Heat stability of trypsin inhibitors in tropical root crops and rice and its significance for nutrition

Abstract

Abstract:The heat stability of trypsin inhibitors from rice (Oryza sativa L), sweet potato (Ipomoea batatas (L) Lam), taro (Colocasia esculenta var esculenta ( L ) Schott), giant taro (Alocasia macrorrhiza (L) G Don) and giant swamp taro (Cyrtosperma chamissonis (Schott) Merr) was studied. Rice trypsin inhibitor (TI) occurred only in the germ, so it is absent from white rice. Taro, giant taro and giant swamp taro (but not rice or sweet potato) showed an initial large increase (one-to tenfold) in the amount of TI present on heating at about 80°C. The heat release mechanism, which was accompanied by a change to a rubbery texture in the food, amounted to a breakdown of the cellular structure making TI available for extraction. Such heat release of TI would cause partially cooked food to be deleterious for human consumption. Brown rice, sweet potato, taro and giant swamp taro contained moderate amounts of TI, which was fully inactivated when the boiled or baked food was soft enough to eat. Giant taro, however, contained 10-100 times as much TI (which in this case also inhibited chymotrypsin) as the other foods, and a boiling time of at least 30 min was needed for its inactivation.

Effect of Processing on Amylase and Protease Inhibitor Activity in Tropical Tubers

“…During boiling, it was generally observed that enzyme inhibitory activity decreased with increase in boiling time. Increase in activity of trypsin inhibitor was not observed during the initial phase of cooking as reported by Bradbury et al (1992) probably due to differences in methodology used to extract the inhibitor. The retention of trypsin inhibitor was significantly decreased when the size of the tuber piece was reduced, possibly due to its leaching out into the cooking medium.…”

“…Although amylase and protease inhibitors occur in many food plants, very little is known about their antinutritional properties. Many of the inhibitors found in seeds, bulbs, and tubers have been reported to be partially or completely inactivated by heat indicating that their inhibitory activity is probably reduced when these foods are subjected to various heat treatments (Bradbury et al 1992;Mulimani and Supriya 1993;Nagaraj andPattabiraman 1985 andPrathibha et al 1995). Studies on the effect of heat on inhibitor activity have mainly been confined to in vitro experiments using crude or semi purified preparations of various enzyme inhibitors.…”

“…Since all these tubers are processed before they are consumed, it is important to know whether inhibitory activity is present in tubers after they are processed. Reports indicate that some of the enzyme inhibitors present in food plants are heat labile indicating that they may be inactivated during processing Pattabiraman 1975, 1979;Shivaraj and Pattabiraman 1980;Sharma and Pattabiraman 1980;Prathibha et al 1995;Mulimani and Supriya 1993;Bradbury et al 1992;Nagaraj and Pattabiraman 1985). A variety of methods are generally used for processing these tubers.…”

Nutrient and Antinutrient Composition of Cormels ofColocasia esculentavar.antiquorum

“…'Sonajuli' appears to be the best cultivar despite possessing the highest score for trypsin inhibitor, which becomes inactivated by prolonged boiling during preparation of food from taro (Bradbury et al, 1992). Based on the results, it is indicated that 'Sonajuli' represents promising genetic material from which improved lines may be developed.…”

Effect of heat treatment on forage quality of bio-fortified orange fleshed Ipomea batatas crop residues and roots

“…Traditional preservation methods such as air-drying, baking and powdering, cooking, steaming and fermentation change plant physiochemical properties, deactivate inhibitors (Yadang et al, 2013;Ahmed et al, 2010;Kirana and Padmaja, 2003) and inactivate spoilage enzymes. Senanayake et al (2013), Zhang and Corke (2001), and Lin (1989) confirmed that heating was effective against trypsin inhibitors; while Bradhury et al (1992), Colonna et al (1992) and Walter et al (1976) noted that heat increased hydrolysed starch to maltose increasing its digestibility. Processing, however, destroy carotenes, lowers amino acid, mostly lysine bioavailability and reducing sugars (Walter and Purcell, 1986) and affects antioxidant activity.…”