title: Characterisation of the aroma profiles of New Zealand monofloral honeys

authors: Thomas, Edie Rose

subjects: Honey

abstract: New Zealand hosts a variety of monofloral honeys with distinct aromas and flavours. These sensory properties are determined by the volatile organic compounds present in the honey, of which over 600 have been identified. The volatile profile of honey is primarily influenced by botanical origin, geographic origin, storage and processing conditions. Not all compounds in the volatile fraction are represented in the aroma profile of the honey, due to the varying odour thresholds at which compounds can be detected by the consumer. Volatile compounds in New Zealand honeys have previously been studied for authentication purposes, but no New Zealand studies to date have linked the volatile composition with honey aroma. Thus, the aim of this research was to develop and optimise a method for the extraction and analysis of volatile compounds in New Zealand monofloral honeys, to determine the chemical differences responsible for the unique aromas of honeys of different botanical origins.
Various methods were trialled for the extraction of the volatiles, which are present in very low concentrations, from the complex honey matrix. Solvent extraction using dichloromethane was chosen, and samples were analysed by gas chromatography-mass spectrometry in selected ion monitoring mode. This demonstrated excellent sensitivity at the low part-per-billion level and allowed for identification of compounds not seen in total ion chromatograms. The method showed excellent precision and linearity over wide concentration ranges. Eighteen compounds were semi-quantified using this method, with full quantification achieved for four of these: nonanal, cineole, benzyl alcohol and guaiacol. Additional volatiles were screened using total ion chromatogram.
The optimised method was used for the analysis of 44 New Zealand monofloral honey samples spanning 11 floral origins. All 18 compounds were detected in all honey types, but not in all samples. ᴅ limonene, β-ionone and cineole are reported for the first time in any New Zealand honey, and phenylacetaldehyde and nonanal are reported for the first time in kānuka (Kunzea ericoides) honey. Results were comparable with the literature for these honey types, with mānuka honey characterised by o-methoxyacetophenone and kāmahi honey by 4-oxoisophorone. New Zealand clover honey contained low levels of volatiles which has also been reported for international clover honeys. The volatile profiles were also compared with odour thresholds to suggest possible aroma contributors for each honey type. Nonanal was determined to be aroma-active in all honeys analysed, and cineole in all but ling, lotus/blackberry and rātā. Chemometric methods including principal component analysis, classification and regression trees and linear discriminant analysis were used to identify similarities in samples based on their volatile profiles. Samples were classified by honey type using linear discriminant analysis with 82.9% accuracy, with the most accurate classification achieved for kāmahi and kānuka honeys.

text: Characterisation of the aroma profiles of New Zealand monofloral honeys New Zealand hosts a variety of monofloral honeys with distinct aromas and flavours. These sensory properties are determined by the volatile organic compounds present in the honey, of which over 600 have been identified. The volatile profile of honey is primarily influenced by botanical origin, geographic origin, storage and processing conditions. Not all compounds in the volatile fraction are represented in the aroma profile of the honey, due to the varying odour thresholds at which compounds can be detected by the consumer. Volatile compounds in New Zealand honeys have previously been studied for authentication purposes, but no New Zealand studies to date have linked the volatile composition with honey aroma. Thus, the aim of this research was to develop and optimise a method for the extraction and analysis of volatile compounds in New Zealand monofloral honeys, to determine the chemical differences responsible for the unique aromas of honeys of different botanical origins.
Various methods were trialled for the extraction of the volatiles, which are present in very low concentrations, from the complex honey matrix. Solvent extraction using dichloromethane was chosen, and samples were analysed by gas chromatography-mass spectrometry in selected ion monitoring mode. This demonstrated excellent sensitivity at the low part-per-billion level and allowed for identification of compounds not seen in total ion chromatograms. The method showed excellent precision and linearity over wide concentration ranges. Eighteen compounds were semi-quantified using this method, with full quantification achieved for four of these: nonanal, cineole, benzyl alcohol and guaiacol. Additional volatiles were screened using total ion chromatogram.
The optimised method was used for the analysis of 44 New Zealand monofloral honey samples spanning 11 floral origins. All 18 compounds were detected in all honey types, but not in all samples. ᴅ limonene, β-ionone and cineole are reported for the first time in any New Zealand honey, and phenylacetaldehyde and nonanal are reported for the first time in kānuka (Kunzea ericoides) honey. Results were comparable with the literature for these honey types, with mānuka honey characterised by o-methoxyacetophenone and kāmahi honey by 4-oxoisophorone. New Zealand clover honey contained low levels of volatiles which has also been reported for international clover honeys. The volatile profiles were also compared with odour thresholds to suggest possible aroma contributors for each honey type. Nonanal was determined to be aroma-active in all honeys analysed, and cineole in all but ling, lotus/blackberry and rātā. Chemometric methods including principal component analysis, classification and regression trees and linear discriminant analysis were used to identify similarities in samples based on their volatile profiles. Samples were classified by honey type using linear discriminant analysis with 82.9% accuracy, with the most accurate classification achieved for kāmahi and kānuka honeys.

year: 2023

title: Two phase aqueous extraction of whey proteins in a polyethylene glycol - arabinogalactan system

authors: Ng, Timothy Wei Choong

subjects: two-phase aqueous extraction

abstract: The whey protein separation potential of aqueous two-phase systems of arabinogalactan [AG] (Lonza FiberAidTM) and polyethylene glycol [PEG], buffered with 10 mmol/g phosphate or citrate buffer, was studied. 100 mmol/g potassium chloride [KCl] was added as required. Previously-published phase equilibrium results were verified and the absorbance of whey protein isolate [WPI] in an AG-PEG solution was measured. The effect of pH, KCl concentration, initial WPI concentrations and upper to lower phase mass ratios on whey partitioning was studied. The best separation system contained 17.20% (w/w) AG, 7.20% (w/w) PEG, 10 mmol citrate buffer (pH 5.4) and 100 mmol KCl per gram of total system. The upper to lower phase mass and volume ratios were 1:1 and 16:11 respectively. Approximately 12 mg (mainly α-lactalbumin) of the 20 mg WPI added partitioned into the AG-rich upper phase. This system has potential to reduce chromatographic requirements in large scale separation of protein mixtures.

text: Two phase aqueous extraction of whey proteins in a polyethylene glycol - arabinogalactan system The whey protein separation potential of aqueous two-phase systems of arabinogalactan [AG] (Lonza FiberAidTM) and polyethylene glycol [PEG], buffered with 10 mmol/g phosphate or citrate buffer, was studied. 100 mmol/g potassium chloride [KCl] was added as required. Previously-published phase equilibrium results were verified and the absorbance of whey protein isolate [WPI] in an AG-PEG solution was measured. The effect of pH, KCl concentration, initial WPI concentrations and upper to lower phase mass ratios on whey partitioning was studied. The best separation system contained 17.20% (w/w) AG, 7.20% (w/w) PEG, 10 mmol citrate buffer (pH 5.4) and 100 mmol KCl per gram of total system. The upper to lower phase mass and volume ratios were 1:1 and 16:11 respectively. Approximately 12 mg (mainly α-lactalbumin) of the 20 mg WPI added partitioned into the AG-rich upper phase. This system has potential to reduce chromatographic requirements in large scale separation of protein mixtures.

year: 2014

title: Huikau

authors: Maxwell, Te Kahautu

abstract: Huikau is dedicated to my life long mentor and educator Mrs Ema Rogers who imparted her knowledge of Te Haahi Ringatū and things Māori to me. She housed me for months while I reseearched my MA Thesis Te Kōpura. Mrs Rogers passed away in December 2012. This new composition was performed by Ōpōtiki Mai Tawhiti Kapa Haka at the Mātaatua Regional Kapa Haka Competition. This composition placed first in the Waiata Tira category.

text: Huikau Huikau is dedicated to my life long mentor and educator Mrs Ema Rogers who imparted her knowledge of Te Haahi Ringatū and things Māori to me. She housed me for months while I reseearched my MA Thesis Te Kōpura. Mrs Rogers passed away in December 2012. This new composition was performed by Ōpōtiki Mai Tawhiti Kapa Haka at the Mātaatua Regional Kapa Haka Competition. This composition placed first in the Waiata Tira category.

year: 2012