Unraveling Mechanisms of Enzymatic Browning in Nuts and Their Relationship with Pre- and Post-Harvest Factors: Management Strategies for Mitigation.

Gabriela Gavilán-CuiCui, Ricardo Lagos-Muñoz, Felix Miguel Ellena, Antonio Di Matteo, Filis Morina, Cristian Meriño-Gergichevich

Journal: Molecules (Basel, Switzerland) 2025;30(19):

PMID: 41097288

View on PubMed

Abstract

Enzymatic browning (EB) is a physiological alteration that compromises the sensory and commercial quality of tree nuts, significantly reducing their market value and functional compound content. Due to its complexity and economic impact, this review compiles updated information on mechanisms and factors driving EB in tree nut species, as well as strategies for its prevention. The EB in tree nuts results from the oxidation of phenolic compounds (PCs) to brown pigments. This process is driven by enzymatic activity such as polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonium lyase (PAL) and strongly enhanced by cellular stress and associated regulation of gene expression. The EB has been documented in several tree nut species, including almonds, betel nuts, chestnuts, hazelnuts, macadamias, pecans, pistachios, and walnuts. This alteration developed both pre-harvest and post-harvest and was influenced by agronomic factors (such as cultivar, nutritional status, climatic conditions, and altitude) and handling (including shelling, storage, and processing). Mitigation strategies include the use of synthetic inhibitors, physical treatments, and the use of plant extracts rich in natural antioxidants, the latter perceived as more sustainable and safer alternatives.

Address: Doctoral Program in Natural Resources Sciences, Universidad de La Frontera, Temuco 4811230, Chile.; Laboratory of Physiology and Plant Nutrition for Fruit Trees, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Laboratory of Soil Fertility, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Laboratory of Physiology and Plant Nutrition for Fruit Trees, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Laboratory of Soil Fertility, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Department of Agricultural Sciences, University of Naples Federico II, Via Università 100, 80055 Naples, Italy.; Laboratory of Plant Biophysics & Biochemistry, Institute of Plant Molecular Biology, Biology Centre of the Czech Academy of Sciences in Budweis, 370 05 Ceske Budejovice, Czech Republic.; Laboratory of Physiology and Plant Nutrition for Fruit Trees, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Laboratory of Soil Fertility, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.; Scientific and Technological Bioresources Nucleus (BIOREN-UFRO), Universidad de La Frontera, Temuco 4811230, Chile.; Department of Agricultural Production, Faculty of Agricultural Sciences and Environment, Universidad de La Frontera, Temuco 4811230, Chile.

DOI: 10.3390/molecules30193866

MeSH Terms: Nuts, Catechol Oxidase, Phenylalanine Ammonia-Lyase, Antioxidants, Plant Proteins, Phenols, Peroxidase, Oxidation-Reduction