Crude polyphenol oxidase (PPO) was extracted from pawpaw (Asimina triloba) fruit pulp, partially purified by gel filtration and electrophoresed for molecular weight (MW) determination. The enzyme activity was assayed by monitoring the absorbance (420 nm) of the PPO extract‐catechol mixtures over time. The PPO activity varied with pH and was the greatest at pH 6.5–7.0. The crude enzyme exhibited a maximum activity at 5–20C, but a brief exposure to 40–80C resulted in a rapid decline or complete loss of the enzyme activity. The enzyme kinetics based on the reaction rate in the linear region (0–60 s) showed a Vmax of 0.1363/s and a Km of 0.3266 M for the crude PPO. The PPO existed as two isoforms with MWs of 28.2 and 38.3 kDa, respectively. PRACTICAL APPLICATIONS Pawpaw fruit is a low‐acid, sweet and aromatic fruit grown in North America. With its intense flavor resembling a combination of banana, mango and pineapple, pawpaw fruit is being used in value‐added products such as ice creams, yogurts and baked foods. However, pawpaw fruit has a short postharvest shelf life because it is susceptible to brown or even black discoloration when stored at ambient temperatures. This study has identified that polyphenol oxidase, an enzyme that oxidizes phenols (an endogenous compound present in pawpaw fruit pulp), is the cause for the discoloration. We also found that this enzyme is most active at neutral pH and at room temperature. These findings are important because they could help pawpaw growers and food processors to develop proper storage and processing methods to avoid the undesirable color changes.
Shell-on tails of male (M), nonspawning female (F), and spawning female (SF) Australian red claw crayfish (Cherax quadricarinatus) (n = 270) were aerobically stored at 2• C up to 10 d to monitor meat quality changes under a retail condition. Percentage protein of SF muscle was higher (P < 0.05) and moisture and ash content lower (P < 0.05) than those of M and F muscles. The pH of muscle changed during storage, with SF generally having a lower value than M or F (P < 0.05). Lipid oxidation increased during the 1st 5 d and no significant difference existed between the 3 muscle groups. Cooking yield of SF (91.72%) at 10 d was significantly lower than that of M (96.25%) or F (97.81%), and its muscle shear force was also higher (P < 0.05) than M at 0, 3, 5, and 7 d and than F at 5 and 7 d. Sensory panel results (cooked meat tenderness, juiciness) were significantly correlated with instrumental results (shear force, cooking yield), with SF showing a lower meat tenderness, juiciness, and overall acceptability than M and F samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.