Effects of clonal variations on the chemical and Organoleptic qualities of green tea processed on Mambilla highland, Nigeria

¹Aroyeun S.O., ²Odumbaku, ²L.O., ²Oloyede, A.O., ²Adebiyi, D.A. and ²Majolagbe, I.R.

¹Cocoa Research Institute of Nigeria, PMB, 5244, Ibadan, Oyo State

²Moshood Abiola Polytechnic, Abeokuta, Ogun State

Corresponding author Email: aroyeun2000@yahoo.co.uk,

Accepted 26 March, 2012

Abstract

Green tea was processed from seven different tea clones 68, 65, 35, 228, 236, 318 and 143 in this study using Chinese method of green tea processing which include, Plucking, Fixing, Rolling and Drying. Mineral elements, Polyphenols, Tannin, Caffeine, Vitamin C and β-carotene of the processed green tea were evaluated. The Sensory evaluations of the Green tea infusions was carried out to determine the effect of tea clonal variations on the sensory attributes of taste, colour, aroma, and overall acceptability. The results obtained in this study indicated   significant variations (p<0.05)  in mineral elements based on clonal differences. Heavy metal elements were in the range of 0.011-0.32ppm for Cd, 0.001-0.005 for  Ni and 0.09-0.27ppm, for respectively. The safety of  all these samples were assured as their contents were significantly lower than the values within the safety threshold as speculated by WHO. Some trace metals like Iron, Fe; Nickel, Ni, and Zinc Zn, which are essential, for growth also varied significantly (p<0.05) and ranged between 30-250ppm for Iron,   0.001-0.005, for Ni, and 33.67-52.6ppm for Zinc respectively. Some agronomic factors might have played a significant role in the mineral constituents’ as evidenced in this study. The choice of clones for mineral components will depend on high contents of essential elements such as Magnesium, Iron, Zinc, low contents of toxic/heavy metals like Cadmium, Lead, and Nickel. Low caffeine, low tannin, high polyphenol, high  vitamin C, High β-carotene and organoleptic values. Based on all these parameters, our findings established that clone 68 has a high levels of essential elements: Zn (52.6ppm), ; Fe (180ppm), K (70.37ppm), and Sodium (44.47ppm). The Caffeine content ranged between 1.29-2.56% w/w with a mean of 192% and differed significantly from clone to clone. The total polyphenols TPC ranged between 22.1% -53.4%. Vitamin C of the green tea also varied significantly with clonal variations. Clone 35 had the highest vitamin C content of 0.46% followed by clone 236 (0.365%), cone 61 (0.17%), clone 68 having 0.11% of vita min C. The percentage Tannin of the green tea was relatively low. β-carotene also varied according to the clones and is in the order 35>318>61>363>68>228. Sensory evaluation showed significant differences among the green tea infusions in taste, aroma, colour and overall acceptability.

Keywords: Green tea, clones, elements, heavy metals, organoleptic