Tesis camote en inglés

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    ABSTRACT

    1. INTRODUCTION

    2. MATERIALS AND METHODS2.1. Place of Performance

    2.2. Raw material

    2.3. Reagents

    2.4. Equipment and materials

    2.5. Analytical Methods

    2.5.1. Determination of moisture and dry matter

    2.5.2. Anthocyanins Analysis

    2.5.2.1. Extraction and quantification of anthocyanins in alcoholic media.

    2.5.2.2. Quantification of total anthocyanins aqueous extracts.

    2.5.3. Quantification of phenolic compounds (NFs)2.5.4. Quantification of antioxidant activity (AOA)

    2.6. Experimental methodology

    2.6.1. Conditioning of the raw material

    2.6.2. Quantification of anthocyanins, total phenolics and antioxidant capacity of purple sweet

    potato peel

    2.6.3. Evaluation of the stability of the dye extracts

    2.6.3.1. Evaluation of the stability of the heat-treated extracts

    2.6.3.2. Evaluation of stability during storage extracts

    3. RESULTS AND DISCUSSION

    3.1. Quantification of total anthocyanins, total phenolic antioxidant capacity and the raw

    material

    3.1.1. Anthocyanin content

    3.1.2. Phenolic content

    3.1.3. antioxidant activity

    3.2. Evaluation of the stability of the dye extracts

    3.2.1. Influence of temperature on the stability of the extracts

    3.2.2. Evaluation of stability during storage extracts

    4. CONCLUSIONS

    5. REFERENCES

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    Anthocyanins, phenolics and antioxidant activity in three varieties of shells

    purple sweet potato(Ipomoea batatas (L.) Lam)

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    ABSTRACT

    In the present study we quantified the content of anthocyanins, phenolics and

    antioxidant activity present in the peel of three varieties of purple sweet potato: Leg Widow

    (PDV), Pachacamac (PCH) and Italian (ITA).

    The anthocyanin content (ACNS) present in the skin of three varieties of purple sweetpotato were: 1.37, 1.10 and 1.01 mg equivalent Cy-3-glu / g (bh) for the varieties PDV, PCH

    and ITA respectively. The total phenolic content (NFs) found were: 12.47, 10.99 and 12.45 mg

    chlorogenic acid equivalent / g (bh) for varieties PDV, PCH and ITA respectively. The values of

    antioxidant activity (AOA) found were: 7825, 7139.87 and 7790.90 g Trolox equivalent / g (bh)

    for varieties PDV, PCH and ITA respectively. We found a high correlation between the content

    of NFs and antioxidant activity (AOA) (r2 = 0.99) for the three varieties studied, no correlation

    was found between the content of CNRs and AOA.

    We also evaluated in concentrated aqueous extracts, stability of CNRs, NF and AOA

    facing pasteurization conditions (85 C for 15 minutes) and storage (20 C for 45 days).

    During the treatment there was an apparent pasteurization-crease and good stability for thecontent of the extracts evaluated CNRs. The content of NFs slightly declining (1-4%), being

    higher in the AOA loss (8-19%) in all extracts tested.

    During the storage was also observed an apparent increase and stability of CNRs, with

    respect to a decrease FNs (between 14-20%), being May res AOA losses (23-27%) for the

    different extracts of sweetpotato evaluated.

    I. INTRODUCTION

    As the new millennium, a new era in the field of food science and nutrition has become

    increasingly present intensity. The interaction area food - health known as the "functional

    foods". Functional foods are defined as "Any food in natural or processed, in addition topresenting its nutrient components contain additional compounds that promote health, physical

    ability and mental state of a person" (Vasconcellos, 2001).

    Currently, many of the compounds that tend to give the character functional foods have

    not been fully identified or evaluated by the physiological functions that would lead in the

    human body.

    Phenolic compounds appear as part of this wide range of functional elements and in

    recent years has given its strong relationship with the reduction of chronic diseases like cancer,

    due to its high antioxidant activity. Some of these phenolic compounds besides having the

    above properties are presented

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    as useful substances for the food industry such as in the case of the pigments called

    anthocyanins.

    In the processing industry raw materials of plant origin, there is a lot of waste that have

    not been exploited yet, by the ignorance of their functional properties and paradoxically, in the

    majority of this waste is concentrated as much these chemical elements beneficial to health,

    posing as a great potential to explore and exploit. Within the mentioned industrial waste themare sweet potato peels (including the purple), the content of phenolic compounds and good

    quality of its pigments (anthocyanins) make it a good source to consider.

    In the present research had the following objectives:

    - Quantifying total anthocyanins, total phenolics and evaluate the antioxidant capacity in

    the peel of three varieties of purple sweet potato.

    - Studying the influence of heat treatment and the storage stability of anthocyanins,

    phenolic compounds and antioxidant, in aqueous extracts of purple sweet potato peel.

    II. MATERIALS AND

    METHODS 2.1 Place of

    Performance

    This research was conducted in the laboratories of Biotechnology, Faculty of Food

    Industry and the Institute of Biotechnology (IBT) of the Universidad Nacional Agraria La Molina

    (UNALM), Industrial Biotechnology area.

    2.2 Raw material

    We used the peel of three varieties of purple sweet potato ( Ipomoea batatas (L.) lam):

    Pachacamac (PCH), Leg Widow (PDV) and Italian Purple (ITA) program provided by the roots

    and tubers of UNALM.

    2.3 Reagents

    The 37% hydrochloric acid, 96% ethanol, absolute methanol, potassium chloride,

    sodium carbonate, anhydrous sodium acetate, sodium hydroxide and potassium phosphate

    monobasic (all PA grade) were purchased from the firm MERCK. 2,2 diphenyl-1-picrylhydrazyl

    (DPPH)), 6-hydroxy-2 ,5,7,8-tetramethyl-2-carboxylic acid (Trolox), Folin-cicocalteau 2N and

    chlorogenic acid (all grade QP) were purchased from Sigma - Aldrich.

    2.4 Equipment and materials

    Magnetic stirrer (Barnstead / Thermolyne, USA) with shaking water bath (GFL,

    Germany) spectrophotometer (Genesys 5 / Milton Roy, USA), analytical balance (A & D Co.

    Ltd., Japan), potentiometer (Orion, USA) CRF (General Electric, USA), rotary evaporator

    (Buchi, Germany). Blender (Oster) and tube shaker (WORK, Hungary). Necessary materials

    were used for conducting the tests and analysis

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    2.5 Analytical Methods

    2.5.1 Determination of moisture and dry matter: Method was used gravimetric

    percentage, consisting of dry matter in a stove at 105 C for 6-9 hours until constant weight.

    The moisture content is the result of the difference of the initial and final weight expressed as a

    percentage (AOAC, 1990).

    2.5.2 Analysis of anthocyanins (ACNS)

    a. Extraction and quantification of anthocyanins in alcoholic media:

    Was performed following the method reported by Fuleki and Francis

    (1968). Anthocyanins were expressed as mg of cyanidin 3 glucosideequivalent / g of fresh product, based on a standard curve of cyanidin-3-glucoside; used the molar extinction coefficient e = 20 941 L x mol-1 xcm-1 and the molecular weight of 449.2 gx mol-1. This method was usedfor quantification of the pigments in purple sweet potato peels.

    b. Quantification of total anthocyanins in aqueous extracts: It carried

    out following the methodology reported by Wrolstad (1976). Anthocyanins

    were expressed as mg of cyanidin 3 glucoside equivalent / mL of extract,

    we used the molar extinction coefficient e = 20 941 L x mol-1 x cm-1 and

    molecular weight (MW) of 449.2 gx mol-1. This method was used for the

    stability tests of the aqueous extracts.

    2.5.3 Quantification of phenolic compounds (NF): Was performed following the

    method of Swain and Hillis (1959). Phenolic compounds were expressed as chlorogenic acid

    equivalent mg / g or ml of fresh sample extract, based on a standard curve of chlorogenic acid.

    2.5.4 Quantification of antioxidant activity (AOA): Was performed following themethod of Brand-Williams et al. (1995). The results were expressed in mg Trolox Equivalent

    / g ml fresh sample or extract, based on a standard curve of trolox.

    2.6. Experimental methodology

    2.6.1. Conditioning of the raw material

    The continued flow of operations for obtaining the potato shell shown in Figure 1.

    2.6.2. Quantification of anthocyanins, total phenolics and antioxidant capacity in

    the purple sweet potato peel

    At this stage the total anthocyanins was quantified (ACNS), total phenolics (NFs) and

    antioxidant activity (AOA) in the peel of three varieties of purple sweet potato: Leg widow

    (PDV), Pachacamac (PCH) and Italian (ITA) , using the methods described in items 2.5.2 (a),

    2.5.3 and 2.5.4. All analyzes were performed in triplicate.

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    Figure 1. Operation flow used for conditioning of raw material

    Purple SweetPotato

    Water

    WASH

    SELECTION

    BARE

    Shell

    Steam

    SCALDING

    T = 100 C,1min

    FROZEN

    T = -18 C 2

    STORAGE

    T = -18 C 2

    Water + impurities

    Sweet potatoesdamaged

    Pulp

    The results were statistically analyzed according to a completely randomized design

    (DCA) and the treatment means were confronted by the comparison test of multiple means of

    Duncan. To find the interrelation between the different characteristics evaluated, we performed

    a linear regression analysis, using the Statgraphics - PLUS 4.

    2.6.3. Evaluation of the stability of the dye extracts

    To obtain extracts of the three varieties studied (PDV, PCH and ITA) was used in

    alcohol extraction method (section 2.5.2 a). The extracts were concen-trated in vacuo at 50 C

    until a concentration of 10 Brix (aqueous extract), then the pH was adjusted to a value of 3

    0.2, using a solution of 0.1N HCl or 0.1N NaOH. Also prepared an extract of purple corn

    anthocyanins (MM) from a commercial product powder (SA Extracts and Dyes), which was

    used as reference for the evaluation of the

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    stability of purple sweet potato extracts. For evaluation of the stability of the extracts was

    performed by linear regression analysis using the Statgraphics-PLUS 4.

    a) Evaluation of the stability of the extracts subjected to heat

    treatment

    Was placed in test tubes completely sealed 3 mL of each extract (PDV, PCH,

    ITA and MM) and then subjected to heat treatment at 85 C in a water bath for

    15 minutes taking into account different intermediate times (0, 2, 5 , 10 and 15

    minutes). Immediately after each treatment the samples were placed in ice

    water at 0 C. For each time was analyzed for total anthocyanins (item 2.5.2

    b), total phenolics and antioxidant activity. Analyses were performed in

    triplicate for each of the extracts.

    b) Evaluation of stability during storage extracts

    Were placed in test tubes (capacity of 8 cm3) 3 mL of each extract (PDV, PCH,

    ITA and MM) and then be sealed. Subsequently were subjected to storage

    under the following conditions: Temperature 20 C in the presence of oxygen

    (the tubes had a headspace of 8 cm3 ) And low light, for 45 days taking into

    account different intermediate times (0, 5, 15, 30 and 45 days). For each day

    Storage Storage is analyzed for total anthocyanins (item 2.5.2 b), total

    phenolics and antioxidant activity. Analyses were performed in triplicate for

    each of the extracts.

    III. RESULTS AND DISCUSSION

    3.1. Quantification of total anthocyanins, total phenolic antioxidant capacity

    and the raw material3.1.1. Anthocyanin content

    Table 1 presents the results of anthocyanin content expressed on a dry basis and wet

    basis. There is a higher content of pigments in the range PDV (1.37 mg / g bh), representing

    20% and 26% compared to the variety PCH (1.10 mg / g bh) and ITA (1.01 mg / g bh )

    respectively.

    Box 1. Anthocyanins found in the shells of three varieties of sweet potato purple *

    P DV P CH ITA

    b. s b. h b. s b. h b. s b.h

    5 .35 1 .37 4 .56 1 .10 4 .24 1.1

    * Expressed as mg equivalent Cy-3-glucoside / g sample

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    Expressed on a dry basis (db), the pigment content is between 424 and 535 mg CNRs /

    100g. Yoshimoto et al. (1999) indicate that the outer (5mm thick) purple-fleshed sweet potato

    (variety Ayamurasaki) is 1.4 times higher anthocyanin content than the inner portion, this gives

    us an idea of the high concentration of anthocyanins in the peel. Cascon et al. (1984) mention

    that several cultivars of purple-fleshed sweetpotato obtained in different regions of Brazil

    anthocyanins vary from 100 mg to 430 mg / 100g (bs). These values correspond to the whole

    root (peel and pulp).

    Expressed on a wet basis (bh) anthocyanin content is between 101 and 137 mg of

    CNRs / 100g shell. In radishes red and white pulp shell were encountered values between 39.3

    and 185 mg CNRs / 100 g of shell, whereas the red pulp cultivars pigment content varies from

    12.2 to 52 mg CNRs / 100 g roots. They have also been reported in potato cultivars Urenika

    dwelling as a high pigment content, with an average of 183.6 and 507.8 mg CNRs / 100 g (bh)

    in pulp and peel respectively (Lewis, 1996 cited by Rodriguez-Saona et al., 1998). Rodriguez-

    Saona et al. (1998) found in red-fleshed potatoes concentrations of 28.4 mg CNRs / 100 g pulp

    and 21.7 mg / 100 g shell (bh). It is observed that the anthocyanin content found in this work is

    within the average of those obtained in other roots.

    The results of the statistical analysis indicate significant differences (a = 0.05), on the

    content of anthocyanins (bh) in the three varieties of purple sweet potato. Comparing the

    Duncan test indicated that the content of anthocyanins (bh) in the range PDV was significantly

    higher than in the PCH and ITA variety.

    3.1.2. Phenolic content

    Table 2 presents the results of the total phenolic content expressed on a dry basis and

    wet basis. One can observe a higher phenolic content in the range PDV (12.47 mg / g bh) and

    ITA (12.45 mg / g bh) that are 12% higher compared to the variety PCH (10.99 mg / g bh).

    The phenolic compound concentration expressed on a dry basis obtained in purple

    sweet potato peels are between 4.55% and 5.24%. Schmidt-Hebbel et al. (1969) reported

    values of phenolic compounds in eight varieties of apples, which is between 0.7-ban and 1.42%

    (db). Yan et al. (1999) indicate that the roots of yacon

    Table 2. Total phenolic content found in three varieties of purple sweet potato

    P DV P CH ITA

    b. s b. h b. s. b. h b. s b.h

    4 8.72 1 2.47 4 5.46 1 0.99 5 2.38 12.45

    * Expressed as mg chlorogenic acid equivalent / g sample

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    contain a substantial amount of phenolic compounds, about 3.8% (db). The latter figure would

    be closer to the values obtained from potato peels.

    Expressed on a wet basis phenolic values obtained in potato peels are between 1099

    mg and 1247mg / 100g. Walter et al. (1979) reports values of total phenolic seven potato

    cultivars (full root) which are Didos comprises between 14 and 51 mg / 100g.

    Table 3 shows the total phenolic content for different plants and compared with the

    results found in this work. It is noted that none of these

    analyzed plant exceeds those from purple sweet potato peels evaluated.

    Table 3. Comparisons of the total phenolic content of purple sweet potato peels and

    other plant products

    VegetableTotal phenolic

    VegetableTotal phenolic

    (Mg Ac. Clor / 100g) (Mg Ac. Clor / 100g)

    C amote - ITA 1237 K umara - gold * 154.4

    C amote - PCH 1084 P apa * 38.3

    C amote - PDV 1215 P apa - red skin * 41.8

    B rcoli * 8 3.1 C ebolla * 66.8

    Za nahoria * 4 0.2 L echuga - red leaf * 182.0

    C oliflor * 3 5.0 L echuga - heart * 4.24

    Umara K - shell * 7 8.5 To kill * 8.28

    *Source : Lister and Podivinsky (1998)

    Rodriguez-Saona et al. (1998) evaluated the content of phenolic acids in the peel and

    pulp of purple potatoes. Tubers peels showed a high proportion of free phenolic acids,

    especially the chlorogenic acid and p-coumaric acid.

    Phenolic acids are usually accumulated in the skin and are of much importance in the

    defense mechanisms for infection of some plants (Friend et al., 1985; Ramamurthy et al., 1992

    cited by Rodriguez-Saona et al. 1998). Yoshimoto et al. (1999) studied four varieties of sweet

    potato (flesh white, yellow, orange and purple), finding a higher concentration of phenolic

    compounds in the outer portion (5mm thick) compared to the inner portion, in all varieties. They

    also found a higher content of phenolic compounds in purple variety.

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    The results of the statistical analysis indicated that there were significant differences (a

    = 0.05) in total phenolic content (bh) in the three varieties of purple sweet potato. The

    comparison test of Duncan said phenolic content (bh) is in the range PDV as in the variety and

    ITA respective significantly higher both in the variety to PCH.

    3.1.3. Antioxidant activity

    The results of certain antioxidant activity in the peel of three varieties of purple sweet

    potato are presented in Figure 2. The variety of the PDV AOA (7825.46 mg Eq Trolox / g bh)

    was 9% and 0.4% greater with regard to the variety PCH (7139.87 mg Eq Trolox / g bh) and

    ITA (7790.90 mg Eq Trolox / g bh) respectively ; also had an AOA variety ITA 4% higher with

    respect to the variety PCH. For comparison we determined the AOA in strawberry product,

    according to the authors Wang et al., (1996) and Vinson et al., (2001), has a high antioxidant

    capacity. It can be seen that potato peel had higher antioxidant activity than the cutter.

    Cao et al. (1996) found a value calculated for antioxidant activity sweetpotato (Whole

    root) which was 5 times lower than that obtained in strawberry (Wang et al., 1996) based on 11

    times lower fresh and dry basis. Contrary to this work (see Figure 2) Strawberry (3039.31 mg

    Trolox Eq / g bh) represents 61% less compared to the variety PDV and ITA and 57% less

    compared to the variety PCH.

    Figure 2. Antioxidant activity in the peel of three varieties of purple sweet potato

    TroloxEqug/gmf

    9000

    7790.907825.46800

    0 7139.87

    7000

    6000

    5000

    4000

    3039.31

    3000

    2000

    1000

    0PDV PCH ITA Strawberry

    Variety

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    Cisneros-Cevallos (2002) mentions that the AOA-found in blueberry, plum and purple

    sweet potatoes (whole) was 1784, 3244 and 3167 mg Equiv. Trolox / g bh respectively. By

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    mentioned we can say that the purple sweet potato peels have high antioxidant activity against

    DPPH free radical?.

    The results of the statistical analysis indicated that there were significant differences (a

    = 0.05) in antioxidant activity (bh) in the three varieties of purple sweet potato. The comparison

    test indicated that the AOA Duncan (bh) is in the range PDV as in the range ITA and bothsignificantly higher than in the variety PCH.

    Finally, we looked for the relationship between the content of anthocyanins and total

    phenolic content versus antioxidant capacity to three shells of purple sweet potato varieties.

    No relationship was found between the content of anthocyanins and AOA, on the

    contrary, we found a good linear correlation between phenolic content and AOA, with r2 =

    0.998. Prior et al. (1998) analyzed four different cultivars of species Vaccinium, and found a

    linear correlation between the content slightly anthocyanin and AOA (r2 = 0.77) and a much

    higher among the phenolic content and AOA (r2 = 0.85).

    The disconnect between the content and the AOA CNRs may be due to the low ratio

    found in the relationship CNRs / NFs, the ratios found for varieties ITA, PCH and PVD were

    0.081, 0.102 and 0.113 respectively. Prior et al. (1998) found values between 0228 and 0608.

    The ratios found in the present study indicate that there is less amount of anthocyanins in

    relation to the total phenolic content, so that anthocyanins lesser influence on the amount AOA,

    this feature to be influenced mainly by the total phenolic content present in the peel of three

    varieties of sweet potato purple evaluated.

    3.2 Evaluation of the stability of the dye extracts

    Tempetatura 3.2.1 Influence on the stability of the extracts

    The effect of heat treatment (85 C x 15 minutes) in the anthocyanin content ofconcentrated extracts of purple sweet potato peel and purple corn (MM) are presented in Figure

    3. In which one can observe two phenomena: An apparent increase in concentration and high

    stability in the ACNS purple sweet potato. In extracts of PDV, PCH and ITA was observed an

    increase in color intensity to 2 minutes followed by a 15 minute stabilization up. The three

    varieties showed an increase final, being for variety and variety PCH PDV 18% and range from

    26% ITA, the GM had a 10% decrease in the anthocyanin content.

    The thermal stability of anthocyanin structure varies with pH, presence of oxygen and

    interactions with other system components. For example the methoxylation, glycosylation and

    acylation confer a protective effect against thermal degradation (Jackman and Smith, 1992).

    One of the factors that such stability should be explained first to intramolecular

    acylation or copigmentation of anthocyanins, and Francis demonstrated by Bassa

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    Figure 3. Effect of heat treatment of purple sweet potato extracts in

    CNRs stability

    R

    etention(%)

    13

    0

    12

    0

    11

    0

    10

    0

    90

    80

    7060

    50PDV

    40PCH

    30 ITA

    20MM

    10

    00 2 4 6 8 10 12 14 16

    Time(minutes)

    (1987) in sweet violet and further if these pigments is diacylated, as in the case of purple sweet

    potato anthocyanins reported by Terehara et al. (1999). The diacylation further increases the

    stability of the pigment to the monoacilacin (Rodriguez-Saona et al., 1998) diacylated

    anthocyanins are stabilized by a stacking causal sandwich hidrofficas sado by interactions

    between the aromatic residue of the acyl group and the positively charged pyrylium nucleus

    (Goto, 1987 cited by Rodriguez-Saona et al., 1998). This prevents the addition of nucleophiles,

    especially water, to the positions C-2 and C-4 of the anthocyanin pseudobases decreasing the

    formation of which would lead to degradation in pigment (Brouillard, 1981; Goto and Kondo,

    1991 referred to by Rodriguez-Saona et al., 1998).

    The effect of heat treatment (85 C) in the total phenolic content is presented in Figure

    4. It is observed that both PDV, PCH and ITA as MM, show similar behaviors and good stability.

    PDV has the highest percentage of degradation (5%) followed ITA (3%), MM (2%) and finally

    PCH (1%)

    Martinez-Valverde et al. (2000) indicate that the content of chlorogenic acid (major

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    phenolic compound) is affected by the heat treatment, a decrease was found in potato with

    respect to a raw potato 43% by microwave cooking and baking 60% in water boiling. Skrede et

    al.(2000) indicate that other thermal processes as the concentration resulting in a loss of 4% of

    phenolic pasteurized juice blueberry. Degradation of phenolic acids in purple yam extracts

    possibly led to the formation of other acids or phenolic compounds and a small percentage to

    other compounds during heat treatment (Rodriguez de Sotillo et al., 1994). These changes

    would not be discriminated against on the methodology used by the Folin-Ciocalteau method toquantify phenolic compounds derived except for some who have become reductive capacity

    and could have formed in smaller amounts.

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    Figure 4.Effect of treatment trmicode purple sweet potato extracts inNFs stability

    R

    etention(%)

    100

    90

    80

    70

    60

    50

    40

    PDV

    30

    PCH

    ITA20

    MM10

    0

    0 2 4 6 8 10 12 14 16Time(minutes)

    The effect of heat treatment on the antioxidant activity of the extracts of purple sweet

    potato 3 and GM are shown in Figure 5. A similar trend is observed in extracts of PDV and MM,

    the first to suffer the biggest drop in the AOA of 19% while for the MM was 14%.

    Figure 5. Effect of heat treatment of purple sweet potato extracts in the AOA

    100

    90

    80

    70

    (%)60

    reten

    5040

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    PDV30

    PCH20

    ITA

    10MM

    00 2 4 6 8 10 12 14

    Time(minutes)

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    From Figures 4 and 5 can be noted that given the tendency to follow the curves PDV

    varieties, PCH and ITA decreased antioxidant capacity may be linked directly with NFs

    degradation, but not so with the content of CNRs .

    3.2.2. Evaluation of stability during storage extracts

    The effect of storage on the anthocyanin content is presented in Figure 6. It can be

    seen in the purple sweet potato varieties PCH, PDV ITA and an apparent increase of pigment,

    while for the MM degradation occurred. The ACNS PDV varieties, PCH and ITA increased

    approximately until day 15 of storage, then a marked stability maintained until day 45, with a

    relative increase of anthocyanin content of 26%, 16% and 37% respectively. MM extract

    suffered a degradation of 35% to 45 days of storage.

    Figure 6. Effect of storage of purple sweet potato extracts on the stability of the CNRs

    dad

    140

    130

    120

    110

    100

    90

    (%)

    80

    retention70

    60

    PDV5040 PCH30 ITA20 MM100

    0 5 10 15 20 25 30 35 40 45 50Time (days)

    During storage there are four factors to consider: The light, oxygen, temperature and

    water action. In the case of the purple sweet potato these factors did not exert any effect due to

    the high stability of their CNRs which is attributed to its structure (intramolecular co-

    pigmentation or acylation) and interactions with other compounds (polyphenols copigmentation

    other intermolecular ). However, in the case of decreasing MM indicates the susceptibility of

    their pigment to the action of these factors together (light, temperature, oxygen and water) due

    to the simple structure posibiblemente presenting their anthocyanins (Jackman and Smith,

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    1992 ) and the small concentration of phenolic extracts compared with those obtained from

    purple sweet potato.

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    The effect of storage at ambient conditions in FNs stability is shown in Figure 7. At day

    45 NFs content for varieties PCH, PDV and ITA showed a decrease of 20%, 18% and 13%

    respectively for the MM was down 9%. The purple corn NFs are more stable to these conditions

    than those obtained from purple sweet potato.

    Figure 7. Effect of storage of purple sweet potato extracts stability in

    FNs

    Retention

    (%)

    110

    100

    90

    80

    70

    6

    0

    5

    0

    4

    0

    PDVPCH3

    0

    ITA

    20

    MM1

    0

    00 5 10 15 20 25 30 35 40 45 50

    Time(days)

    One of the main factors of degradation of NFs perhaps was the incidence of light on

    the samples. Rodriguez de Sotillo et al. (1994) studied the stability of potato extract at 4 C

    and 37 C in the dark at 25 C exposed to light for 7 days. They found no major changes in

    the extracts left in the dark, while those exposed to light showed a total degradation of its main

    phenolic component, chlorogenic acid, which apparently contributed to an increase in the

    concentration of caffeic acid.

    Oxygen could also be another factor degradation, intervening in the auto-oxidation of

    phenolic compounds. Talcott and Howard (1999) indicate that a decrease in the content of

    soluble phenolics is due to an increase in the oxygen incorporated in the samples.

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    The effect of storage on the AOA is presented in Figure 8. There isa rapid decrease in the AOA at 5 for 4 days extracts, decreasing by 20%and 22% POV PCH and ITA, while in MM only decreased by 16%. Thefour curves show a similar trend. At day 45 of storage PDV, PCH suffereda decline of 22% and ITA of 23%, while the decrease in MM was 29%.

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    Figure 8.Effect of storage of purple sweet potato extracts on the AOA

    100

    90

    80

    70

    (%)60

    retention50

    PDV

    40PCH

    30 ITA

    20MM

    10

    00 5 10 15 20 25 30 35 40 45 50

    Time (days)

    During storage there was a decline in the middle of NFs possibly by autoxidation

    (Figure 7), the oxygen in the space of "head" would be responsible for this change. The

    phenolic antioxidants act as rust as in this way, if the phenol has been oxidized loses itsantioxidant capacity (Ceballos-Casals, 2002). Photodegradation of phenol may also be involved

    in the reduction of antioxidant capacity, because during the light exposure may have been

    formed intermediates which could have caused the partial reduction of the AOA. None of the

    tests showed a stable behavior of the first order.

    IV. CONCLUSIONS

    The highest concentration of CNRs variety found in the PDV (1.37 mg Eq. Cy-3 glu /

    gm bh) followed variety PCH (1.10 mg Eq. Cy-3 glu / gm bh) and finally the variety ITA

    (1.10 mg Eq. Cy-3 glu / gm bh).

    The highest concentration of NFs are found in the variety PDV (12.47 mg Eq.

    Ac.Clorog. / Gm bh) and ITA (12.45 mg Eq. Ac.Clorog. / Gm bh) followed variety PCH

    (10.99 mg Eq. Ac . Clorog. / gm bh).

    Most AOA was found in the variety PDV (7825.46 g Eq. Trolox / gm bh) then ITA

    (7790.90 g Eq. Trolox / gm bh) and finally in the variety PCH (7139.87 g Eq. Trolox /

    gm bh). Compared with the cutter (3039.31 g Eq. Trolox / gm bh) values obtained in

    purple yam having high AOA.

    We found a high correlation between NFs and AOA (r2 = 0.998) in the three varieties of

    sweet potato purple, indicating a strong influence of NFs content in AOA. Not

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    found between CNRs and AOA.

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    During the heat treatment, the content of CNRs in PDV, PCH and ITA was increased

    (16,18 and 26% respectively), showing greater stability, whereas in the case of MM

    degradation was observed (10%) , the content of NFs suffered a slight degradation for

    both PDV, PCH, ITA (5, 1 and 3% respectively) and MM (2%), the AOA experienced a

    similar decline for PCH and ITA (8%) and even greater fall for MM (14%) and PDV

    (19%).

    During storage, the content of PDV varieties CNRs, PCH and ITA was increased (26,

    16 and 37% respectively), showing a greater stability, whereas in the case of

    degradation was observed in MM (35%), the NFs content in MM suffered less

    degradation (9%) that the PDV, PCH and ITA (20, 18 and 13% respectively), the AOA

    decreased PDV experienced (22%), PCH (22%) and ITA (23%) and higher still for MM

    (29%).

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