Understanding chemical pathways of brown centre formation in laboratory induced and conventionally dried nut-in-shell macadamia kernels.

Autor:	Martinez M; Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD, 4111, Australia., Wallace HM; Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD, 4111, Australia., Searle C; MacAvo Consulting, Pashley's Road, Welcome Creek, QLD, 4670, Australia., Elliott B; Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD, 4111, Australia., Hosseini Bai S; Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD, 4111, Australia.
Jazyk:	angličtina
Zdroj:	Heliyon [Heliyon] 2024 Jan 30; Vol. 10 (3), pp. e25221. Date of Electronic Publication: 2024 Jan 30 (Print Publication: 2024).
DOI:	10.1016/j.heliyon.2024.e25221
Abstrakt:	World tree nut production has increased rapidly by around 50 % in the past decade; however, nut defects cause losses. For example, we know that brown centres are a major internal discolouration defect in macadamia nuts and are linked to the storage of nut-in-shell under improper conditions at high temperature and humidity. However, key chemical changes in brown centre kernels have not been described. In this study, we compared brown centres and white kernels from: 1) samples that were "induced" in the laboratory by storing at high moisture concentration; and 2) samples that were dried immediately after harvest using industry best practice methods recommended by the Australian Macadamia Society (AMS). We measured the moisture concentration, sugar concentration, fatty acid concentration, peroxide value, nutrient concentration and volatile compounds of induced and AMS samples. Our results showed that storing nut-in-shell macadamia under wet and hot conditions increased brown centres compared with samples immediately dried using the AMS regime, 10.33 % vs 1.44 %, respectively. Induced brown centres had significantly higher moisture concentrations than induced white centres. Volatile compounds including nonanoic acid, octanoic acid and 2,3 butanediol were identified and associated with brown centre formation in macadamia kernels and the initiation of lipid oxidation. Our results suggest sugar hydrolysis and the Maillard reaction are associated with brown centres both in laboratory induced samples and those formed using industry best practice drying methods. Our study suggests improper drying and storage at high temperature and high humidity are likely to result in brown centre formation. We recommend brown centre losses can be reduced by appropriate drying and storage practices. Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Shahla Hosseini Bai - Helen Wallace reports financial support was provided by Macadamia processors including Hinkler Park Plantations, Macadamias Australia, RFM Macadamias and TQ Holdings Pty Ltd. The authors would like to declare that co-author Chris Searle works as a consultant for the Macadamia industry, through the business MacAvo Consulting, however this consulting relationship had no influence on the research undertaken in this manuscript. The financial supporters had no influence to interpret data involved in this research, or in the writing of this manuscript. (© 2024 The Authors.)
Databáze:	MEDLINE
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