PHYSICAL, PHYSIOLOGICAL AND CHEMICAL CHANGES IN POTATO AS INFLUENCED BYERWINIA CAROTOVORAINFECTION

Abstract

Bacterial soft rot, caused by Erwinia carotovora ssp. carotovora (Ecc), is a major disease in stored potatoes. The pathogen causes different physical, physiological and chemical changes in potatoes, which may affect the acceptability of raw and processed products. This study was carried out to evaluate the effect of disease severity on different physico‐chemical and physiological properties of raw and cooked potatoes and to select the parameters most responsive to disease severity. Potatoes were inoculated with bacteria and incubated at 20C for different lengths of time to produce different levels of disease. As incubation time increased the volume of disease (VDS) increased, which in turn influenced the respiration rate (RR). In both raw and cooked potatoes, the physical changes (texture and color) associated with the progress of disease were reduced hardness, firmness and L value, and increased a and b values and total color difference (ΔE). The chemical changes were reduced ascorbic acid and pH, and increased reducing sugars, total sugars and titrable acidity along with the activities of peroxidase and polyphenol oxidase. The changes in physical and chemical parameters of raw and cooked potatoes during storage were described by fractional conversion equation models. All parameters were quite sensitive to disease except reducing sugars, peroxidase and PPO activity. The correlation matrix indicated that several of the quality parameters were related and thus most of them could be successfully used to predict tuber quality from disease.

Evidence that Cell Death is Associated with Zebra Chip Disease in Potato Tubers

“…While some of these disorders are clearly non-pathologic or 'physiological', many have been positively linked to pathogens, including late blight (Phytophthora infestans) (Levin et al 2001), potato soft rot (Erwinia carotovora pv. atroseptica) (Ghanekar et al 1984;Nourian et al 2002), potato leaf roll virus 'net necrosis' (Murphy 1968), potato virus Y (PVY) (HinrichsBerger et al 1999), potato virus X (PVX) (Mondy and Kock 1978;Cruz and Baulcombe 1993), and common scab (Streptomyces scabies) (Blaszczak et al 2005). The end result of the above-mentioned diseases is the rendering of the tuber unusable as food or as seed for future plantings.…”

Physico‐chemical and sensory attributes in conjunction with multivariate analysis of two potato (Solanum tuberosum L.) cultivars after 90 days of storage: an exploratory authentication study

“…It is known that the maleic acid increased while citric acid decreased with prolonged storage period (Iritani & Weller, 1974). According to Νourian et al. (2002), the total acidity of tubers increased from 0.06% to 0.12% after 133 days of storage at 4 °C.…”

Survey of Tuber pH Variation in Potato (Solanum) Species

“…Perhaps the solids that are excluded from juiced samples contain significant unrecovered acidity in intact vacuoles. Similar methods of mechanical homogenization have been employed by some previous researchers (Arvanitoyannis et al 2008;Hyde and Morrison 1964;Pardo et al 2000;Nourian et al 2002).…”

“…Finotti et al (2006) reported similarly high levels of citric (400 to 600) in Italian cultivars, but Shekar and Iritani (1979) detected much lower levels of citric (150) and malic (30) in stored cv Russet Burbank tubers. Nourian et al (2002) claimed malic acid was the main source of acidity in potato rather than citric, but Shekar and Iritani (1979) failed to find a relationship between malic acid and tuber pH. Roessner et al (2000) also reported high levels of quinic acid.…”

“…Giannuzzi et al (1997) reported that Pseudomonas species in in vitro cultures of homogenated potato flesh are inhibited by very low levels of citric acid, and Dodds (1989) reported that botulism toxin formation is inhibited by lower pH in cooked, vacuum-packed potato products. The pH of tuber tissue infected with soft rot (Erwinia carotovora) has been shown to decrease in response to disease progress (Nourian et al 2002). Ring rot (Clavibacter michiganensis subsp.…”