Acrylamide in fried sweetpotato: The relationship with free asparagine and effects of asparaginase

Authors: Allan, Matthew; Thomas, Luke Shawn; PECOTA, KENNETH - North Carolina State University; YENCHO, G. CRAIG - North Carolina State University; Johanningsmeier, Suzanne

Submitted to: ACS Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Acrylamide is a potential carcinogen and neurotoxin that can form in foods during cooking by a reaction between sugars and the amino acid asparagine. Sweetpotatoes are relatively high in both sugars and asparagine, making them susceptible to acrylamide formation during frying. Sweetpotato chips were used as a model fried sweetpotato product to investigate the relationship between substrates and acrylamide formation in fried sweetpotatoes and evaluate the efficacy of an enzyme treatment to remove asparagine. ‘Bayou Belle’ sweetpotatoes were grown at two growing locations in 2020 and three locations in 2021, harvested and stored using conventional methods, then processed into chips after 5 to 6 months of storage. Raw sweetpotato slices were also blanched then treated with an enzyme to remove asparagine. Acrylamide levels in chips varied significantly by growing location, and free asparagine content was highly correlated with acrylamide levels while sugars were not. Blanching removed ~50% of the sugars and 83 to 98% of the asparagine; and the enzyme treatment further reduced asparagine to below levels of detection. Acrylamide was reduced 89 to 95% by blanching and 98 to 99% by blanching plus enzyme treatment before frying. In this study, asparagine was clearly demonstrated to be the limiting factor for acrylamide formation in most fried sweetpotatoes, and plausible acrylamide reduction strategies were explored. The findings will help sweetpotato breeders, growers, and processors target reductions in free asparagine as an effective acrylamide mitigation strategy.

Technical Abstract: Sweetpotatoes contain reducing sugars and free asparagine, thus fried products are prone to acrylamide formation. Chips were prepared from ‘Bayou Belle’ sweetpotatoes grown at three locations for 2 years; and sugars, free asparagine, total nitrogen and acrylamide formation were measured. Acrylamide formation was correlated with free asparagine contents of raw sweetpotatoes (r=0.924) with 82-89% being degraded during frying, while total nitrogen was moderately correlated (r=0.505). Sugars were not correlated with acrylamide levels and less than 30% were degraded in frying. Blanching and a post-blanching asparaginase treatment reduced acrylamide levels by 89-95% and 98-99%, respectively. In model solutions, acrylamide formation was associated with free asparagine concentrations (p<0.001), but other free amino acids had an antagonistic effect when total free amino acids exceeded reducing sugars. Free asparagine was the limiting substrate for acrylamide formation in fried sweetpotato, and management of its levels will minimize acrylamide formation in fried sweetpotato products.