Title Physical, Chemical and Biological E Radiation, VI)

Size: px

Start display at page:

Download "Title Physical, Chemical and Biological E Radiation, VI)"

Candace Walters
6 years ago
Views:

of Institute for Chemi University (1965), 43(1): 60-63 Issue Date 1965-03-25 URL

1 Effect of Gamma-Ray Irradiation Title Astringeny in Kaki (Oriental Persim Physical, Chemical and Biological E Radiation, VI) Author(s) Kitagawa, Hirotoshi Citation Bulletin of Institute for Chemi University (1965), 43(1): Issue Date URL Right Type Departmental Bulletin Paper Textversion publisher Kyoto University

2 Effect of Gamma-Ray Irradiation on Removal of Astringeny in Kaki (Oriental Persimmons) * Hirotoshi KITAGAWA** Department of Pomology, Faculty of Agriculture, Kyoto University Received January 27,1965 The effect of gamma rays from Co" on removal of astringency in Kaki (Oriental persimmons) were observed. The astringency of mature Kaki fruits was removed completely by irradiation of gamma rays with dosage more than 150x 104 r. As radiation dosage increased, firmness and astringency decreased while soluble pectin increased. The fruit of which astringency removed by this treatment became soft like overripe fruit. The gamma-ray irradiation seems to accelerate ripening of fruit. From data obtained on firmness, and alcohol, acetaldehyde and water soluble pectin contents of fruit and microscopic observation of its tannin cells after irradition, it is concluded that mechanism of removal of astringency is same as in overripe fruits. INTRODUCTION It is well know that re are two types of astringency in Kaki (Oriental persimmons): astringent and non-astringent. The non-astringent type of fruit becomes non-astringent to taste as it comes to maturity on tree, while in or type fruit remains astringent until it becomes overripe. In our country astringent Kaki is generally made edible by removing its astringency using some artificial treatments. On removal of astringency of Kaki, several workers have published ir studies. Kakeshita" has reported that astringency disappears when astringent substance is polymerized by acetaldehyde formed in fruit as it matures. Kitagawaz' has observed some difference between tannin cells of both types in cell wall thickness, pit development and pectin contents, and pointed out a role of pectin in removal of astringency. He has also found interesting facts that in artificially treated fruit astringent substance remains unchanged chemically before and after such treatments and destruction of astringency is found to be due to coagulation of pectin which makes astringent substance insoluble in water. According to McArdle and Neheias3', and Miura, and Mizuta^' treatments by gamma-ray irradiation for fruits such as apples and oranges increase water soluble pectin in m. The present work has been attempted to examine furr effect of gamma-ray irradiation on removal of astringency using astringent Kaki fruit *The report on this study has also been published in Proc. Amer. Soc. Hort. Sci., 81, 213 (1061). **..IL 111 li. Ily!( ( 60 )

3 Removal of Astringeny in Kaki (Oriental Persimmons) and to clarify mechanism of removal of astringency. MATERIALS AND METHODS As samples to be examined well matured Kaki fruit of variety Hiratanenashi from our University Orchard were used. For each run of irradiation a couple of fruits were irradiated in Co" gamma-ray facility of Institute for Chemical Research, Kyoto University. The treatments were repeated three times. The dose rate in irradiation chamber was about 136 a:104r/hr when we used facility. After irradiation of fruits, firmness was first measured by a hardness meter. Then fruits were peeled and juice was extracted by a juicer. Removal of astringency was judged by tasting. The astringent substance in juice was determined by titration with 0.1 N KMnO,. alcohol, acetaldehyde and water soluble pectin contents in juice were determined using by colorimetric method", Ripper's method" and calcium pectate method", respectively. RESULTS Removal of astringency. The dosage of Co" gamma rays used for removal of astringency in Kaki fruits were 0, 1 x 104, 10 x 104, 100 x 104, 200 x 104, and 300 x 10' r. The dose of gamma radiation less than 10 x 10' r did not show any effect on astringency or on appearance of fruit. The fruits exposed to dosage more than 100 x 10' r lost astringency considerably. The ones exposed to 200 x 10' r and 300 x 10' r lost ir atringency completely, but y became soft and color became slightly dark. The effects of gamma rays observed are summarized in Table 1. With an aim to clarify mechanism of removal of astringency we observed firmness, astringency, alcohol, acetaldehyde and water soluble pectin contents of irradiated fruits exposed to gamma radiation of various values of dosage. The effects observed are given in Table 2. For comparison, date on fruits treated with alcohol and hot water are also presented in table. As radiation increased, astringency decreased. The fruit exposed to 150 x 10' r or more tastes non-astringent. Firmness of fruit decreases almost constantly as radiation dosage increases. On or hand, water soluble Table. 1. Effects of gamma radiation on removal of astringency in Kaki (Variety : Hiratanenashi). Radiation dosageastringency b judged y tasting Appearance of fruits 0 x r...quite astringent No change 1 x 10' r...quite astringent No change 10 x 10' r...quite astringent No change 100 x 10' r...slightly astringent Slightly soft 200 x 10' r...non-astringent Soft, slightly dark 300 x 10' r...non-astringent Soft, slightly dark ( 61 )

Hirotoshi Table. 2 Effects KITAGAWA of gamma radiation on firmness of Kaki (Variety: Hiratanenashi). and chemical consituents Astringency ml of 0.1 N KMnO4 Alcohol Radiation dosagefirmness x 104rkg.

4 Hirotoshi Table. 2 Effects KITAGAWA of gamma radiation on firmness of Kaki (Variety: Hiratanenashi). and chemical consituents Astringency ml of 0.1 N KMnO4 Alcohol Radiation dosagefirmness x 104rkg.titrated o, to 1 ml of juice Acetalde -Water soluble hydepectin mg of Ca-pectate mg 'O in 10 ml juice Warm water treated Alcohol treated pectin contents increases. to increase as irradiation Alcohol increases. 150 x 104 r acetaldehyde that alcohol treated with Microscopic of by astringency gamma rays Protoplasm though and alcohol from tastes and acetaldehyde It is noted contents tannin or cells that are contents show in fruit several times a tendency exposed to lower than in of removal fruit treated water. In order of 150 x 104 r were in fruit or hot observation to examine standpoint, observed of non-astringent. tannin mechanism cells of microscopically. irradiated fruits However, it do not coagulate coagulates at once even when plasmotysis of tannin cell occurs or cell is ruptured, as shown in Fig. 1. Moreover, all fruit cells are macerated by radiation and plasmoptysis occurs readily. These observations are similar to those on tannin cells of overripe fruits." Fig. 1. Tannin cells of fruit exposed to 150 x 104 r: A. Tannin cells in 0.5 N sucrose solution. The cell shows plasmolysis. B. Deplasmolysis of same cell. C. When plasmoptysis occursed protoplasm coagulates instantly. Dyed with ferric chloride. ( 62 )

5 Removal of Astringeny in Kaki (Oriental Persimmons) DISCUSSION The gamma radiation of more than 150 x 104 r removed astringency from astringent Kaki fruit, but irradiated fruit became soft like overripe fruit. As radiation dosage increased firmness of fruit decreased and water soluble pectin contents increased. These changes were similar to those observed by McArdle and Neheias" with apples and carrots. They concluded that se changes were due to depolymerization of pectic substance by gamma-ray irradiation. It is well know that ethylene promote fruit ripening. This fact has been known to be due to depolymerization of pectic substance." Overholser" has reported that exposure of Kaki fruits to dilute concentrations of ethylene and its derivatives for periods of 15 to 25 hours results in a more rapid loss of astringency than for check specimens. The treated fruit, however, tended to soften so rapidly that he concluded this method for removal of astringency being of value only in preparation for local markets. He did not determine changes in pectin in fruit, nor did he observe tannin cells involved microscopically. It seems that gamma rays and ethylene have a similar effect to ripen fruit rapidly. From se facts mentioned above, as a practical method for removal of astringency gamma radiation is not very favorable unless any method can be found to keep irradiated fruit firm. In astrigent Kaki removal of astringency by artificial treatment is due to coagulation of protoplasm in its tannin cells." It is also known that when astringent fruit becomes overripe water soluble pectin increases." Taking into consideration data obtained on firmness, alcohol, acetaldehyde and water soluble pectin contents, mechanism of removal of astringency by gamma-ray irradiation seems to be different from or artficially treated fruits but is same as in overripe fruits. This was also co-nfirmed by microscopic observation. ACKNOWLEDGMENT The author wishes to expess his appreciation to Professor A. Kobayashi of Kyoto University and Dr. Clore of Washington State University for ir valuable advice in writing this paper. He is also indebted to Mr. R. Katano, Institute for Chemical Research, Kyoto University, for his kind co-operation with irradiation of gamma rays. REFERENCES (1) A. Kakeshita, Proc. Imp. Acad. of Japan, 6, 397 (1930). (2) Fl. Kitagawa, Ph.D. sis, Faculty of Agriculture, Kyoto University, (3) F.J. McArdle and J.K. Neheias, Food Technol., 10, 599 (1956). (1) H. Miura and T. Mizuta, Journ. Jap. Soc. Hort. Sci., 31, 17 (1962). (5) I. Tanabe, `Hakkogalcu Kenkyu-ho", Vol. 10, Kawade Shobo, Takyo, 1951, in Japanese. (6) M.H. Carre and D. Haynes, Biochem. Journ., 16, 60 (1962). (7) R.M. Smock and A.M. Neubert "Apples and Apple Products", Interscience Publishers, New York, (8) E.L. Overholser, Proc. Amer. Soc. Hort. Sci., 24, 256 (1927). ( 63 )

The Climacteric Rise in Respiration Rate of the Fuerte Avocado Fruit

Proceedings of the AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE 1941 39:137-142 The Climacteric Rise in Respiration Rate of the Fuerte Avocado Fruit By J. B. BIALE, University of California, Los Angeles,