Thomas J. Fitzpatrick

A comprehensive method for the determination of total potato glycoalkaloids

A method has been developed for the quantitative analysis of total glycoalkaloids (TGA) in potato tubers. The method consists of TGA extraction by suitable solvent mixtures followed by hydrolysis of the glycosides and extraction of the aglycones. The aglycones are then quantitated by nonaqueous titration. The advantages of this method over those previously described are the inclusion of glycoalkaloids that are not measured by other methods, and the simplicity, safety, and rapid nature of the procedure. This method has been applied to the TGA analysis of potato tubers subjected to a variety of storage and treatment conditions.

Potato glycoalkaloids: Increases and variations of ratios in aged slices over prolonged storage

Four commercial cultivars of potatoes were maintained under normal storage conditions at 44 F for 34 weeks. Except for a final 10 week interval tubers were withdrawn at 6 week intervals. After slicing, a portion of the slices was immediately analyzed for total glycoalkaloid content. The remaining slices were aged for four days in the dark at room temperature, then similarly analyzed.The total glycoalkaloid content of the aged slices increased dramatically on aging. This increase on aging of slices reached a maximum early in storage then decreased gradually over the storage period. In determining the individual glycoalkaloids, α-solanine and α-chaconine both increased in these slices, but the greatest increase was in the former. Appearing solely in the aged slices of the Kennebec variety, α-and β-solamarine appeared early in the storage period and gradually decreased over the storage period. Analyses of the unaged slices indicated that the glycoalkaloid content and composition of the potato tubers was little affected by storage. Aging of potato sprouts did not change their glycoalkaloid content.ResumenSe mantuvieron cuatro cultivares comerciales de papa bajo condiciones normales de almacenamiento a 44°F por 34 semanas. Con excepción del intervalo final de 10 semanas, los tubérculos se sacaron a intervalos de 6 semanas. Después de obtener discos de los tubérculos, una porción de los discos fue inmediatamente analizada para determinar el contenido de glicoalcaloides totales. El resto de los discos se envejecieron en la oscuridad, a temperatura de cuarto por cuatro días, luego se analizaron en forma similar.El contenido de glicoalcaloides totales aumentó dramáticamente en los discos envejecidos. Este aumento con la edad de los discos, alcanzó un máximo al inicio del almacenamiento, luego disminuyó gradualmente conforme avanzó el período de almacenamiento. En la determination de los glicoalcaloides individuales, α-solanina y α-chaconina aumentaron en los discos, pero el aumento más grande fue con el prirnero. Apareciendo solos en los discos envejecidos de la variedad Kennebec, α-y β-solamarina apareció al inicio del período de almacenamiento y gradualmente disminuyó durante el período de almacenamiento. Los análisis de los discos sin almacenamiento indicaron que el contenido de glicoalcaloides y la composición de los mismos en los tubéculos de papa fueron muy poco afectados por el almacenamiento. El envejecimiento de los brotes de papa no cambió su contenido de glicoalcaloides.

Commersonine, a new glycoalkaloid from two Solanum species

Abstract Selected plant introduction lines of S. chacoense and S. commersonii contain two major glycoalkaloids, demissine and a new compound called commersonine. In contrast, other plant introduction lines of S. chacoense contain only solanine and chaconine as the major glycoalkaloids. The isolation and characterization of the new glycoalkaloid is described.

Studies of the relationship of specific gravity to total solids of potatoes

SummarySpecific gravity and total solids data were studied statistically to test the absolute reliability of the relationship in American potatoes. On a limited number of samples it is strongly indicated that studies should be instituted in the United States to establish a regression curve especially suited to American varieties and growing conditions. The variation in the relationship, due to tissue air space and perhaps other causes, indicates doubt as to the absolute reliability of individual total solids values determined by means of specific gravity. This is amply demonstrated by the 95% confidence limit of ± 1.5% total solids.

Modifications of the comprehensive method for total glycoalkaloid determination

Continuing investigations and queries from workers in the field of potato research have led to minor modifications of the method for the determination of total potato glycoalkaloids (TGA) by Fitzpatrick and Osman (1). These small changes shorten the time for analysis and can possibly give improved recovery of TGA.ResumenInvestigaciones continuadas y discusiones con trabajadores en el campo de la investigatión en papa han conducido a modificaciones menores del método para la determinatión de glicoalcaloides totales de la papa (TGA) de Fitzpatrick y Osman (1). Esos cambios pequeños acortan el tiempo para análisis y posiblemente pueden dar una recuperatión mejorada de TGA.

Chemical composition of potatoes. VIII. Effect of variety, location, and year of growth on the content of nitrogen compounds

Free amino acid content, total nitrogen, extractable nitrogen, ratio of extractable to total nitrogen, solids content, and specific gravity in Cobbler, Katahdin, Kennebec, Red Pontiac, and Russet Burbank potatoes was studied. Each variety was grown in six different locations (Idaho, Maine, Pennsylvania, Wisconsin, Long Island, and the Red River Valley) during the years 1961 through 1963. The mean values for each factor, with significant differences indicated, are listed along with the high and low range, the coefficient of variation and the overall mean. The percent of total variance contributed by each of the variables and their interactions also are listed. Long Island potatoes had the highest nitrogen and amino acid content. Varietal differences were less significant. Proline was the most variable of the constituents measured. Aspartic and glutamic acids had the highest variability with respect to years grown. The effect of each variable varies from one constituent to another.ResumenSe estudió el contenido libre de amino-ácidos, el nitrógeno total, nitrógeno extractable, proporción de nitrógeno extractable y total, contenido de sólidos y gravedad específica en las varledades de papa, Cobbler, Katahdin, Kennebec, Red Pontiac y Russet Burbank. Cada variedad fue cultivada en seis diferentes localidades (Idaho, Maine, Pennsylvania, Wisconsin, Long Island y en Red River Valley) durante los años de 1961 a 1963. Los promedios para—cada factor, con diferencias significativas, se especificaron de acuerdo con la variación alta y baja, coeficiente de variación y el promedio general. El porcentaje de variación total contribuido por cada una de las variables ysus interacciones también se especificaron. Las papas de Long Island tuvieron más alto contenido de nitrógeno y amino-ácidos. La diferencia varietal fue menos significante. La prolina fue el más variable de los elementos medidos. Los ácidos aspártico y glutámico tuvieron más alta variabilidad con respecto a los años en cultivo. El efecto de cada variable varió de un componente a otro.

Changes in the sugars and amino acids in chips made from fresh, stored and reconditioned potatoes

SummaryAn investigation of the sugars and amino acids in fresh, cold stored, and reconditioned Wisconsin Kennebec potatoes showed a constant level of total nitrogen but an increasing free amino acid nitrogen from protein degradation. A constant level of free amino acid nitrogen in chips fried from these potatoes indicated an increasing formation of polymeric material. Cold storage increased the reducing sugars to 90% of the total potato sugars. At this point, chip frying caused a decrease of 88.4% of amino acid nitrogen with a corresponding decrease of 88.7% of reducing sugar. The ratio of this decrease was 1∶1.35 μmols. Acid hydrolysis indicated that part of this loss was due to reaction of amino acids with sugars. Twenty-four free amino acids and amides were identified and measured in these potatoes and in their corresponding chips.ResumenUna investigación de azúcares y amino ácidos en papas Wisconsin Kennebec frescas, almacenadas al frío y reacondicionadas ha indicado un nivel constante de nitrógeno total pero también un incremento de nitrógeno libre de amino ácidos proveniente de la decomposición de proteinas. Un nivel constante de nitrógeno libre de amino ácidos en papas fritas duras indica una creciente formación de materiales polímeros. El almacenado al frío incrementó azúcares reductores hasta a un 90% del total de los azúcares de la papa. A este punto la fritura causó un decremento de 88.4% de nitrogeno de amino ácidos con un correspondiente decremento de 88.7% de azúcares reductores. La proporción de este decremento era 1∶1.35 μmols. La hidrólisis ácida indicó que una parte de esta pérdida se debe a la reacción de los amino ácidos con los azúcares. Veinticuatro amino ácidos y ámidos han sido identificados y medidos en estas papas y en su producto frito correspondiente.

Continued studies of the relationship of specific gravity to total solids of potatoes

The reliability of specific gravity as a measure of total solids was studied statistically. Studies on an expanded number of currently popular American potato samples indicated that differences were great enough that the accepted Von Scheele regression curve now borders on the obsolete. Variations in the relationship caused by lack of uniformity in analytical techniques, as well as inherent variations in the potatoes themselves indicated that a linear regression curve based on American potato varieties is sorely needed. It is suggested that such a curve be obtained through cooperative effort sponsored by the American Potato Association.ResumenLa dependabilidad de la gravedad específica como una medida de sólidos totales ha sido estudiada estadisticamente. Estudios sobre un gran número de ejemplares de papas norteamericanas populares al presente, indicaron que las diferencias eran suficientemente grandes de tal manera que la generalmente aceptada curva d rgesión de Von Scheele es ahora casi obsoleta. Variaciones causadas por la falta de uniformidad en técnicas analíticas, como también variaciones inherentes en las papas mismas, indicaron que una curva de regresión basada sobre variedades de papas norteamericanas es muy necesaria. Se sugiere que tal curva se obtenga mediante un esfuerzo patrocinado por la American Potato Association.

Chemical composition of potatoes. III. Relationships between specific gravity and the nitrogenous constituents

SummaryKatahdin potatoes from Maine (1960 crop) were separated into high, intermediate, and low specific gravity levels immediately after harvest, then stored in the cold. Samples were withdrawn periodically for analysis. Concurrently, New York grown Katahdms were placed in cold storage and samples, when withdrawn for analysis, were separated into three specific gravity levels. The pre-separated Maine potatoes permitted more refined analytical data to be compiled. There was a progressive loss of weight during storage which was greatest in potatoes with the lowest solids content. Specific gravity changed very little during storage. The shrinkage therefore is due to a loss of solids and moisture in the ratio of the original composition. With only minor differences in the 1959 and 1960 growing seasons in Maine, there were marked differences in the composition of potatoes grown during these two seasons.

Protein, nonprotein, and total nitrogen in seedlings of potatoes

Analyses for secific gravity, total solids, total nitrogen, protein nitrogen, and nonprotein nitrogen are reported for 73 seedling samples grown in Maine, and for 10 selections grown in Idaho. The interactions between the various constituents, as indicated by regression analysis, are discussed. These samples indicate a potential for breeding a variety of potato with a higher than average protein content, but further work is necessary to determine the inheritance pattern. This work is in progress.ResumenSe reportan análisis para investigar gravedad específica, sólidos totales, nitrógeno de proteinas y nitrógeno de otros compuestos no proteínicos de 73 muestras de brotes crecidos en Maine y de 10 selecciones crecidas en Idaho. Se discuten las interacciones entre los varios constituyentes, como están indicadas por el análisis de regresión. Estas muestras indican un potencial de producir una variedad de papa con un contenido de proteina más alto que él promedio pero se necesita trabajo adicional para determinar el modo de herencia. Este trabajo está en progreso.