The quality of New Zealand olive oils: Effect of variety and location on oil quality, as determined by chemical analysis and sensory evaluation, of olives in the South Island of New Zealand: A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticulture Science Honours at Lincoln University

Abstract

The effect of location and variety on olive oil quality was investigated. Olive samples from Barnea, Frantoio, Leccino and Manzanillo varieties were obtained from groves in Waimea, Nelson, Marlborough, Waipara and Canterbury and sent via courier for extraction and subsequent analysis at Lincoln University in Canterbury. Not all localities could provide samples from all the varieties stated and therefore three imported olive oils and two South Island produced commercial olive oils were included in the analysis for comparison. The olive oil samples were analysed objectively using the standard IOOC quality indicators of fatty acid composition, free fatty acids, and peroxide value, as well as analysing for chlorophyll content. The same olive oil samples were evaluated subjectively for the presence of faults, and for preference of panellists using sensory evaluation according to the IOOC standard format. The results from these analyses were analysed statistically for the significance of effect of location and variety on these quality parameters, and for any relationships between the parameters analysed. It was found that the samples of New Zealand olives analysed produced oils which were generally well within the chemical and sensory quality standards for extra virgin olive oil as stipulated by the IOOC. For the olive oils analysed there was a maximum acidity level of 0.20% oleic acid and a maximum peroxide value of 5.05 meq/0₂/kg oil. Both of these are well under the limits specified by the IOOC of no greater than 1 % free fatty acids and 20 meq/0₂/kg for classification as extra virgin. Chlorophyll contents for the 17 oils analysed ranged from a minimum value of 1.7 ppm to a maximum value of 22.8 ppm. Oleic acid was the dominant fatty acid in all of the olive oils analysed with a maximum content of 77.68%. There were very low contents of saturated fatty acids (mean of 12.6%) and polyunsaturated fatty acids (mean of 6.6%) in the profiles of the oils analysed. For most of the olive oils analysed all the values for the main fatty acids lie within the allowable limits for fatty acid contents as enforced by the IOOC. Location and variety consistently had an effect on the chemical quality of the oils analysed. Mean scores awarded for each of the sensory characters were middle of the range or better, relative to the potential score they could be awarded. The majority of oils analysed were perceived to be free from sensory faults, thereby conforming to the IOOC requirement for a median defect value equal to 0. The New Zealand produced oils scored higher in terms of having a more desirable character compared with the imported oil. The sensory characters of the oils analysed were found to be consistently affected by location and variety.