Inhibition of enzymatic browning in sweet potato (Ipomoea batatas(L.)) with chemical and natural anti‐browning agents

Abstract

Honey, pineapple, chilli pepper, and onion extracts were investigated for their ability to inhibit enzymatic browning in sweet potatoes. Honey had the highest inhibition (41.39%–48.0%), comparable with l‐ascorbic acid. Heated onion extract increased polyphenol oxidase (PPO) inhibition by 2.5‐fold when 4‐methylcatechol was used as substrate. However, percentage inhibition decreased drastically (7.42%–19.67%) when heated pineapple extract was used. Fresh chilli pepper extract showed a higher PPO inhibition (45.97%) than that of heated extract. These natural inhibitors were also compared to synthetic inhibitors that ranked: l‐cysteine > l‐ascorbic acid > sodium chloride. l‐cysteine was the most effective chemical inhibitor which inhibited up to 70.4% PPO activity. It was found that natural inhibitors extracted from common food items are able to control the enzymatic browning of sweet potato. These natural inhibitors extracts are safe to human and would also be potentially replaced chemical inhibitors for the preservation of other fruits as well as vegetables. Practical applicationsFruits and vegetables are prone to enzymatic browning. This is caused by the oxidation reaction of endogenous phenolic compounds, catalyzed by PPO. PPO oxidizes o‐diphenols to o‐quinones, which will turn into brown pigments as the o‐quinones polymerize immediately. Enzymatic browning of fruits and vegetables always take places after harvest, during the post‐harvest processing as well as storage. Thus, identification of suitable and acceptable inhibitors is important in order to prevent food browning and to increase the food marketability for food industry. This study indicated that sweet potato PPO was successfully inhibited by extracts from common food items such as honey, chilli pepper, pineapple, and onion which are safe for human consumption. Thus, these natural inhibitors could also be applied to similar food materials such as apples, star‐fruit, and normal potatoes. We expect that the inhibitors examined in this study can be isolated and identified as lead molecules for the development of natural anti‐browning food additives.

Purification and biochemical characterization of polyphenol oxidase extracted from Kirmizi Kismis grape (Vitis viniferaL.)

“…IC 50 value for ascorbic acid in similar studies was found, 069 mM for tea leaf PPO (Öztürk et al, 2020), 0.80 mM in sweet potato PPO (Lim et al, 2019) (Han et al, 2019).…”

Heated plant extracts as natural inhibitors of enzymatic browning: A case of the Maillard reaction

“…Moreover, the Maillard pathway/route linked with the pH value in the range of pineapple juice (3.52-5.2) is associated with the formation of HMF via 1,2 enolization of ARPs at pH ≤ 7. We are, therefore, linking the results reported above by Rattanathanalerk et al (2005) concerning HMF formation and those by Lim et al (2019). However, properties.…”

“…The superiority of heated over unheated/fresh plant extracts in inhibiting EB was attributed to the development of the MR during heating, thus production of MRPs (Barbagallo et al, 2012;Kim et al, 2005;Lim et al, 2019;Redondo et al, 2016;Wong & Angel Lee, 2014). Although authors concluded thus, only the study conducted by Redondo et al (2016) Abbreviations: L-DOPA, L-dihydroxy phenylalanine; PPO, polyphenoloxidase; REA, residual enzyme activity which is also termed relative enzyme activity.…”

“…TA B L E 2 (Continued) Lim et al, 2019;Lim & Wong, 2018;Roldán et al, 2008;Wong & Angel Lee, 2014) (Table 2). The inhibitory effect of fresh onion was attributed to it being a rich source of bioactive compounds.…”

Sequencing, assembly, annotation, and gene expression: novel insights into browning-resistant Luffa cylindrica

“…(Okada, Katsura & Kobayashi, 2004;Purlis & Salvadori, 2007;Troup et al, 2015;Lee & Knag, 2017). However, browning can affect the flavor and reduce the nutritional value of most fruits and vegetables and is therefore considered the second largest cause of quality loss (Lim, Cheun & Wong, 2019). The two main types of browning are as follows: enzymatic browning, which is the result of polyphenol oxidase (PPO) that catalyzes the formation of quinone and its polymer; and non-enzymatic browning, which involves Maillard reaction and caramelization (Buera et al, 1987;Zamora & Hidalgo, 2005).…”