Factors influencing acridity level NARI taro (Colocasia esculenta) in Papua New Guinea

A projecgt undertaken at the Papua New Guinea National Agricultural Research Institute, and supervised by Joel Pilon

Edible aroids Colocasia esculenta, commonly known as taro, are amongst the potential root and tuber crops in Papua New Guinea (PNG). The crop is high in starch content, is low in protein and lipid, and is a potential source of renewable energy and industrial raw material. However, its potential remains to be realized in the development of agro food industries especially in PNG. Despite its wide application and great potential as a chief dietary source of carbohydrate and other essential nutrients, its usage is often limited by the presence of anti-nutrients, which are either potentially toxic, may limit the bioavailability of other nutrients, or make the food item less palatable to consumers.

Taro acridity is caused by needle-like raphides; crystals of calcium oxalate which constitute up to 2.05 to 4.21% DM. Presumably, itchiness arises when the calcium oxalate crystals are released and inflict minute punctures on the skin when in contact with it. Crystals have to interact with a certain chemical on the raphides’ surfaces before acridity is experienced (Bradbury and Nixon 1998; Paull et al. 1999; Kaushal et al. 2015). Several techniques have been developed and successfully applied to minimize the level of acridity. These includes washing, which can reduce oxalate content by 9.2% (Huang et al, 1998), boiling by 23.5% (Huang et al. 2010), soaking by 56.7% (Shanthakumari et al., 2011), peeling, dicing, drying or baking and other application of thermal treatments. Although these treatment processes (drying, boiling, baking, soaking, peeling and dicing) can reduce acridity level, they can also cause negative attributes to the final food product, as evidenced in the decreased photochemical contents of taro noodles and cookies and lowering of the nutritional value (Alcantara, et al. 2013; Akpan and Umoh 2004; Tagadoe and Nip 1994).

This research looks into the contributing factors influencing acridity in taro, such as fertilizer application and soil water holding capacity. This will create a basis for understanding trends of acridity and ways to realise taro as a value-added crop within fresh food markets in PNG and elsewhere.

 

Figure 1. NARI breeding line (NARI TARO 2) that has moderate acridity level, tested on non water logged land.

Figure 2. Numkowe a Local TARO Cultivar with less moderate acridity level, tested on non water logged land.