First Month Of Storage Research Articles

Biochemical changes in stored potato tubers with different rest periods

Summary Ribonuclease, desoxyribonuclease, acid phosphatase, apyrase, α-amylase, peroxidase, and phenol oxidase activities were investigated in the eyes and parenchyma of stored potato tubers of cv. Baca and Bern with different rest periods as well as effect of storage temperature and isopropyl phenycarbamates on on enzyme activity. From deep rest until sprouting a distinct increase in enzyme activity was found, especially of hydrolases. In the eyes of the tubers with shorter rest period (cv. Bern), almost all investigated enzymes were more active, particulary in the rest period. Isopropyl phenylcarbamates inhibited the increase of most enzyme activity in the external parts of the tubers and in the ageing eyes. The low storage temperature increased the activity of hydrolytic enzymes and of peroxidase during the first months of storage.

Título en español.

La chironja es una fruta cítrica cuyas características morfológicas reflejan algunas de las de la naranja dulce y otras de la toronja (pomelo). Hay gran interés en propagar esta fruta en escala comercial en Puerto Rico. Por falta de información acerca del comportamiento de la chironja bajo condiciones de almacén, se inició un estudio para avaluar la calidad de la fruta cosechada cinco y siete meses después de la fructificación. El estudio comprendió frutas de cinco clones cultivados en la Subestación Experimental de Corozal. Estas se limpiaron y se almacenaron en bolsas de polietileno a temperatura de 7° C. y a humedad relativa de 90 por 100 por un período de 70 días. Se observaron diferencias en calidad y composición química entre los cinco clones. Las frutas conservaron una buena apariencia y un buen sabor durante el período de almacenamiento de 70 días según la evaluación hecha por un panel de catadores. No obstante, los catadores prefirieron, por su sabor, las frutas almacenadas entre 25 y 55 días, independientemente de la edad al momento de la cosecha. Las diferencias en preferencia fueron significativas al 5 por 100 de probabilidad. No se encontró diferencia significativa en el sabor entre los clones. Se observó una disminución tanto en los azúcares reductores como en los azúcares totales durante el primer mes de almacenamiento de las frutas cosechadas a los cinco meses de edad en contraste con un aumento en el porcentaje de azúcares totales en las cosechadas a los siete meses de edad. En general, entre las frutas cosechadas a los siete meses, había más diferencias significativas en composición química, dependiendo de los clones, que en las cosechadas a los cinco meses. La pérdida de peso de la fruta no llegó al 1 por 100 durante todo el período de almacenamiento, independientemente de los clones o de la edad al momento de la cosecha. El patrón cromatográfico de los componentes de sabor y aroma de la cáscara de chironja fue similar para todos los clones estudiados. Se observaron concentraciones más elevadas en algunas fracciones de las frutas cosechadas a los 7 meses.

Changes in Respiratory Pathways of Potato Tuber (Solanum tuberosum L.) after Various Times of Storage of the Tuber. Comparison of Wounded and Non-Wounded Tissue

Summary Respiration of potato tuber discs increases during incubation for 1 day at 25 °C to a value which is roughly twice as high as the respiration immediately after slicing. During the storage of potato tubers the respiration level of non-incubated discs and that reached by incubated slices declines, mainly in the period from harvest to january. During the storage period the changes in activity of several parameters linked to respiration have been determined both in freshly cut slices and in incubated tissue. These parameters do not uniformly change parallel with the increase of respiration during incubation or with the decline of respiration levels during the storage period. The activity of mitochondrial malate dehydrogenase located in the matrix does not change much after wounding and incubation and decreases slowly during the storage period. Cytochrome oxidase and CN-sensitive succinate oxidase, located in the mitochondrial inner membrane slightly increase after wounding and incubation. The former rapidly decreases in activity in the first months of storage and more slowly afterwards. The latter decreases in the first months of storage and stabilizes afterwards. CN-resistant succinate oxidase activity (alternative oxidase) of the inner membrane is not present in mitochondria from non-incubated tissue. It is induced during incubation only when the potatoes have been stored for some time but is not induced immediately after harvest. Only a small activity of outer membrane located, antimycin-A resistant NADH-cytochrome c reductase could be found in freshly cut slices. During incubation it strongly increases immediately after harvest, but this increase disappears gradually during storage of the tubers. The protein content of the mitochondrial fraction roughly doubles during one day of incubation. The protein in this fraction both from fresh discs and incubated ones rises during storage of the tubers. The activity of the cytoplasmatic 6-phosphogluconate dehydrogenase doubles after incubation of discs but levels do not change throughout the storage period.

The influence of storage on antibacterial activity of sea water. I. Experiments with sea water stored at 18�C

Three sea-water samples of about 25 l each, stored at 18°C in the dark, were examined for antibacterial activity and bacterial content. Serratia marinorubra mainly was used as test bacterium. During storage for 197 to 454 days, bactericidal capacity varied considerably. In raw sea water, extreme log (N3−N0) values (N: number of colony-forming test bacteria/ml after 0 and 3 days of any test) were higher than-1 and lower than-4. Antibacterial activity of filtersterilized and autoclaved, stored, sea water likewise varied, but to a lesser degree. The number of colony-forming marine bacteria fluctuated about 3 orders of magnitude. Variations in bacterial content and in bactericidal action of stored sea water were positively correlated during the first months of storage; later, this correlation became negative. From these results it is concluded that variations in nutrient concentration — due to successive periods of growth and autolysis of marine bacteria — were the primary reason for the changes observed in antibacterial activity of stored sea-water samples.

Comparative study of 14C-labeled purified protein derivative from various mycobacteria. I. Preparation of 14C-labeled purified protein derivative antigens and their adsorption to glass.

Biologically active (14)C-labeled purified protein derivative ((14)C-PPD) has been prepared from the culture filtrates of seven species of mycobacteria, namely Mycobacterium tuberculosis Johnston strain (PPD), M. bovis BCG (PPD-BCG), M. avium (PPD-A), M. kansasii (PPD-Y), M. intracellulare (PPD-B), M. scrofulaceum (PPD-G), and M. fortuitum (PPD-F). These mycobacteria were grown in a culture medium containing a mixture of (14)C-labeled amino acids. The yield and specific radioactivity of the PPD, of the nucleic acid, of the bacterial cells, and of the CO(2) developed during growth have been determined for each of the seven species of mycobacteria. Although the yields of (14)C-PPD antigens differed greatly for the different species of mycobacteria tested, their specific radioactivities were similar. The (14)C-PPD antigens have been used as a means to measure their adsorption to glass. When glass ampoules containing dilute solutions (0.001 mg of PPD per ml) of these PPD antigens (PPD, PPD-BCG, PPD-A, PPD-Y, PPD-G, PPD-B, and PPD-F) were stored for 12 months at 5 C, it was found that they all adsorbed equally well to glass surfaces. In fact, regardless of the origin of the PPD, a loss due to adsorption of about 90% occurred during the first month of storage, and thereafter the PPD content remained practically constant for the rest of the duration of the storage period. The addition of 0.0005% Tween 80 to the PPD solutions effectively reduced the adsorption to glass of most PPD antigens. However, adsorption of PPD-BCG was not quite so effectively prevented, even when the Tween 80 concentration was increased from 0.0005 to 0.0005%.

The Effect of Maturity and Environment on Phenolic Compounds and Oxidative Browning in Carrots1,2,3

Abstract Study of influence of maturity and environmental factors showed that early seeded carrots were more prone to browning than late seeded carrots. Immature carrots were more susceptible to browning and were lower in phenols than mature carrots. Those grown in sandy soil had a higher phenolic content than those from clay soils but did not differ significantly in susceptibility to browning. Total phenols increased during storage and were highest at a storage temperature of 50 F. Susceptibility to browning increased during the first month of storage. No direct relationships were found between potential browning and total or oxidizable phenols.

Comparative Study of 14C-Labeled Purified Protein Derivative from Various Mycobacteria

Biologically active (14)C-labeled purified protein derivative ((14)C-PPD) has been prepared from the culture filtrates of seven species of mycobacteria, namely Mycobacterium tuberculosis Johnston strain (PPD), M. bovis BCG (PPD-BCG), M. avium (PPD-A), M. kansasii (PPD-Y), M. intracellulare (PPD-B), M. scrofulaceum (PPD-G), and M. fortuitum (PPD-F). These mycobacteria were grown in a culture medium containing a mixture of (14)C-labeled amino acids. The yield and specific radioactivity of the PPD, of the nucleic acid, of the bacterial cells, and of the CO(2) developed during growth have been determined for each of the seven species of mycobacteria. Although the yields of (14)C-PPD antigens differed greatly for the different species of mycobacteria tested, their specific radioactivities were similar. The (14)C-PPD antigens have been used as a means to measure their adsorption to glass. When glass ampoules containing dilute solutions (0.001 mg of PPD per ml) of these PPD antigens (PPD, PPD-BCG, PPD-A, PPD-Y, PPD-G, PPD-B, and PPD-F) were stored for 12 months at 5 C, it was found that they all adsorbed equally well to glass surfaces. In fact, regardless of the origin of the PPD, a loss due to adsorption of about 90% occurred during the first month of storage, and thereafter the PPD content remained practically constant for the rest of the duration of the storage period. The addition of 0.0005% Tween 80 to the PPD solutions effectively reduced the adsorption to glass of most PPD antigens. However, adsorption of PPD-BCG was not quite so effectively prevented, even when the Tween 80 concentration was increased from 0.0005 to 0.0005%.

The callose test for the detection of leafroll virus in potato tubers

Formation of abnormal callose in the sieve tubes is the basis of a practical test for leafroll virus infection in potato tubers. However, as it has often been stated that the test is not consistent enough, the following features were examined, with standardisation in mind: distribution of affected phloem in the tuber, detectability with different stains, the effect of the ‘Rindite’ treatment for breaking dormancy, and the effects of time and temperature of storage. In early-harvested tubers infected with leafroll virus, sieve tubes near the heel end are the most likely to contain abnormal callose but elements located in the cortex and medulla, as well as those near the cambium, can also be affected. Callose continues to form in early-harvested tubers during at least the first month of storage, but does not appear in tubers infected within a few weeks of harvest. Relatively less callose is formed at 28 C than within the range 4–18 C. The callose test may help in judging the health of a crop but it cannot be made precise enough for more critical purposes.

The Effect on Flavor of Using Substitute Fats in Dry Whole Milk

Summary Flavor deterioration in dry milks made with substitute fats was evaluated and compared with that of dry whole milk. Dried milks were prepared with cottonseed, peanut, soybean and coconut oils, and lard. All of these fats were at least partially hydrogenated with the exception of coconut oil, which was used in both hydrogenated and unhydrogenated forms. The findings of others (1, 3, 4, 9) that vacuum- or gas-packed dry whole milk develops a stale flavor, different from oxidized flavor, during early storage were confirmed. This off-flavor produced a substantial drop in the flavor score of both air- and vacuum-packed dry whole milks during the first month of storage. Such a flavor was not detected in any dry milks containing substitute fats. With the notable exception of coconut fat the substitute fats made dry milks with poor (oxidized) flavor qualities. Vacuum-packed dry milks made with coconut fat, either hydrogenated or unhydrogenated, exhibited good flavor after 6 months storage at room temperature.