et al., 2018 ; Min et al., 2019 ). Most specific operations were similar to those conducted in the previous study. The result is the expression of gallic acid equivalent per kilogram fresh weight. Determination of PAL, PPO, and POD enzyme activities
En-chao Liu, Li-fang Niu, Yang Yi, Li-mei Wang, You-wei Ai, Yun Zhao, Hong-xun Wang, and Ting Min
Xiao-ting Li and Jian-ping Bao
flask, and the volume was determined using glacial acetic acid. The solution to be tested was placed in a colorimetric dish, and absorbance was measured at 280 nm to obtain the optical density value. Determination of POD, PPO, and PAL activities
Ting Min, En-chao Liu, Jun Xie, Yang Yi, Li-mei Wang, You-wei Ai, and Hong-xun Wang
greatly enhance the shelf life and overall quality of fresh produce ( Mcdonald and Sun, 2000 ). Phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) are involved in the enzymatic browning of many fruits and vegetables
Ting Min, Li-Fang Niu, Jun Xie, Yang Yi, Li-mei Wang, You-wei Ai, and Hong-xun Wang
has been most successful in maintaining quality and prolonging the shelf life of fresh-cut lotus root ( Aquino-Bolanos et al., 2000 ; Sharma and Rao, 2017 ; Toivonen and Brummell, 2008 ). Total phenolic content, oxygen, PPO, and POD are known to be
Pavlos Tsouvaltzis, Angelos Deltsidis, and Jeffrey K. Brecht
., 2004 ). This disruption liberates PPO enzyme from mitochondria, allowing it to contact phenolic substrates in the vacuole and oxidize them to quinones, which then polymerize to dark pigments ( Friedman, 1997 ; Martinez and Whitaker, 1995 ). ‘Russet
Dangyang Ke and Mikal E. Saltveit Jr.
A 1.5% O2 atmosphere, relative to normal air, dramatically inhibited ethylene-induced russet spot development, PAL, and ionically bound POD, and ionicaliy bound IAA oxidase activities and reduced soluble phenolic content in stored iceberg lettuce (Lactuca sativa L.). Low O2 also inhibited eythylene production and respiration. Polyphenol oxidase activity was slightly inhibited by low O2. The results suggest that low O2 inhibition of ethylene action and attendant effects on phenolic metabolism and IAA oxidase activity may be responsible for inhibition of russet spotting by 1.5% O2. Chemical names used: indole-3-acetic acid (IAA); phenylalanine ammonia-lyase (PAL); peroxidase (POD); polyphenol oxidase (PPO).
Joshua D. Klein
Susceptibility of apples (Malus domestica Borkh. ‘Gala’ and ‘Granny Smith’) to impact damage increased from early to late harvest time and decreased during storage at 1°C. Impact damage was quantified as bruise depth, diameter, volume, or weight. Bruise weight calculated as a percentage of fruit weight was the least variable measurement of bruising that was also proportional to height to impact of the fruit. Although a range of 22 New Zealand-grown apple cultivars differed in susceptibility to bruising, the variation was not correlated with fruit density, fruit firmness, or polyphenol content and polyphenoloxidase (PPO) activity in epidermal and cortical fruit tissues.
Dangyang Ke and Mikal E. Saltveit Jr.
Leaf midrib tissue from six cultivars of iceberg lettuce (Lactuca sativa L.) was excised from 20- to 100-day-old plants and tested at 5C for russet spotting (RS) susceptibility under 10 μl ethylene/liter. There was no RS development in tissue excised from 20-day-old plants from any of the six cultivars. RS first developed in tissue from 50-day-old plants and tended to be more severe in tissue excised from older plants. ‘Winter Haven’ and ‘Salinas’ were most susceptible, while ‘Calmar’ was most resistant to RS; ‘Climax’, ‘El Toro’, and ‘Sea Green’ were moderately susceptible. Phenylalanine ammonia-lyase activity in the six cultivars at different developmental stages correlated with their degree of RS development. For ‘Winter Haven’, the increase in ionically bound POD and IAA oxidase activity, but not PPO activity, was associated with the increase in RS score during plant development. ‘Winter Haven’ tissue had much higher ionically bound peroxidase and IAA oxidase activities than ‘Calmar’ tissue from 100-day-old plants. Chemical names used: indole-3-acetic acid (IAA), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO).
Andrés Olivos, Scott Johnson, Qin Xiaoqiong, and Carlos H. Crisosto
consequence of oxidative degradation of phenolic compounds by polyphenol oxidase (PPO), which leads to production of quinones that polymerize rapidly to form brown-colored products ( Kader and Chordas, 1984 ). The concentration of phenolic compounds, the
Ting Min, Jun Xie, Yang Yi, Wenfu Hou, Youwei Ai, and Hongxun Wang
), polyphenol oxidase (PPO), and peroxidase (POD) have been reported previously as being involved in enzymatic browning of many species ( Banerjee et al., 2015 ; Cheng et al., 2015b ; Zheng et al., 2016 ; Zhou et al., 2003 ). Our previous research reported