Oat groat colour : A quality factor : A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours in Lincoln University

Abstract

Colour has been identified as an important component of consumer judgement of oat based products. Preference has been for lighter golden brown Australian oats compared with the darker New Zealand oats. In this study, industry experts were used to assess preference of 30 cereal samples of different colours selected from 125 screened samples. Colour was quantified by the CIE L*a*p* colour space, hue and chroma.

Regression analysis indicated preference was related to the a* (r² = 0.64) and hue (r² = 0.59) components of colour, and not the L * (r² = 0.01 ), b* (r² = 0.03), or chroma (r² = 0.00) components. Preferred samples had low a* (5.12) and high hue (78.43) values indicating preference was related to movement from the red to the yellow region of the colour space. The effect of nitrogen (100 and 200 kg N/ha), Cycocel growth regulator (0 and 1.75 I ai/ha), and sowing rate (100 and 200 kg/ha) on the colour components was examined. Only Cycocel caused a change (p<0.05) in the a* (23.23 to 23.30) and hue (77.10 to 76.68) values. Agronomic options to alter oat groat colour appeared limited. Fungal contamination by Alternaria and Fusarium species was identified as the cause of oat groat discolouration, between 1995 and 1996 samples of cv. Drummond, rendering this recommended cultivar unacceptable to oat millers. Chemical analyses of oats indicated 11 of 16 samples had tyrosinase activity above those in wheat (8.89 x 10⁻⁵ U/mg of grain) but this was not associated with colour preference. Screening of breeders lines for a* values less than 6.5 may lead to increased acceptance of New Zealand oat cultivars provided a* is genetically controlled.