THE EFFECT OF INHIBITORS ON THE AMINO ACID CONTENT IN THE STORED POTATO TUBERS

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1 ZESZYTY PROBLEMOWE POSTĘPÓW NAUK ROLNICZYCH 2008 z. 530: THE EFFECT OF INHIBITORS ON THE AMINO ACID CONTENT IN THE STORED POTATO TUBERS Honorata Danilchenko, Rima Pranaitiene, Zivile Taraseviciene, Egidija Venskutoniene Lithuanian University of Agriculture, Kaunas, Lithuania Introduction The content of amino acids in potato tubers depends mostly on the potato cultivar characteristics as well as on the growing and storing conditions [EPPENDORFER, EGGUM 1994]. Among others, the most valuable are essential amino acids: treonine, valine, methionine, isoleucine, leucine, fenilalanine, histidine, lysine, arginine. These essential amino acids available in proteins make them complete, therefore potatoes are important for protein balance in human diet. The highest amount of amino acid is in potato tuber centre [LESZCZYŃSKI 2000]. Changes in protein content occurring during storage are the effect of the amount of amino acid increase process [MIETLICKI et al. 1984]. Some authors state that during storage the amount of amino acids increases and the major part of free amino acid consists of glutamic and asparagine acids [BRIERLEY et al. 1996; CIEŚLIK, PRAZNIK 1997; YANG et al. 1999]. Some authors [CIEŚLIK, PRAZNIK 1997] claim that the increase of the amino acid content in potato tubers depends on their sprouting, whereas others [BRIERLEY et al. 1996], indicate that during storage the change of amino acids are influenced by various factors including the changes in the protein content and free amino acids. Materials and methods The research was carried out in at the Crop-Growing Product Storage and Processing Laboratory in the Department of Horticulture of Lithuanian University of Agriculture Animal Husbandry Institute of Lithuanian Veterinary Academy. To show the potato sprouting during storage, essential oils of caraway cv. Gintaras and dill cv. Grybovskij with s-carvone as the active agent were used. The ether content of caraway seeds and dill seeds was 2.23% and 2.45% respectively. For one ton of potato tubers, essential oils of caraway and dill seeds produced from 1 kg of raw material by distilling with water vapor were used. 1% water solution was made from essential oil intensely which mixed was evenly sprayed onto potato tubers. During storage potato tubers were sprayed with inhibitors twice, i.e. at the beginning of October and at the beginning of January. For comparison, the chemical inhibitor CIPC containing chloropropham, widely applied in industry, was used. The recommended amount of this inhibitor is 1 kg for 1 ton of potatoes. Potato tubers were treated with the chemical inhibitor only once, at the beginning of October. Test variants: K - untreated variant - tubers were not treated with inhibitor materials during storage; KM - tubers treated with the essential oil of caraway

2 302 H. Danilchenko et al. seeds; KR - tubers treated with the essential oil of dill seeds; C - tubers treated with the inhibitor CIPC. For the experiment the potato tubers of every variant were sacked separately by 5 kg (four replications for storage studies and four replications for studies of the quality of raw material and processed products) into polyethylene bags of 120ě thickness (in order for the essential oil not to evaporate). Potato tubers of every variant were stored for eight months (from September until May) in refrigerating cabinets of KX-_ type with automatic temperature control at 9 C (± 0.5 C) and 90-95% relative humidity. Each test variant of the examined potatoes was stored in separate cabinets. Amino acid contents were determined before and after 5 and 8 months of storage. All chemical analyses were carried out in two replications. Amino acids were disjoined by the method of ion-exchange chromatography. Data was statistically analysed using the StatSof data analysis and management module of the integrated system STATISTICA. For the evaluation of potato tuber preservation, chemical analysis and quality of processed products one- or two-factor dispersion analysis was carried out. Averages of separate variants were calculated, standard deviation, the least significant difference at the 95% probability level was estimated by using the Fisher s LSD test (P < 0.05). Results and discussion 15 amino acids were determined including 9 essential amino acids (Fig. 1). Glutamic acid and aspartic acids (asparagines) make up 33-50% of all of amino acids. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Goda Gloria Nida Vaiva Vok arginine; arginina lysine; lizyna histidine; histydyna fenilalanine; fenyloalanina tyrosine; tyrozyna leucine; leucyna isoleucine; izoleucyna methionine; metionina valine; walina alanine; alanina glycine; glicyna glutamic acid; kwas glutaminowy serine; seryna treonine; treonina aspartic acid; kwas asparaginowy Fig. 1. The amino acid content in potato tubers of different cultivars Rys. 1. Zawartość aminokwasów w bulwach ziemniaka rónych odmian Rys na końcu art Fig explonations end art.

3 THE EFFECT OF INHIBITORS ON THE AMINO ACID CONTENT The high quantity of the amides, mentioned above, resulted in a brighter colour of the processed products. It is in the agreement with ASHOOR and ZENT [1984]. Considerable quantities of leucine, valine, alanine, lysine, arginine were observed. They amounted to 4-8% of the total quantity of amino acids, whereas the observed quantities of histidine, methionine glycine were the lowest. According to the data provided by several scientists, potato tubers also contain tryptophan, however, the present studies did not detected it. As some researchers state [YANG et al. 1999], tyrosine determines pulp spottiness in potato tubers. Referring to the data of our research, the quantity of tyrosine in potato tubers of all cultivars was not high, i.e. about 2 g kg -1 of dry matter (Fig. 1). At certain storage periods, the applied inhibitors significantly limited the quantity of amino acids in potato tubers of all the analyzed cultivars (Fig. 2-11). Before storage, the quantity of amino acids in potato tubers of all cultivars was about 40% higher as compared to the quantity after 5 months of storage. After 8 months of storage the quantity of amino acids increased again. After 8 month of storage the quantity of leucine in potato tubers of cultivars Nida, Vaiva and Vokë was equal or even greater to the quantity before storage (Fig. 4-6). The share of essential amino acids is about 38-45% of all amino acids. As the component of proteins, essential amino acids make the proteins complete. Leucine and valine are the essential amino acids that prevailed in potato tubers, whereas the detected quantities of methionine and histidine were the lowest (Fig. 2-6). The alterable amino acids, asparagine and glutamine prevailed (Fig. 7-11). The latter were one of the most mobile during storage. Over the entire period of storage, the lowest change in quantities of lysine and histidine was observed in potato tubers of cultivars Goda and Nida respectively, whereas the lowest change in quantities of histidine and isoleucine was observed in potato tubers of cv. Vaiva (Fig. 2, 4 and 5). Over the entire period of storage, the lowest change in quantities of amino acids, i.e. glycine, alanine and tyrosine, was observed in potato tubers of all cultivars (Fig. 7-11). After 5 months of storage, potato tubers of the analyzed cultivars processed with dill essential oil demonstrated a significantly lower quantity of amino acids (Fig. 2-11). After 8 months of storage, potato tubers of cv. Nida processed with dill essential oil showed significantly the greatest quantity of amino acids (Fig. 4 and 9). After 8 months of storage, the greatest quantity of amino acids was demonstrated basically by potato tubers of other cultivars processed with caraway essential oil (Fig. 2-11). Literature contains no data regarding a direct influence of inhibitors on the quantity of amino acids, however, it was probably their influence on the prolongation of the rest period of potato tubers that resulted in such accumulation of amino acids in potato tubers. According to BRIERLEY et al. [1996], variation in the quantity of amino acids in potato tubers is related to their sprouting. Considerable increase in the quantity of amino acids at the end of storage was observed precisely at the moment when potato tubers of respective cultivars just started to sprout. Already sprouted potato tubers featured no substantial quantity of amino acids maybe due to the fact that a some amino acids passed to sprouts. Before the analysis of quantity of amino acids, sprouts were removed from tubers. Conclusions 1. The greatest quantity of amino acids was observed before storage in potato tubers of all cultivars.

4 304 H. Danilchenko et al. 2. After 5 months of storage potato tubers of all cultivars showed the lowest quantity of amino acids. 3. After 8 months of storage potato tubers of the analyzed cultivars processed with caraway essential oil or dill essential oil demonstrated the greatest quantity of amino acids. Literature ASHOOR S.H., ZENT J.B Maillard browning of common amino acid and sugars. J. Food Science 49: BRIERLEY E.R., BONNER P.L.R., COBB A.H Factors influencing the free amino acid content of potato (Solanum tuberosum L) tubers during prolonged storage. J. Sci. Food Agric. 70: CIEŚLIK E., PRAZNIK W Effect of harvest on the amino acid content in potato tubers. Polish J. of Food and Nutrition Sciences 1: EPPENDORFER W.H., EGGUM B.O Effects of sulphur, nitrogen, phosphorus, potassium, and water stress on dietary fiber fractions, starch, amino acids and on the biological value of potato protein. Plant Foods for Human Nutrition: 45: LESZCZYŃSKI W Jakość ziemniaka konsumpcyjnego. śywność 4(25): MIETLICKI L.W., OZIERECKOWSKA O.L., KORALEWA N.P. et al Biochimija immuniteta, pokoja, starenja rastenji. Moskwa: 263 ss. YANG J., POWERS J.R., BOYLSTON T.D., WELLER K.M Sugars and Free Amino Acids in Stored Russet Burbank potatoes Treated with CIPC and Alternative Sprout Inhibitors. J. of Food Sci. 64: Key words: amino acid, potato storage, potato tuber, sprout inhibition Summary The research was carried out in at the Crop-Growing Product Storage and Processing Laboratory, Department of Horticulture, Lithuanian University of Agriculture Animal Husbandry Institute of Lithuanian Veterinary Academy. 15 amino acids were determined in the studied samples of potato tubers of 5 cultivars including 9 essential amino acids. Essential amino acids make up 38-45% of all the amino acids. In potato tubers, the dominating amino acids were leucine and valine, the lowest amount was of methionine and histidine. Dominating alterable amino acids were glutamic and aspartic acids. The latter were one of the most mobile during the storage period. During the whole period of storage, the lowest changes were observed in the following: lysine in cv. Goda tubers, histidine in cv. Nida tubers, methionine, histidine and isoleucine in potato tubers of the cv. Vaiva. Alterable amino acids, i.e. glycine, alanine and tyrosine, during the whole period of storage changed the least in the potato tubers of all cultivars. The decrease in the protein content during the storage period causes the increase in the tyrosine content. Tyrosine is not desirable in potato tubers due to the fact that it negatively affects the color of raw potato tubers.

5 THE EFFECT OF INHIBITORS ON THE AMINO ACID CONTENT Under the increasing amount of tyrosine, potatoes darken faster. According to the data of our research, the amount of tyrosine in potato tubers of all cultivars was not significant. After carrying out the correlation analysis between the darkening of raw potato tubers and the amount of tyrosine, a weak correlation was determined (r = -0.4). WPŁYW INHIBITORÓW NA ZAWARTOŚĆ AMINOKWASÓW W BULWACH PRZECHOWYWANYCH ZIEMNIAKÓW Honorata Danilcenko, Rima Pranaitiene, Zivile Taraseviciene, Egidijavenskutoniene Litewski Uniwersytet Rolniczy, Kaunas, Litwa Słowa kluczowe: ziemniak, przechowywanie, inhibitory wzrostu, aminokwasy Streszczenie W warunkach klimatycznych Litwy ziemniaki przechowywane są zaleŝnie od kierunku uŝytkowania, od października do czerwca włącznie. Zalecana wysoka temperatura (około 8 C) przechowywania ziemniaków przeznaczonych do przetwórstwa spoŝywczego prowadzi do intensywnego kiełkowania. Od wielu lat badane są środki przeciwko kiełkowaniu mniej szkodliwe lub pochodzenia naturalnego. Zawartość aminokwasów w bulwach ziemniaków najczęściej zaleŝy od cech odmianowych, warunków uprawy i przechowywania. Celem badań było określenie wpływu inhibitorów wzrostu na zmiany ilościowe aminokwasów w czasie magazynowania ziemniaków w ciągu 8 miesięcy. W badaniach przechowalniczych przetestowano odmiany ziemniaków: Goda, Gloria, Nida, Vaiva i Vokë. Po 8 miesiącach przechowywania oznaczono w bulwach 15 aminokwasów, w tym 9 niezbędnych % sumy aminokwasów stanowiły kwas glutaminowy i asparaginowy. Najmniej wykryto histydyny, metioniny, glicyny. Tyrozyna we wszystkich bulwach badanych odmian ziemniaków występowała w nieduŝych ilościach - około 2 g kg -1 suchej substancji. Spośród niezbędnych aminokwasów decydująco większe ilości obserwowano leucyny i waliny, natomiast najmniejsze metioniny. Ilość nie niezbędnych aminokwasów: glicyny, alaniny i tyrozyny przez cały okres przechowywania zmieniała się najmniej. Stwierdzono, Ŝe naturalne inhibitory wzrostu pozytywnie wpływały na jakość przechowywanych bulw ziemniaka poprzez zmniejszenie ilości aminokwasów w ciągu 5 miesięcy przechowywania. Stosowanie naturalnych, efektywnych środków ograniczających kiełkowanie jest szansą na wyeliminowanie szkodliwych środków chemicznych stosowanych podczas przechowywania. Prof. dr Honorata Danilchenko Studentu 11, LZUU Kaunas - Akademija LITHUANIA Honorata.Danilcenko@lzuu.lt

6 Fig. 2. Changes in the quantity of essential amino acids in potato tubers of cv. Goda during storage Rys. 2. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Goda podczas przechowywania

7 Fig. 3. Changes in the quantity of essential amino acids in potato tubers of cv. Gloria during storage Rys. 3. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Gloria podczas przechowywania

8 K untreated; kontrola Fig. 4. Changes in the quantity of essential amino acids in potato tubers of cv. Nida during storage Rys. 4. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Nida podczas przechowywania

9 K untreated; kontrola Fig. 5. Changes in the quantity of essential amino acids in potato tubers of cv. Vaiva during storage Rys. 5. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Vaiva podczas przechowywania

10 K untreated; kontrola Fig. 6. Changes in the quantity of essential amino acids in potato tubers of cv. Vokë during storage

11 Rys. 6. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Vokë podczas przechowywania K untreated; kontrola Fig. 7. Changes in the quantity of essential amino acids in potato tubers of cv. Goda during storage Rys. 7. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Goda podczas przechowywania

12 K untreated; kontrola Fig. 8. Changes in the quantity of essential amino acids in potato tubers of cv. Gloria during storage Rys. 8. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Gloria podczas przechowywania

13 K untreated; kontrola Fig. 9. Changes in the quantity of essential amino acids in potato tubers of cv. Nida during storage Rys. 9. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Nida podczas przechowywania

14 K untreated; kontrola Fig. 10. Changes in the quantity of essential amino acids in potato tubers of cv. Vaiva during storage Rys. 10. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Vaiva podczas przechowywania

15 K untreated; kontrola Fig. 11. Changes in the quantity of essential amino acids in potato tubers of cv. Vokë during storage Rys. 11. Zmiany ilości niezbędnych aminokwasów w bulwach ziemniaka odmiany Vokë podczas przechowywania