Sugars and Free Amino Acids in Stored Russet Burbank Potatoes Treated with CIPC and Alternative Sprout Inhibitors

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1 JOURNAL OF FOOD SCIENCE Sugars and Free Amino Acids in Stored Russet Burbank Potatoes Treated with CIPC and Alternative Sprout Inhibitors J. Yang, J.R. Powers, T.D. Boylston, and K.M. Weller ABSTRACT Glucose, fructose, sucrose and free amino acids were measured in stored Russet Burbank potatoes treated with sprout inhibitors isopropyl-n-(3-chlorophenyl) carbamate (CIPC), 1,4-dimethylnaphthalene (DMN), cineole and salicylaldehyde. Storage effects on sugar and amino acid contents were dependent on the specific sprout inhibitor. Salicylaldehyde treatment (200 ppm) produced a rapid increase of reducing sugar content and a greater amount of free amino acids than other treatments. A smaller amount of tyrosine was found in DMN (40 ppm) treated tubers compared to all other treatments. After 16 wk at 7 C, all potatoes treated with inhibitors had mg/g dry weight reducing sugar content which would be considered acceptable for French fry processing. Key Words: potatoes, sugars, amino acids, tyrosine, sprout inhibitors INTRODUCTION SPROUTING LIMITS USEFUL POTATO STORAGE LIFE. ISOPROPYL- N-chlorophenyl carbamate (CIPC) is a widely used and effective sprout inhibitor (Liu et al., 1990). However, CIPC is one of the three pesticides most often found in the American diet, and the safety of CIPC has been a consumer concern (Gartrell et al., 1988; Barton, 1992). Several natural volatile compounds with low mammalian toxicity such as dimethylnaphthalene (DMN), monoterpenes (e.g. 1,8- cineole) and salicylaldehyde have demonstrated strong sprout-inhibiting effects (Beveridge et al., 1981; Vaughn and Spencer, 1991, 1992). DMN, cineole and salicylaldehyde are three prospective alternatives to the synthetic chemical, CIPC. Color and flavor are important sensory attributes of potato products (Lisinska and Leszcyzynski, 1990). Sugar and free amino acids are precursors of color and flavor compounds in cooked potatoes (Khanbari and Thompson, 1993; Ho and Carlin, 1989). Excessive nonenzymatic browning between amino acids and reducing sugar produces an undesirable color and unacceptable bitter taste in fried potato products (Lisinska and Leszczynski, 1990). Reducing sugars are normally the limiting factor in color development (Roe et al., 1990). Free amino acids are important in producing heterocyclic flavor compounds such as pyrazines, pyridines, oxazoles and thiazoles (Hwang et al., 1995a, b). Maga (1994) reported 45 pyrazine compounds in baked potatoes, 26 pyrazine compounds in potato chips, and 32 pyrazine compounds, 25 oxazoles, 13 pyridines and 50 thiazoles in French fries. Sensory tests reported by Powers et al. (1996) have indicated that differences could be detected between baked potatoes treated with salicylaldehyde or cineole and those treated with CIPC. It is essential to know the effects of natural sprout inhibitors on flavor precursors and sensory quality (color, flavor) of potato products. There is very little published information on the effects of sprout Authors Yang, Powers and Weller are with the Dept. of Food Science & Human Nutrition, Washington State Univ., Pullman, WA Author Boylston, formerly with Washington State Univ., is currently with the Dept. of Food Science & Human Nutrition, Iowa State Univ., Ames IA Address inquiries to Dr. J.R. Powers. inhibitors on sugars and free amino acids in potatoes. The objective of this study was to investigate sugars and free amino acids in potatoes treated with DMN, cineole and salicylaldehyde during storage. MATERIALS & METHODS Potatoes and chemical material Potatoes (Solanum tuberosum L. cv Russet Burbank) were harvested on September 27 29, 1995, in central Washington State, and stored at 7 8 C and 95% RH. Potato plants and tubers had not been treated with growth regulators or sprout inhibitors. On Feb. 5 14, 1996, potato tubers were treated with sprout inhibitors. Salicylaldehyde and 1,8-cineole were obtained from Aldrich Chemical Company Inc., (Milwaukee, WI). 1,4-dimethylnaphthalene (DMN) and 4% 1,4-dimethylnaphthalene emulsifiable concentrate (DMN-EC) were obtained from PIN/NIP Inc. (Meridian, Idaho). A 1% emulsifiable concentrate of isopropyl N-(3-chlorophenyl) carbamate (CIPC) was from Platte Chemical Company (Fremont, NE). Dabsyl chloride and amino acid standard H (no ) were purchased from Pierce (Rockford, IL). Glucose and sucrose were purchased from J.T. Baker (Phillipsburg, NJ). Fructose was from EM Science, (Gibbstown, NJ). Ribitol was from ICN Biomedical Inc. (Aurora, OH). HPLC grade acetonitrile, methanol, analytical grade ethanol, trinitrobenzenesulfonic acid, glucose and sucrose were from J.T. Baker (Phillipsburg, NJ). Inhibitor treatment Two application methods were used. Tubers were treated based on fresh weight in lots of 45 kg. For aerosol heat application, tubers were sealed in a 194 L steel drum fitted with an air inlet port at the bottom and an exit port at the top. A 50 ml side arm flask, closed with a neoprene stopper, was placed over a hot plate and connected to the air inlet port of the drum. Tygon tubing and glass capillary were used to create a closed system. When the temperature of the flask surface reached 530 C, a measured amount of sprout inhibitor (neat) was added dropwise to the flask using a syringe inserted through the stopper (Lewis et al., 1997). The flask was removed from the system and air and sprout inhibitor vapors were circulated using an aquarium pump at a flow rate of m 3 /min for 2h. After application, tubers were held at room temperature (~23 C) in the treatment containers for 16 h, and transferred to 116 L polyethylene storage containers. For spray application, a reagent atomizer was used to apply emulsified inhibitor compounds (CIPC and DMN-EC) directly to tubers at room temperature. After the surface of tubers dried, tubers were transferred to storage containers. Treated tubers and untreated control tubers in storage containers were stored at 7 C and 95% RH up to 16 wk. During storage, a vacuum pump located outside the storage room circulated ambient air through the closed containers at m 3 /min. Salicylaldehyde (200 ppm), cineole (100 ppm), DMN-1x (40 ppm) or DMN-2x (80 ppm) were applied to potatoes by aerosol heat application. DMN-EC (40 ppm) and CIPC (11 ppm) emulsifiable concentrate were applied to potatoes by spray application. The amount of inhibitors applied was based on fresh potato weight. Treatment of the potatoes was replicated once. 592 JOURNAL OF FOOD SCIENCE Volume 64, No. 4, Institute of Food Technologists

2 Sampling and extraction At 0, 2, 4, 6, 8, 16 wk after treatment, 5 tuber samples of each replication of each treatment were withdrawn at random from storage containers. The potato tubers were cut and sliced. The peel and cortex tissue excluding the 1.5 cm ends of the tubers were frozen at -20 C and freezedried. The dried tissues were milled into powders and stored at -20 C. Samples were extracted using a modified method based on that described by Picha (1985) and Hagen et al. (1993). Freeze-dried potato powder (1 g) was shaken with 25 ml of 80% ethanol using a gyrotory shaker at speed 3 (Model 5-3, New Brunswick Scientific Co., New Brunswick, NJ) at room temperature for 15 min and centrifuged at 1200 g for 10 min. The supernatant was filtered (#40 ashless) and collected, and the residue was re-extracted with 25 ml of 80% ethanol, centrifuged, and filtered. The extracts were combined, brought to 50 ml, and stored at -20 C for sugar and amino acid analysis. Based on analysis of glucose by glucose oxidase assay (Raabo and Terkildsen, 1960) and free amines by trinitrobenzenesulfonic acid assay (Habeeb, 1966), recoveries of sugars and total free amino acids in tubers using 2 extraction steps were ~89.3% and 82.7%, respectively. Sugar analysis Ribitol was added during extraction as an internal standard for sugar analyses. A 10 ml portion of the extract was concentrated to ml by nitrogen purging at 37 C. The concentrated extract was centrifuged at 16,000 g for 10 min, passed through a Millipore C18 cartridge and filtered with a syringe filter (0.45 micron). A 20 µl aliquot of concentrated extract was injected and analyzed by HPLC (Model 2350, Isco Inc., Lincoln, NE) equipped with an Aminex ion exclusion column (HPX-87, mm) (Bio-Rad, Richmond, CA) and a refractive index detector (Model HP 1040A, Waters Associates, Waldbronn, Germany). The mobile phase was isocratic sulfuric acid (0.013M) at 0.5 ml/min. The temperature of the column was kept at 35 C using a column heater (Rainin Model 1061). Sugar content was computed based on ratios of sample areas/wt of ribitol internal standard using Hewlett Packard Chemstation software. Amino acid analysis Amino acid pre-column derivatization with dabsyl chloride reagent was modified from the method of Knecht and Chang (1986). Dabsyl chloride (DABS-Cl) was dissolved in acetonitrile. A mixture containing 40 µl extract and 100 µl of 50 mm sodium bicarbonate (ph 9.0) was reacted with 200 µl of 4 nmol/µl DABS-Cl at 70 C for 15 min. The reaction was stopped by immersing the tube into ice water. After cooling, the derivatized mixture was added to 200 µl of 50 mm, ph 7.0 sodium phosphate/ethanol (1:1) and passed through a 0.45 µm syringe filter. Amino acid standards were treated by the same steps as freezedried potato powders. A recovery study using known amounts of serine, methionine, phenylalanine and tyrosine added to potato powders showed recovery was 101.5%, 90.4%, 92.1% and 97.5%, respectively. The derivatized sample (10 or 30 µl) was injected and analyzed by HPLC equipped with a gradient programmer (Model 2360, Isco Inc., Lincoln, NE), a Licrospher column (5µ, RP18, mm) (Phenomenex, Torrance, CA) and a UV/visible detector (1040A HPLC detection system, Hewlett-Packard, Waldbronn, Germany). A solvent gradient modified from the method by Jansen et al. (1991) was used. Mobile phase A consisted of 25 mmol/l sodium acetate (ph 6.5)-acetonitrile-methanol (75:15:10, v/v/v). Mobile phase B consisted of 25 mmol/l sodium acetate (ph 6.5)-acetonitrile-methanol (10:45:45, v/v/v). The gradient for mobile phase B was 0 20 min, 0 35%; min, 36 80%; min, %; min, 100%; min, 100 0%; min, 0%. The flow rate of mobile phase was at 1.0 ml/min. The column was kept at 35 C. Amino acids were measured at 460 nm. Amounts of amino acids were computed based on external standards. Experiment design and statistical analysis A 7 6 factorial treatment design was used with treatments and Table 1 Analysis of variance for sugars and amino acids Chemicals Source F Value Pr>F Glucose Treat a Time b Treat*Time Fructose Treat Time Treat*Time Sucrose Treat Time Treat*Time Total AA Treat Time Treat*Time a Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicyaldehyde (200 ppm), DMN- 1x (40 ppm), DMN -2x (80 ppm), and DMN-EC (40 ppm). b Time: at selected intervals of 0, 2, 4, 6, 8, 16 weeks after treatment with inhibitors. storage times as main factors. Two replicates of 7 treatments (6 inhibitor treatments and 1 control) were evaluated 6 times throughout the 16 wk storage period. For the sugar and free amino acid analyses of each sample, duplicate determinations were conducted on each extract. Data for control tubers at 16 wk were not collected because of excessive sprouting. The analysis of variance test for significant effects of treatment and storage time on glucose, fructose, sucrose and free amino acid contents was determined using the General Linear Model procedure (PROC GLM) in SAS. Main effect differences were considered significant at the p<0.05 level. Means separations were determined by Fisher s Least Significant (LSD) for multiple comparisons (SAS Institute, Inc. 1993). RESULTS & DISCUSSION Sprouting Control tubers started to sprout (sprouts >0.5 mm) at 4 wk storage. Tubers treated with cineole (100 ppm) started to sprout at 6 wk. Tubers treated with DMN-1x (40 ppm), DMN-EC (40 ppm) or salicylaldehyde (200 ppm) started to sprout at 8 wk. CIPC (11 ppm) and DMN-2x (80 ppm) were most effective in sprout inhibition, with a maximum sprout length of 3 mm after 16 wk. DMN at 80 ppm demonstrated the same effectiveness as CPC at 11 ppm. Van Vliet and Sparenberg (1970) reported that CIPC at ppm controlled sprouting for 6 mo at 10 C. Cineole and salicylaldehyde required a greater dosage than we used to be as effective as CIPC. Buitelaar (1987) reported treatment of tubers late in the dormancy period decreased effectiveness of sprout inhibitors. While our tubers did not have observable sprouts prior to treatment, the relatively short time (4 wk) prior to the observation of sprouts in untreated tubers suggests that earlier inhibitor treatment may have improved effectiveness. Treatment effect Interactions (p<0.05) between treatment and storage time were observed on the content of reducing sugar, sucrose and total free amino acids (Table 1). These interactions indicated that the effects of storage on sugars and amino acid profiles were dependent on the specific sprout inhibitor. Thus, the inhibitors we used may have different effects on the metabolism of carbohydrate and amino acids during storage. Khurana et al. (1985) and Daniels-Lake et al. (1996) reported that CIPC and cineole treatment resulted in different reducing sugar patterns from control tubers during storage. However, Daniels-Lake et al. (1996) exposed tubers to cineole throughout a 25 wk storage study. Sugars Reducing sugar content in treated tubers decreased from mg/g dry wt at the beginning of the treatment to mg/ g dry wt after 16 wk storage (Fig. 1). Lisiniska and Leszczynski (1990) suggested that a reducing sugar content of 12.5 mg/g (dry wt) and 25 mg/g (dry wt) in tubers was the limiting content for potato Volume 64, No. 4, 1999 JOURNAL OF FOOD SCIENCE 593

3 Sugars & Free AA in Stored Potatoes... chip and French fry processing, respectively. A greater reducing sugar content results in dark color in fried potato products (Roe et al., 1990). Based on their criterion, the reducing sugar content in all treated tubers in our study would be acceptable for French fry processing after 16 wk storage. An increase of respiration rate during tuber sprouting may be responsible for the decrease of reducing sugar at 16 wk for all treated tubers (Hughes and Fuller, 1984). Salicylaldehyde treatment resulted in elevation in reducing sugar content after treatment (Fig. 1). The rapid increase of reducing sugars could promote dark color of fried potato products. However, treated tubers normally would not be used for several wk after treatment (Van Es and Hartmans, 1987). Therefore, such an increase of reducing sugar would not be expected to cause a major problem for fried potato products. Cineole treated tubers at 4 wk had a greater reducing sugar content than others. Daniels-Lake et al. (1996) reported that continuous cineole treatment for 25 wk resulted in increased sugar contents in tubers, and caused darker fry color in potato chips than controls and CIPC treated tubers. At 16 wk, tubers treated with CIPC had larger amounts of reducing sugar (Fig. 1) than other treated tubers. Low respiration rate in CIPC treated tubers as reported by Isherwood and Burton (1975) might be responsible for the higher content of sugars in these tubers after 16 wk of storage. Sucrose content in Russet Burbank potatoes was in the range of mg/g (dry wt) during 16 wk storage (Fig.2). Leszkowiat et al. (1990) reported that sucrose, when combined with glycine in a model system, contributed to color development comparable to that of reducing sugars. They suggested that the darkening resulted from thermal hydrolysis of sucrose during frying (Shallenberger and Moore, 1957). All treatments resulted in an increase of sucrose in tubers during the first 4 wk after treatment. Salicylaldehyde treatment resulted in an early increase of sucrose content. However, when comparing sucrose content at 16 wk with that at the beginning of storage, there were no significant changes in CIPC, cineole, DMN- 1x, and DMN-2x treatments, and a decrease in salicylaldehyde and DMN-EC treatments. Total free amino acids With exception of DMN-1x treatment, total free amino acid content increased in treated tubers during the first 2 4 wk of storage (Fig. 3). The treated tubers were likely in the early stages of dormancy break based on the time period after treatment that control tubers sprouted. Brierley et al. (1996) reported a sharp increase of proteinase activity coupled with a large increase of free amino acids at emergence from dormancy. Therefore, the increase of total free amino acids we found confirmed the report by Brierley et al. (1996). Salicylaldehyde treatment resulted in a larger content of total free amino acids after 4-8 wk storage than other treatments (Fig. 3). Amides Asparagine and glutamine have been found in large amounts in tubers and made up 30 to 45% of the total amino acid content in Russet Burbank potatoes (Table 2). Ashoor and Zent (1984) ranked asparagine and glutamine as intermediate browning producing compounds in model browning systems. However, due to their large contents in potatoes, they are important in color development in fried potato tubers (Roe et al., 1990; Brierley et al., 1996). Glutamine contributes more to color development in fried potato products than asparagine (Khanbari and Thompson, 1983; Rodriguez-Saona and Wrolstad, 1997). Since tubers treated with salicylaldehyde had a larger amount of these amides after 4 8 wk storage (Fig. 4), salicylaldehyde treatment might have an effect on color quality of the fried products. About 15% of total amino acids were aspartic acid and glutamic acid (Table 2). Hwang et al. (1995a) reported that aspartic acid and glutamic acid reacted with glucose in model systems and produced large amounts of 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5methylpyrazine and 5-methyl-6,7-dihydro-5H-cyclopentapyrazine. These are key flavors in baked potatoes (Coleman and Ho, 1980; Coleman et al., 1981). Asparagine and glutamine could also produce these Fig. 2 Sucrose in treated tubers during storage at 7 C. Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicylaldehyde (200 ppm), DMN-1x (40 ppm), DMN-2x (80 ppm), DMN-EC (40 ppm). Each value represents the mean ± the standard deviation of eight analyses. Fig. 1 Reducing sugar (glucose and fructose) in treated tubers during storage at 7 C. Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicylaldehyde (200 ppm), DMN-1x (40 ppm), DMN-2x (80 ppm), DMN-EC (40 ppm). Each value represents the mean ± standard deviation of eight analyses. 594 JOURNAL OF FOOD SCIENCE Volume 64, No. 4, 1999 Fig. 3 Total free amino acids in treated tubers during storage at 7 C. Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicylaldehyde (200 ppm), DMN-1x (40 ppm), DMN-2x (80 ppm), DMN-EC (40 ppm). Each value represents the mean ± the standard deviation of eight analyses.

4 Table 2 Amino acid content ( mol/g dry wt.) in potato tubers during storage at 7 C after treatment with inhibitors*. Inhibitor Treatments control CIPC cineole salicylaldehyde DMN-1x DMN-2x DMN-EC Amino acids 0 wk 8 wk 0 wk 16 wk 0 wk 16 wk 0 w 16 wk 0 w 16 w 0 wk 16 wk 0 wk 16 wk alanine 4.10± ± ± ± ± ± ± ± ± ± ± ± ± ±1.68 arginine-proline 39.0± ± ± ± ± ± ± ± ± ± ± ± ± ±5.05 asparagine 64.2± ± ± ± ± ± ± ± ± ± ± ± ± ±19.9 aspartic acid 18.1± ± ± ± ± ± ± ± ± ± ± ± ± ±1.06 glutamine 16.1± ± ± ± ± ± ± ± ± ± ± ± ± ±2.31 glutamic acid 22.0± ± ± ± ± ± ± ± ± ± ± ± ± ±1.24 glycine 1.48± ± ± ± ± ± ± ± ± ± ± ± ± ±0.67 histidine 3.09± ± ± ± ± ± ± ± ± ± ± ± ± ±1.94 isoleucine 13.0± ± ± ± ± ± ± ± ± ± ± ± ± ±1.55 leucine 8.84± ± ± ± ± ± ± ± ± ± ± ± ± ±1.27 lysine 3.23± ± ± ± ± ± ± ± ± ± ± ± ± ±0.39 methionine 2.60± ± ± ± ± ± ± ± ± ± ± ± ± ±0.69 phenylalanine 8.79± ± ± ± ± ± ± ± ± ± ± ± ± ±1.21 serine 6.73± ± ± ± ± ± ± ± ± ± ± ± ± ±0.64 threonine 4.83± ± ± ± ± ± ± ± ± ± ± ± ± ±0.78 tyrosine 8.14± ± ± ± ± ± ± ± ± ± ± ± ± ±1.30 valine 42.2± ± ± ± ± ± ± ± ± ± ± ± ± ±3.32 *Each value represents mean ± standard deviation with eight analysis samples key pyrazines, although their yields would not be as high as from aspartic acid and glutamic acid (Hwang et al., 1995a). Thus, these four components in potatoes might influence the overall flavor properties of baked potatoes. Based on the contents of asparagine, glutamine, aspartic acid and glutamic acid in treated tubers, we calculated the amounts of key pyrazines based on the model system of Hwang et al. (1995a). Results showed that tubers treated with salicylaldehyde during 4 8 wk of storage could produce greater amounts of key pyrazines (Table 3). However, the differences in calculated key pyrazines between cineole and salicylaldehyde treatments and CIPC treatments did not account for the differences detected through sensory evaluation (Powers et al. 1996). Other differences in flavor of the baked potatoes, including the odor of cineole and salicylaldehyde on treated potatoes, may have contributed to the reported sensory results. Daniels-Lake et al. (1996) reported that cineole treated tubers had a noticeable odor during cutting and after frying in a 25 wk storage study in which tubers had been continuously exposed to cineole. We have reported that sensory thresholds of cineole, salicylaldehyde and DMN in mashed potatoes were ppm, ppm and ppm, respectively (Powers et al., 1996). In an independent study, we also found that the inhibitor residue on potatoes exceeded the determined sensory threshold through 8 wk storage for cineole treatment, 4 wk for salicylaldehyde treatment, and 2 wk for DMN treatment (unpublished data). It is likely that the low threshold of cineole resulted in the sensory differences in cineole treated tubers. Other amino acids The changes of other individual amino acid contents in tubers during storage were variable (Table 2). Ashoor and Zent (1984) reported that in model systems glycine, lysine and tyrosine were high browning producing amino acids. However, glycine, lysine and tyrosine only made up 5% of total free amino acids in our results. Therefore, these amino acids in tubers are not expected to greatly affect the sensory quality of potato products. Valine made up about 15% of total amino acid in Russet Burbank potatoes (Table 2). However, there are no reports of the contribution of valine to fry color and flavor compounds of potato products. Fig. 4 Asparagine and glutamine in treated tubers during storage at 7 C. Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicylaldehyde (200 ppm), DMN-1x (40 ppm), DMN-2x (80 ppm), DMN- EC (40 ppm). Each value represents the mean ± the standard deviation of eight analyses. Tyrosine and blackspot Free tyrosine concentration has been highly correlated with tuber blackspot susceptibility, and 4 µmol/g (dry wt) of tyrosine has been suggested to be the limiting level to the development of blackspot Volume 64, No. 4, 1999 JOURNAL OF FOOD SCIENCE 595

5 Sugars & Free AA in Stored Potatoes... Table 3 Calculated key pyrazines contributed by asparagine, gultamine, aspartic acid, and glutamic acid in baked tubers a. Relative amount b Inhibitors 2 wks 4 wks 6 wks 8 wks 16 wks control CIPC cineole salicylaldehyde DMN-1x T DMN-2x DMN-EC athe three pyrazines are 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine and 5-methyl-6,7-dihydro-5H-cyclopentapyrazine found in baked potatoes (Coleman et al., 1981). b The calculation is based on the content of asparagine, glutamine, aspartic acid and glutamic acid in stored tubers and pyrazine amounts produced in model system (Hwang et al., 1995a). (Corsini et al., 1992; Sabba and Dean, 1994). Although the tyrosine content in all treated tubers during storage were greater than 4 µmol/ g (dry wt), the DMN-1x treatment resulted in a smaller tyrosine content than other treatments at 6 8 wk (Fig. 5). The tyrosine content ( µmol/g dry wt) in DMN-1x treated tubers at 6 8 wk of storage was near the tyrosine limiting level for blackspot. Thus, DMN- 1x treatment may have an effect in promoting blackspot resistance. A study using freeze-dried tissue was conducted to compare initial browning between DMN-1x and DMN-EC treatments, which had the greatest difference of tyrosine content. However, no difference was observed in rates of browning of rehydrated freeze-dried tuber tissue between the two treatments. Also, no difference in total content of phenolic compounds was found in freeze-dried tissues between DMN-1x and DMN-EC treatments. CONCLUSIONS SPROUT INHIBITOR TREATMENTS (CIPC, DMN, CINEOLE AND salicylaldehyde) affected the contents of sugars and free amino acids in stored potatoes. The reducing sugar content in treated potatoes after 16 wk storage was acceptable for processing. Salicylaldehyde treatment (200 ppm) produced a rapid increase in reducing sugar content and a larger amount of free amino acids in potatoes. DMN (40 ppm) may have an effect in promoting tuber resistance to potato blackspot, due to small tyrosine content in DMN treated tubers. DMN treatment did not result in increases in reducing sugar or free amino acid content and is a promising alternative to CIPC as a sprout inhibitor. REFERENCES Ashoor, S.H., and Zent, J.B Maillard browning of common amino acids and sugars. J. Food Sci. 49: Fig. 5 Tyrosine in treated tubers during storage at 7 C. Treatment: control, CIPC (11 ppm), cineole (100 ppm), salicylaldehyde (200 ppm), DMN-1x (40 ppm), DMN-2x (80 ppm), DMN-EC (40 ppm). Each value represents the mean ± the standard deviation of eight analyses. Barton, K The potato skin dispute heats up. The Grower. Sept: 8. 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Potato Res. 13: Vaughn, S.F. and Spencer, G.F Volatile monoterpenes inhibit potato tuber sprouting. Am. Potato J. 68: Vaughn, S.F. and Spencer, G.F Aromatic aldehydes and alcohols as potato tuber sprout inhibitors. U.S. patent. 5,129,951. Ms received 7/28/98; revised 1/11/99; accepted 3/18/99. This research was supported by USDA-NRI grant Additional support came from SunSpiced, Inc. 596 JOURNAL OF FOOD SCIENCE Volume 64, No. 4, 1999 Reprinted from J. Food Sci. 64(4): Institute of Food Technologists