Linking the quality of sweet basil leaves to the quality of pesto : a thesis presented in partial fulfilment of the requirements for the degree of Master in AgriScience (Horticulture) at Massey University, Palmerston North, New Zealand

Abstract

The method for linking basil quality to pesto quality has not been invented but the urgency is certain. If the quality loss of pesto is due to the loss of basil leaves quality, then financial loss suffered by basil-based producer could be reduced by only maintaining basil leaves quality. Through several batches of experiments, the methods of measuring senescence and chilling injury (CI) of basil leaves and the blackening rate of pesto were developed to investigate the impact of pre-processing factors (leaf washing, blanching, and storing) on basil and pesto quality. The final aim was to test whether there was a correlation between senescence or CI in basil leaves and blackening rate of the pesto. The methods included the selection of spectrophotometer proxy, number of replication, processing duration, pesto setting, fitting curve, sampling, cooling techniques, factors that influence all variables, and also solving some issues regarding data and pesto appearance. The result produced several findings. First, measuring senescence or CI of basil leaves could be simply done by cooling basil leaves to a certain level of cold temperature and duration, left them in room temperature for a day and used percentage of rotten leaves and weight loss as the indicators of the symptoms severity. Second, measuring blackening rate of pesto could be done by using L value as the proxy of spectrophotometer and transformed the data into negative exponential to find the K value. Third, there was no correlation between senescence or CI in basil leaves and blackening rate of their pesto. Fourth, pre-processing factors impacted basil quality but not the pesto quality. Washing basil leaves before pesto processing could raising up the initial L value of pesto, blanching could created darker pesto, and storing basil leaves could lead to CI or senescence development, but those factors never affect the blackening rate of pesto. Keywords: Ocimum basilicum, basil, chilling injury, senescence, blackening rate, blanching, temperature, cold storag