Comparison of Two Methods For Determining the Discoloration Potential of Potato Tubers Based on Their Chemical and Biochemical Properties (original) (raw)
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Zemdirbyste-Agriculture, 2015
The paper deals with the analysis of a ten-year study on the chemical composition of tubers of forty potato cultivars and their physiological indicators. The research was carried out at the experimental station in Parczew, Poland on a podzolic soil with typical granulometric composition of sandy silty clay, using a randomized block design in four replicates. Forty potato cultivars were the subject of this study, including eight very early, seven early, nine medium early, nine medium late and seven late cultivars. The photosynthetic activity of plants was evaluated by measuring chlorophyll a and b determined in raw leaf matter by the spectrophotometric method as well as by measurements of chlorophyll fluorescence induction of potato leaves using a fluorimeter PAM-2000. Measurements of photosynthetic indicators at various stages of potato development revealed that their increase indirectly reflected the prolongation of plant growing period, which might have a direct impact on yield quality. The chemical composition was determined by standard methods used for tubers. The main objective of the study was to determine the chemical composition of potato depending on the values of chlorophyll fluorescence indicators, which will allow prediction of the chemical composition of tubers during the growing season. The obtained results allow us to predict changes in nutrient content in potato tubers based on the indicators such as: chlorophyll a and b content, minimum and maximum fluorescence yield, maximum efficiency of photosystem in dark and mean plant growth rate.
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After-cooking darkening (ACD) phenomenon occurs when boiled or steamed potato tubers become grayish dark on exposure to air. The degree of darkening is controlled genetically and is strongly influenced by environmental factors. The pigment responsible for ACD is a complex of chlorogenic acid and iron, which is formed during cooking and oxidizes during cooling to a colored ferric di-chlorogenic acid complex. The evaluation of ACD is thus based either on the amount of chlorogenic acid in tubers (destructive method) or on the determination of the degree of color intensity on cut tuber surfaces (non-destructive method). The destructive method is HPLC based, complicated, and time consuming, particularly when a large number of samples is being evaluated. Thus, despite its deficiency, non-destructive visual examination is routinely utilized in many breeding programs. The objective of this study was to determine whether digital imaging analysis can be adapted to the evaluation of ACD. The method is based on the direct capture of the cooked and cut tuber surface image using a cooled CCD camera attached to a digital imaging system. The degree of the dark color is then measured by pixels using an imaging acquisition software. The system is calibrated at 0-255 pixel levels (0 as black, 255 as white) as standard, therefore the read values directly reflect the degree of darkening. The measurement procedure is fast, reliable, simple, and particularly applicable for handling a large number of samples. This is the first report on evaluation of ACD using a digital imaging system.
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The different potato planting dates in southern Brazil have different climatic factors that affect the yield and quality of the tubers produced. The objective of this work was to test the effect of planting date and potato cultivars on the postharvest greening of tubers. The treatments consisted of three planting dates (October, December, and February) and three potato cultivars (Agata, BRS Clara, and BRS F63 Camila). It was observed that the tubers harvested in February were less susceptible to greening, probably due to the higher physiological maturity of the tubers produced in this planting date. Tubers of cv. BRS Clara had lower greening than the tubers of the other cultivars. In addition to the light conditions, the cultivar and storage air temperature are also important factors that affect greening rates. Care must be taken with these factors to avoid losses of tubers by greening.
Photo-induced changes in quality attributes of potato tubers during storage
Journal of applied botany and food quality, 2017
The retail display of potato tubers is carried out in supermarkets under additional light sources to impart aesthetic value and consumer’s attention, however, is associated with potato greening and associated disorders. The objective of this study was to identify a most appropriate light source for potato variety ’Lady Rosetta‘ along with photo-induced changes in different quality parameters. Potato tubers were placed for 27 days at ambient storage (25 ± 2 °C) under different light sources i.e. blue, fluorescent, green, mercury and red along with dark storage, which also served as normal control. In general, quality parameters, such as sugars, chlorophyll, total glycoalkaloids, increase while attributes, such as starch and ascorbic acid decrease during the storage period. The initial increase followed by final decline has been observed in parameters, such as total phenolic contents and radical scavenging activity. The results showed maximum retention of different quality attributes ...
International Journal of Food Science and Technology, 2006
After-cooking darkening (ACD) phenomenon occurs when potato tubers develop greyish dark colour after boiling, frying, or steaming. The pigment responsible for ACD is a complex of chlorogenic acid and iron, which is formed during cooking and oxidised during cooling. The evaluation of ACD is thus based either on the amount of chlorogenic acid in raw tubers or the greyish colour intensity on cooked tuber surfaces. This study introduced a new method, the digital imaging method, for evaluation of potato ACD. The comparison of this new method with visual evaluation and the measurement of chlorogenic acid using HPLC were also presented. The digital imaging method is based on the direct measurement of the degree of dark colour on cut tuber surfaces, expressed by pixel levels. The new method is faster, more reliable and simpler when compared with any methods presently used. It is particularly applicable to handling large sample numbers.
Potato after-cooking darkening
American Journal of Potato Research, 2004
After-cooking darkening (ACD) is one of the most widespread, undesirable characteristics of cultivated potato. With the current expansion of the potato-processing industry around the world, there is a renewed interest in the development of new ways to prevent ACD. After-cooking darkening is caused by the oxidation of the ferri-chlorogenic acid in the boiled or fried potatoes. The severity of the darkening is dependent on the ratio of chlorogenic acid to citric acid concentrations in the potato tubers. Higher ratio normally results in darker tubers. The concentration of the chlorogenic and citric acids is genetically controlled and influenced by environmental conditions. This paper outlines the history of ACD and current status of knowledge of the chemistry of the dark pigment formation and its genetic and environmental determinants. Also discussed are the methods of chemical prevention of ACD presently used by the potato-processing industry and potential strategies for reducing tuber after cooking darkening using molecular approaches.
Timed Color Changes Among Raw and Baked Potato Varieties
Journal of Food Processing and Preservation, 1998
Color changes in twenty two lines of potatoes by the browning reaction were measured and evaluated by Hunter color value and National Bureau of Standard (NBS) unit of color difference (AE). me relationship between color change and total solids content was evaluated < 0.05). CO87106-5 and AC87313-3 contained the highest solids content, while CO86218-2 and CO82142-4 had the lowest solids content. Overall color change in raw potatoes by browning showed CO86142-3 with the least color change and AC87084-2 with the most. Hunter color values for the browning reaction changed with time. As time increased, potatoes became darker, redder and bluer. Moreover, all of the Hunter color values were significantly changed by baking. Color of baked BC0894-2, CO86142-3 and CO87106-5 were the least changed, while that of the baked CO80011-5, Russet Norkotah and TC1406-1 were the most changed. Degree of browning in raw potato was not correlated with total solids content, but did show a negative relationship (r =-0.12). Also, rate of color change by the browning reaction in raw potato was not related to potato total solids (r =-0.10).