Macadamia nuts have high nutritional value and positive health attributes. Changes to the composition and availability of these compounds during roasting contribute to product quality. In this study, changes to the chemical composition of lipids (fatty acids, triglycerides, and free fatty acids) and other phytochemicals were analyzed, and a sensory evaluation was carried out of two major varieties of macadamia nuts planted in China, after roasting. Only small changes in fatty acid (FA) content and a slight decrease in total triglycerides (TAGs) were observed after roasting. The free fatty acid (FFA) content and the peroxide value were increased by roasting. The total available polyphenol content increased by 25.6% and the oxidative stability index of kernels increased by 21.6%. The sensory scores for taste and aroma were doubled by roasting. Overall, the sensory, nutritional quality, and oxidative stability of roasted macadamia nuts were greatly improved, compared with raw nuts.

This paper analyzed the effects of four drying methods (heat pump drying, hot air drying, sun drying, and freeze drying) on the volatile organic compounds (VOCs) in fresh ‘Guiyan1’ Amomum villosum Lour.

This study aims to understand the main nutrient composition and comprehensively evaluate the differences in the mineral element contents of fruits of different macadamia cultivars, as well as screen good cultivars that are suitable for use in rocky desert mountains. Nine macadamia nut cultivars were selected as test materials in rocky desert mountain orchards. The contents of crude fat, crude protein, and total soluble sugar in kernels and N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B in peels and kernels were determined, respectively. Then, the kernels’ mineral element contents were comprehensively evaluated based on principal component analysis. The results showed that the kernels were rich in crude fat, protein, and soluble sugar, with the crude fat content reaching 75% or greater, and the variation among cultivars was small. However, the variation in soluble sugar content was extensive. The content of mineral elements varied in different cultivars and parts of the fruit, with the average macronutrient content being K > N > Ca > P > Mg in the pericarp and N > K > P > Mg > Ca in the kernel, and the content of micronutrients in the pericarp and the kernel being Mn > Fe > Zn > Cu > B. By principal component analysis, the 10 mineral nutrient indexes were calculated as four principal components, with a cumulative contribution rate of 88.051%. Using the affiliation function value method and the calculation of the comprehensive evaluation value, the nine cultivars could be classified into three categories. The cultivar with the highest comprehensive evaluation value of the mineral element content was O.C. The one with the lowest value was H2, which indicated that O.C is a suitable variety for popularization in rocky desert mountainous areas. Stepwise regression analysis concluded that P, K, Fe, Mn, and Cu were the indicators significantly influencing the mineral element content of macadamia nuts and fruits in rocky desert mountains.

Red pitaya (Hylocereus undatus) is an essential tropical fruit in China. To make more rational use of its processing, byproducts and fruit seeds, and the type, composition, and relative content of lipids in pitaya seed oil were analyzed by UPLC-TOF-MS/MS. The results showed that the main fatty acids in pitaya seed oil were linoleic acid 42.78%, oleic acid 27.29%, and palmitic acid 16.66%. The ratio of saturated fatty acids to unsaturated fatty acids to polyunsaturated fatty acids was close to 1:1.32:1.75. The mass spectrum behavior and fracture mechanism of four lipid components, TG 54:5|TG 18:1_18:2_18:2, were analyzed. In addition, lipids are an essential indicator for evaluating the quality of oils and fats, and 152 lipids were isolated and identified from pitaya seed oil for the first time, including 136 glycerides and 16 phospholipids. The main components of glyceride and phospholipids were triglycerides and phosphatidyl ethanol, providing essential data support for pitaya seed processing and functional product development.

Guizhou Province is one of the regions in China where macadamia is cultivated. The area is characterized by prominent karst landforms, with uneven distribution of precipitation and utilizable water resources, which poses significant challenges to macadamia production. To explore the effects of different drought levels on the anatomical structure and physiological characteristics of macadamia seedlings, and to reveal their adaptation mechanisms and regulatory responses to drought stress, this study established a drought stress experiment on O.C (Own Choice) macadamia seedlings. The seedlings were subjected to stress in a 25% PEG-6000 solution for 0 h (CK), 24 h, 36 h, 48 h, and 72 h, and cellular structural features of stems and leaves were measured, as well as physiological and biochemical indices. The results indicated that macadamia seedlings gradually exhibited dehydration and chlorosis with prolonged drought stress. At 72 h of drought stress, root water potential, leaf water potential, chlorophyll content, relative water content, and root activity decreased by 353%, 98%, 44%, 72%, and 79%, respectively. Leaf thickness, palisade tissue thickness, and spongy tissue thickness were reduced by 19%, 33%, and 29%, respectively. Stomatal density increased by 50%, while stomatal aperture, vessel diameter, and cell wall thickness significantly decreased. Photosynthesis was markedly impaired: Pn, Tr, Gs, WUE, Fv/Fm, qP, and ΦPSII declined by 73%, 25%, 67%, 64%, 0.23, 60%, and 84%, respectively, whereas Ci and qN increased by 107% and 11%, respectively. Cell membranes began to sustain damage after 24 h of drought stress, with electrolyte leakage and MDA content rising by 266% and 672%, respectively, at 72 h. Prolonged drought stress reduced IAA, CTK, and GA levels by 37%, 33%, and 16%, respectively, while ABA content increased by 48%. To counteract drought stress, seedlings activated osmotic adjustment and reactive oxygen species (ROS) scavenging mechanisms. Osmolyte content significantly increased with stress duration, reaching 61%, 73%, 697%, and 107% increments in SS, SP, Pro, and betaine at 72 h. Antioxidant enzyme activities initially rose, peaking at 24 h (SOD, POD, CAT, and APX increased by 132%, 288%, 110%, and 46%, respectively), then gradually declined. By 72 h, SOD and APX activities fell below control levels, while POD and CAT remained elevated. These findings demonstrate that under PEG-6000-simulated drought stress, macadamia seedlings alleviate damage by modifying leaf and stem cellular structures and activating antioxidant and osmotic adjustment mechanisms. This study provides a theoretical basis for understanding the physiological mechanisms of macadamia drought stress response.

Seed germination is a crucial developmental event in the plant life cycle. Proper germination significantly impacts the yield and quality. This study focuses on macadamia nuts, exploring the physiological, metabolic, and molecular biological characteristics during seed germination. The water content of macadamia seeds reached a peak in the seed imbibition stage, followed by a gradual decline. Key components such as fats, proteins, and soluble sugars decreased consistently. The enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione peroxidase (GPX) increased throughout seed germination, reaching peak levels in leaf growth stages. A total of 1523 metabolites and 13,035 differentially expressed genes (DEGs) were detected by transcriptomic and metabolomic analyses, among which 1320 were transcription factors. The transcriptome and metabolome integration analysis showed significant overlaps between DEGs and differential metabolites in pathways such as phenylpropanoid biosynthesis. Quercetin, trifolin, rutin, myricetin, and quercetin 3-beta-D-sophoroside may play important roles in seed germination. FG2 and CYP75A/CYP75B1 were key genes in the flavonoid pathway. Hormones such as auxin (IAA), cytokinin (CTK), gibberellin (GA), and abscisic acid (ABA) exhibited stage-specific changes during germination. This study provided important theoretical basis and practical guidance for optimizing seed germination rates and enhancing stress resistance capabilities.