increase the antioxidants oxidants capacity of meat products is very low activities as well as other therapeutic value of food. in plant kingdom, modulating the human metabolism alternative to chemical or synthetic antimicrobials and for prevention of chronic and degenerative diseases.
antioxidants to control the food borne diseases, inhibiting lipid oxidation and thus extending the shelf The flavonoids were first noticed by Hungarian life and quality of food products is an increasing trend scientist Albert Szent-Gyorgi in 1936 and termed as in the food industry [18].citrin or vitamin P to explain the synergy between pure Based on the source of origin, antioxidants can be vitamin C and as yet unidentified co-factors from the divided into two types viz.natural antioxidants peels of lemons [11].Till now, more than 4000 such (flavonoids) and synthetic antioxidants (BHA, BHT, âmolecules have been identified from fruits, vegetables carotene, vitamin C, vitamin E).The synthetic antiand beverages.Flavonoids are produced in plants via oxidants increase the risk of mortality in adult due to the flavonoid branch of the phenylpropanoid and rigorous toxicity and increasing risk of cancer that they acetate-malonate metabolic pathway.Flavonoids are have as compared to natural antioxidants [19].The the phenolic compounds comprising the general antioxidants activity of the flavonoids is superior to the structure of flavan nucleus phenyl benzopyrone synthetic antioxidants.The larger intake of these plants skeleton (C-3C-6C-3) in all molecules and having a in our diet further improves overall their antioxidant chromane type skeleton having phenyl substituent in capacity.The flavonoids prove better alternative to C2-C3 position.The basic structural feature of vitamin E in meat and meat products.The antioxidants flavonoid is 2-phenyl-benzo-ã-pyrane nucleus made activity is assessed by evaluating their scavenging the up of two benzene rings (A and B) linked through a capability against artificial radicals such as 2-2'heterocyclic pyran ring (C) [12].The ring synthesized azinobis-3-ethylbenzothizoline-6-sulfonic acid in polyacetate pathway whereas, B and C rings in Intake of cranberry juice at 7 mg/kg of body

Flavonoids as potent natural antioxidants
weight for two weeks to 21 men decreased the level of circulatory plasma oxidized LDH with an increase in The flavonoids exhibit the beneficial effect due to antioxidant activity [22].The intake of red wine the antioxidants and chelating properties of these phenolic extracts as well as grape polyphenols showed molecules by prevent the free radicals to damage the positive effect in reducing the blood plasma cholesterol biological molecules like lipid, protein, sugar, DNA, and triglycerides levels.This is due to the free radical RNA etc.The free radicals are having at least one free scavengering as well as metal chelating capacity of electron in their outer orbit and produced from these flavonoids.The free radical scavenging ability of ionization of oxygen such as reactive oxygen species flavonoids is due to the hydrogen donating capacity.(ROS) superoxide anion, hydroxyl and peroxyl Flavonoids also inhibit the enzymes directly linked in radicals.These radicals causes cell death by attacking the production of free radicals such as xanthine on deoxyribose and nitrogen bases, breaking the DNA oxidase, lipooxygenase and cyclooxygenase and strands and accumulation of mutations.These damage NADH oxidase, under oxidative stress and lipid the proteins by attacking sulphydryl groups and peroxidation.The presence of a hydroxyl group at disulphide bonds or by nitration of aromatic amino positions C-3 and C-3' are equally important for high acids [15][16][17].Utilization of plant extracts as an These products are reported enhance dietary fibers as and protecting the neurons and vascular endothelium well as antioxidant properties in meat product.[24].The extracts of cranberry and blueberry fruits inhibits ornithine decarboxylase expression and induce Rosemary: Rosemary is a bushy evergreen shrub quinine reductase, inhibit the proliferation of MCF-7 widely used in culinary and medicinal ingredients.The and MDA-MB 435 breast cancer cells.Quercetin antioxidant properties of rosemary extracts are very shows anti-proliferative and anticancer activities by high due to the presence of high levels of phenolic induction of apoptosis with G1 phase arrest, reduced compounds in it and the antioxidant capacity is Ras protein expression, inhibited significantly the equivalent to the BHA and BHT.These compounds are growth of MCF-7 breast adenocarcinoma, HT-29 capable of regenerating endogenous tocopherol in the human colon adenocarcinoma and K-562 human chronic phospholipid bilayer of lipoprotein [30].The rosemary myelogenous leukaemia cell line as well as HepG2 extract at 2500 ppm delays TBRAS (thiobabituric acid liver cancer cells. reacting substances) values in raw and precooked Flavonoids protect the heart and pancreas from sausage during refrigerated and frozen storage besides diseases by inhibiting LDH peroxidation and improving colour and freshness [30] and proves to a alleviating the oxidative stress.Flavonoids control the better alternative BHA and BHT.The antioxidant blood pressure by inhibiting the ACE (angiotensin activity of a number of flavonoid and flavonoid-related converting enzyme) which helps in converting phenolic acids in relation to stability of meat lipids was angiotensin I to angiotensin II.Angiotensin II is a evaluated in meat model systems over a three-week potent vasoconstrictor and limiting the conversion of storage period by and found that morin, myricetin, angiotensin I to angiotensin II by inhibiting the ACE.
kaempferol and quercetin at a level of 200 ppm were This is also complemented by preventing the nitric most active leading to TBA (2-thiobarbituric acid) oxide degradation by free radicals.Flavonoids also values of less than 0.55 ìg malondialdehyde show anti-thrombotic activity by significantly 0 equivalents/g sample after a 21-day storage at 4 C.The inhibiting the adhesion, aggregation and secretion of activity of phenolic acids belonging to the hydroxyplatelets.Hygrophila spinosa is a commonly found benzoic and caffeic acid families was moderate with a herb in India rich in flavonoids, tannins, alkaloids and 24-69% inhibition of formation of TBA reactive essential oils It is widely used in treatment of jaundice, substances.The large scale production of fruit byrenal disorders, hepatic dysfunction and inhibiting products possesses a serious problem of their disposal metastasis of cancer cells [25].Aloe vera contains and leads to environmental pollution.These fruit byphytochemicals such as flavonoids, saponins etc which products are very rich source of flavonoids and other is indication of cosmetic and medicinal value [26].
health promoting materials.By processing and Pineapple extract in ethyl acetate, methanol and water introducing newer technology, it is possible to use were found to have antioxidant capacity comparable to these fruit by-products such as skin, seed, peels etc in ascorbic acid and BHA due to presence of phenolic meat products.By adding these by-products to the meat compounds in it [27].Phytoestrogens are secondary products in a suitable amount, the quality of meat plant metabolites, structurally or functionally similar products improved significantly and the storage of to 17-ßestradiol have potentially beneficial effects as such meat products has improved.estrogen agonists or anti-estrogens in health and The incorporation of rosemary extract in disease.The major classes of phytoestrogens are isoflacooked turkey products leads to decreased lipid vones, lignans, and coumestans.Legumes especially oxidation and improved colour loss as noticed by soybeans, whole grain cereals, and some seeds are high decreased L value and increased a value during in phytoestrogen [28].

Use of flavonoids in meat and meat products
significantly reduced volatile hexanal without inducing any effects on the production of sulphur During the preparation of various meat products, volatiles in irradiated pork loins upon adding rosemary the flavonoids have been added to increase the oleoresin with tocopherol.Rosemary extracts antioxidant capacity of meat as well as to make these improved the colour of meat by reducing the met-antiviral ability [43,44].The catechins reduce the level myoglobin concentration and increasing the of peroxides even more effectively than vitamin E and th BHA in porcine lard and chicken fat [45].The addition oxymyoglobin values during 8 storage in irradiated minced beef [33].The colour of meat and meat of tea catechin at 300 ppm, significantly reduce the products is a very important factor playing an important TBRAS values of beef, duck, ostrich, pork and chicken role in marketing and consumer acceptability of these during refrigerated storage and proves to have 2-4 products.The appearance of bright red colour of times more efficient than vitamin E in different meat oxymyoglobin (bloom) of fresh meat is preferred [46].The catechins reduce the production of putrescine whereas brown or black colour is not preferred by the and tyramine in dry fermented pork sausage.The consumers.The oxidation of lipids leads to deterioaddition of green tea do not affect the pH, colour and ration in colour, flavour, texture and compromised overall senory quality of sausages [47].The nitrite is nutritional value of meat products.This lipid oxidation added during formation of meat products to get stable can be delayed or prevented by adding natural or colour, antioxidant and Antibotulinum effect.In pork synthetic antioxidants in meat and meat products.The sausage, the green tree powder have been added to synthetic antioxidants are not well accepted by the partly substitute and found the lower TBRAS value and consumers due to health concerns [34].In Asian decreased volatile basic nitrogen contents [48, 49] and countries, various natural ingredients such as herbs, in Turkish dry fermented sausage, sucuk more condiments and spices being rich source of natural efficiently than synthetic antioxidants [47].oxidants as polyphenolics, diterpenes, flavonoids, tannins Grape seed: Grape seed extract (GSE) is a by-product and phenolic acids, are increasingly added in meat and derived from the grape seeds (Vitis vinifera) that is meat products to control the lipid oxidation [35,36].Oil extracted, dried and puri?ed to produce a polyphenolic of cloves or clove oil is obtained from clove plant compound rich extract [50].Grape seed extracts (GSE) Syzygium aromaticum from bud, leaf and stem.It is has been used in meat industry to enhance the colourless and pale yellow in colour and increasingly antioxidant capacity of meat.It inhibit the oxidation being added in the meat seasoning and flavouring of products from primary lipids (lipid hydroperoxides and food products including meat products.It shows hexanal) and secondary lipids (thiobarbituric acid antibacterial and antiseptic activities against important reactive substances) [51].The grape seed extract has human pathogens [37].It has strong antioxidant been shown to improve flavour by reducing the rancid activity among all spices.The antimicro-bial activity of flavour in meat products raw beef, cooked beef, cooked spices is attributed to the phenolic compounds which pork patties, turkey, fish oil, frozen fish and grounded alter the cell membrane permeability of bacteria [38].A chicken breast and thigh meat without change in pH, significant decrease in the level of E. coli O157:H7 in yield and water activity [51-54 ].In pork, the clear cooked beef patties have been noticed with 5% olive or antioxidant effect was observed at 400 ìg/g and 0.1% apple skin extract and clove bud oil reduced the (w/w) in ground chicken to reduce the TBARS [50].pathogen by 1.6 log CFU/g [39].The shelf life of Grape seed extract at 0.1% (w/w) reduce TBRAS and chicken pickle and nuggets has been reported to hexanal in beef, chicken, turkey and raw and cooked increase by adding clove oil in these products during meat system and minor increase in the retention of red storage.
colour [54][55][56][57].The citrus industry is growing very Green tea: Green tea is a non-fermented tea.Green tea rapidly world wide.These fruits are having a is full of antioxidants to about 30% of its dry weight.
comparatively small edible part and larger inedible Green tea extract has been reported to decrease the part.Thus the production of by-products in the citrus level of carcinogenic heterocyclic amines in pan fried industry is very large.The by-products of the citrus beef and marinating the meat with green tea did not industry are full of nutritive compounds such as compromised the sensory characteristics of grilled flavonoids, polyphenols, vitamins, proteins, oil, lipids meat [40].The addition of 0.5-2% of green tea leave and minerals.Previously these by-products are very extracts have been reported to significantly decrease rarely used and disposed.This damage the fragile the levels of Clostridium perfringens in cooked ground environment and causes environmental pollution.The beef, chicken and pork during abusive cooling [41].
amount of total polyphenolic compounds are more in Green tea produced from the leaves of Camellia whole fruit than peeled fruit and in the peel than in sinensis and contains catechin flavonoids including peeled part.The outer skin/ peel/ covering of citrus catechin and epicatechin and gallic acid esters.The fruits are showing higher concentration of flavonoids.most common flavonoids in green tea is epigalloca- The flavonoid content is highest in lemon followed by techin gallate where as black tea contain more free orange and grape fruit amongst the citrus fruits.The gallic acid.Catechin is a predominant group of polymain citrus flavonoids are hysperidine, narirutin and phenols present in green tea leaves composed of four naringen.compounds epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate [42].These Recommended Dietary Allowance (RDA): The flavonoids compounds promote health by preventing lipid oxidation play major role in antioxidant system of our body due and providing antibacterial, anticarcinogenic and to the average daily intake of flavonoids ranges from (ABTS), 1-1'-diphenyl 2-picrylhydrazyl (DPPH) and shikimate pathway.The different classes of flavonoids N,N-dimethyl-p-phenylendiamine (DMPD) [20].The have been categorized based on the oxidation status of antioxidants activity is mainly due to the high central ring C. Anthocyanidins are produced by reactivity of their hydroxyl groups especially present oxidation and reduction gives rise to flavon-3-ols and on ring B towards free radicals and the flavonoids flavan-3,4-diols.Intermediate compounds such as devoid of hydroxyl groups such as flavones, flavanones, flavonols and flavones produces based on flavanones and isoflavones shows little antioxidant the presence or absence of the double bond between activities.The presence of hydroxyl group at 3 position C2-C3 molecules.results in 10 times more antioxidant capacity.The There are three major classes of flavonoids viz.double bond at C2-C3 enhances the antioxidant flavones, isoflavonoids, neoflavonoids.Flavones are activity.The antioxidant capacity of the flavonoids are derived from 2-phenyl-1,4-benzopyrene derivatives such having the following order as flavanols > flavonols > as quercetin and rutin.Isoflavanoids are derivatives of chalcones > flavones > isoflavones, except the quercetin 3-phenyl-1,4-benzopyrene where being derived from [21].neoflavanoids 4-phenyl-1,4-benzopyrene.

Table - 1
[11,assification of flavonoids and their dietary source (source:[11,13,14]) One of the common practices is to add and lipophilicity seem to play a role in protecting the vegetables, fruit, fruit by products as well extracts of lipids in membrane from lipid peroxidation and various medicinal plants into meat during preparation flavonoids protect and maintain the integrity of of meat products.The addition of bell pepper, carrot, membrane by controlling the membrane fluidity[23].grapepulpwithskin and seed, knot-cabbage, green and Flavonoids inhibit the activity of enzyme protein black tea, lemon, lotus stem etc within suitable ranges increases the quality and yield of the meat products.kinaseC(PKC) by competitive binding with the ATP at Various legumes are rich source of flavonoids beside catalytic sites on the enzyme.PKC is responsible for good source of protein, carbohydrate, vitamins and inducing the growth of tumor cells by inducing minerals.The incorporation of various legumes at mitogenesis, secretory processes, inflammatory cell suitable levels in food products including meat functions and T lymphocyte function.Protoanthocyaproducts enhances the cooking yield, emulsion nidins largely present in cranberry and blueberry fruits stability as well as functionality of these products[29].shows antitumor activities by inhibit LDH oxidation