Cyanogenic compounds removal and characteristics of non- and pregelatinized traditional detoxified wild yam (Dioscorea hispida) tuber flour

Abstract

The presence of cyanide compounds restricts the utilization of wild yam (Dioscorea hispida) tubers for food or food ingredients. Traditional detoxification, usually used in wild yam chips processing, has not been evaluated for its effectiveness in reducing cyanogenic compounds. Processing into flour will increase wild yam tubers utilization and pregelatinization usually improve flour functional properties. This study aimed to evaluate the effect of 4 traditional detoxification methods and pregelatinization on cyanogenic compounds removal and wild yam tuber flour characteristics. The different methods were in rubbing ash, soaking time, and pregelatinization methods by boiling or steaming. The duration of a particular step was also different. The results showed that traditional detoxification methods reduced total cyanides 97%, cyanogenic glycosides 98-100%, acetone cyanohydrin 89-97%, and HCN 94-95%; also affected degree of cyanogenic compounds removal. Pregelatinization also reinforced the degree of cyanogen removal. Tuber flour physicochemical properties were affected by detoxification methods and pregelatinization. Modification of starch might occur due to the presence of SiO 2 and calcium in rubbing ash and affected functional properties of wild yam tuber flour. Starch granule morphology appeared not to be affected by detoxification methods. Traditional detoxification methods could be used to make a safe wild yam tuber flour.

Traditional detoxification of wild yam (Dioscorea hispida Dennst) tuber in chips processing at East Java, Indonesia

“…Four traditional detoxification methods from four locations (Kandangan Sub-district, Kediri Regency; Paiton Sub-district, Probolinggo Regency; Wates Sub-district, Kediri Regency; Ngaglik Sub-district, Blitar Regency) were conducted at the laboratory for analysis of the pH at every step in wild yam tuber chips processing. The cyanogenic changes during wild yam chips processing were from our previous study [ 22 ]. The discussion to elucidate the scientific evidence behind every step of wild yam tuber detoxification based on the relevant literature.…”

“…HCN content of wild yam tuber was 84.26 ppm [ 31 ], and total cyanide content of 379–739 ppm [ 32 ]. The previous study [ 22 ] showed that wild yam tuber contained HCN of 54.74 ± 0.17 ppm, acetone cyanohydrin of 3.91 ± 0.28 ppm, a cyanogenic glycoside of 24.55 ± 0.21 ppm, and total cyanides of 83.20 ± 0.11 ppm. FAO/WHO determined that the safe limit of cyanide ingestion is 10 ppm [ 33 ].…”

“…The type of ash also varies between chip makers, most of them use wooden ash, but there is also the use of the mixture of wood ash and rice straw (Table 1 ). CaO dominates the mineral composition of the rubbing agent of ash and salt, and rice straw contributes to the concentration of SiO 2 [ 22 ]. The minerals from the ash increase the pH of the sliced tubers (Table 2 ).…”

“…The toxicity of cyanogenic glycoside is estimated based on the quantity of generated free cyanide from hydrolysis [42]. The main problem of wild yam tuber is that cyanogenic glycoside is the predominant cyanogenic compound [22].…”

“…In the 1980s, wild yam could be found in Indonesian markets, especially on Java Island, as wild yam tuber chips [ 1 ]. The chips are prepared traditionally to remove the toxic cyanogenic compounds by several steps, and there is a variability of preparation among places [ 22 ]. This paper aims to review the cyanogenic removal in every step of traditional wild yam tuber chips processing.…”