Fatôres que afetam a determinação da vitamina C na goiaba (Psidium guajava L.)

Resumo

In the present paper the authors deal with the content of ascorbic acid in guavas (Psidium guajava L.) and the methods of sampling used. Ascorbic acid was determined directly in the photoeletric colorimeter (EEL), after extraction with a 4 per cent solution of oxalic acid. Guavas from various parts of State of S.Paulo were used and the general mean found was around 100 mgm of ascorbic acid per 100 gm fresh weight of the material used for extraction. It was found that there is great variation in the ascorbic acid content according to the condition of the fruit: Ascorbic acid Condition content in Mean mgm/100 gm Green and hard 93,36 - 119,54 102,43 Small green 57,34 - 92,30 83,40 Firm ripe 71,28 - 115,98 90,32 Overripe 63,22 - 85,98 77,36 Of the diferent parts of the fruit, the skin has the highest content; the pulp between the skin and the parts containing the seeds, the "inner pulp" contains little and finallw the central parts, formed by the pulp between seeds, the "inter pulp" a engligible amount. The proportion of ascorbic acid found in the skin, inner pulp and inter pulp may be as high as 1.6: 1: 0. Furthermore, the section near the peduncule and the sepals are richer than equatorial crossections. It was proved that the amount and intensity of sun-light is at least one important factant factor determining differences in the ascorbic acid content of the fruit, which is higer in the parts which have received more light. A sharp decrease was found in the vitamin C content of ripe fruite stored in a home refrigerator. The periods of the preservation were 12-24-48-96 hours and the decrease of the ascorbic acid content m per cent was 23.4 - 42.0 - 66.8 - 76.4 of the initial content of 144.28 mgm/100 gm. The following five different methods of sampling in the determination of the amount of vitamin C were tested, with extraction in a Waring blendor: 1) whole fruit; 2,) sample taken form fruits cut into many small pieces; 3) half of a fruit divided by a crossection at equal distance from both ends; 4) half of fruit divided lenghtwise; 5) a transversal slice of about 1 cm. It was found that the two first methods geve the most reliable results.


IDocentes-livres e assistentes da Escola Superior de Agricultura "Luiz de Queiroz", de Piracicaba

IISecção de Citricultura e Frutas Tropicais, Instituto Agronômico de Campinas.

SUMMARY

In the present paper the authors deal with the content of ascorbic acid in guavas (Psidium guajava L.) and the methods of sampling used.

Ascorbic acid was determined directly in the photoeletric colorimeter (EEL), after extraction with a 4 per cent solution of oxalic acid. Guavas from various parts of State of S.Paulo were used and the general mean found was around 100 mgm of ascorbic acid per 100 gm fresh weight of the material used for extraction.

It was found that there is great variation in the ascorbic acid content according to the condition of the fruit:

Ascorbic acid

Condition content in Mean

mgm/100 gm

Green and hard 93,36 - 119,54 102,43

Small green 57,34 - 92,30 83,40

Firm ripe 71,28 - 115,98 90,32

Overripe 63,22 - 85,98 77,36

Of the diferent parts of the fruit, the skin has the highest content; the pulp between the skin and the parts containing the seeds, the "inner pulp" contains little and finallw the central parts, formed by the pulp between seeds, the "inter pulp" a engligible amount. The proportion of ascorbic acid found in the skin, inner pulp and inter pulp may be as high as 1.6: 1: 0. Furthermore, the section near the peduncule and the sepals are richer than equatorial crossections.

It was proved that the amount and intensity of sun-light is at least one important factant factor determining differences in the ascorbic acid content of the fruit, which is higer in the parts which have received more light.

A sharp decrease was found in the vitamin C content of ripe fruite stored in a home refrigerator. The periods of the preservation were 12-24-48-96 hours and the decrease of the ascorbic acid content m per cent was 23.4 - 42.0 - 66.8 - 76.4 of the initial content of 144.28 mgm/100 gm.

The following five different methods of sampling in the determination of the amount of vitamin C were tested, with extraction in a Waring blendor: 1) whole fruit; 2,) sample taken form fruits cut into many small pieces; 3) half of a fruit divided by a crossection at equal distance from both ends; 4) half of fruit divided lenghtwise; 5) a transversal slice of about 1 cm. It was found that the two first methods geve the most reliable results.

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AGRADECIMENTOS

Os autores agradecem ao Prof. F. G. Brieger e ao Dr. Silvio Moreira as valiosas sugestões recebidas durante o desenvolvimento do trabalho; ao Prof. José de Melo Morais, as facilidades oferecidas pelo seu laboratório. Pelo material gentilmente posto a nossa disposição, somos gratos à Cia. Peixe, em Posse de Ressaca; ao nosso Colega Dr. Santana, de Piracicaba, e ao Sr. Luiz Delfim, de Rio das Pedras.

LITERATURA CITADA

Entregue para publicação em 26-9-1951

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  • Fatôres que afetam a determinação da vitamina C na goiaba (Psidium guajava L.)
    J. T. A. GurgelI; J. Soubihe SobrinhoII; E. MalavoltaI; J. Leme JúniorI

Datas de Publicação

  • Publicação nesta coleção
    06 Nov 2012
  • Data do Fascículo
    1951

Histórico

  • Recebido
    26 Set 1951
Universidade de São Paulo, Escola Superior de Agricultura Av.Páduas Dias, 11, C.P 9 / Piracicaba - São Paulo, Brasil, tel. (019)3429-4486, (019)3429-4401 - Piracicaba - SP - Brazil
E-mail: scientia@esalq.usp.br