Spatio-temporal Spread of Abnormal Vertical Growth of Macadamia in Australia Informs Epidemiology.
Australian macadamia production is threatened by a disorder known as abnormal vertical growth (AVG), for which the aetiology is unknown. AVG is characterized by vigorous upright growth and reduced lateral branching, flowering and nut set that results in over 70% yield loss annually. Six commercial macadamia orchards were surveyed in 2012 and again in 2018 to examine spatio-temporal dynamics of the epidemic. Data were subjected to point-pattern and geostatistical analyses. AVG incidence of all orchards showed better fit to beta-binomial distribution than binomial distribution. AVG incidence level of orchards varied between 5% and 47% in 2012, and 13% and 55% in 2018. AVG spread at a slow pace in all orchards, averaging at about 2% increase in disease incidence per annum. Spatial patterns of AVG were highly aggregated on both survey years by a number of tests at different scales and spread was mainly between neighbouring trees in a row or trees that were opposite to each other in different rows. Semivariograms showed large range values (ca. 15 - 120), indicating aggregation of AVG-affected trees beyond quadrat levels. Furthermore, clusters of disease were mainly at the edge of the orchard on the first survey date and the disease progressed towards the centre of the orchard over time. It is concluded that AVG is caused by an infectious agent, and based on patterns of spread, we hypothesise that spread is facilitated by root grafting or root-to-root contact. Furthermore, a vascular-limited pathogen could be involved that modulates plant hormone production.
Effect of Drying Temperature and Exposure Times on Aspergillus Flavus Growth and Aflatoxin Production on Artificially Inoculated Hazelnuts.
Aspergillus flavus may colonise hazelnuts and produce aflatoxins in field and during storage. The main purpose of this study was to investigate the influence of drying temperature and exposure times on the viability and ability of A. flavus to produce aflatoxins during the drying process and storage. Hazelnuts were inoculated with A. flavus and dried at different temperatures to reach 6% moisture content and a w 0.71, a commercial requirement to avoid fungal development and aflatoxin contamination. Hazelnuts were dried at 30, 35, 40, 45, and 50 °C and subsequently stored at 25 °C for 14 days. After drying at 30, 35 and 40 °C, an increased number of A. flavus was evident, with the highest concentration at 35 °C (6.1 ± 2.4 x10 6 A. flavus CFU/g). At these temperatures, aflatoxins were detected only at 30 °C and 35 °C. Aflatoxins, however, were higher after drying at 30 °C with a concentration of 1.93 ± 0.77 μg/g for aflatoxin B1 (AFB1) and 0.11 ± 0.04 μg/g for aflatoxin B2 (AFB2). After 14 days of storage, the highest A. flavus concentration and the highest level of mycotoxins were detected in samples treated at 35 °C (8.2 ± 2.1 x10 7 A. flavus CFU/g, 9.30 ± 1.58 μg/g and 0.89 ± 0.08 μg/g for AFB1 and AFB2, respectively). In hazelnuts dried at 45 °C or 50 °C no aflatoxins were found both after drying and storage, and a reduction of A. flavus viable conidia was observed, suggesting that a shorter and warmer drying is essential to guarantee the nut safety. The lowest temperature that guarantees the lack of aflatoxins should be selected to maintain the organoleptic quality of hazelnuts. Therefore, 45°C should be the recommended drying temperature to limit A. flavus growth and aflatoxin contamination on hazelnuts.
Does ‘activating’nuts affect nutrient bioavailability?.
Claims in the lay literature suggest soaking nuts enhances mineral bioavailability. Research on legumes and grains indicate soaking reduces phytate levels, however, there is no evidence to support or refute these claims for nuts. We assessed the effects of different soaking regimes on phytate and mineral concentrations of whole and chopped almonds, hazelnuts, peanuts, and walnuts. The treatments were: 1. Raw; 2. soaked for 12 h in salt solution; 3. soaked for 4 h in salt solution; 4. soaked for 12 h in water. Phytate concentrations were analysed using high-performance liquid chromatography (HPLC) and minerals by inductively coupled plasma mass spectrometry (ICP-MS). Differences in phytate concentrations between treated and untreated nuts were small, ranging from -12% to +10%. Overall, soaking resulted in lower mineral concentrations, especially for chopped nuts, and did not improve phytate:mineral molar ratios. This research does not support claims that 'activating' nuts results in greater nutrient bioavailability.
Nutritional, Microbial, and Allergenic Changes during the Fermentation of Cashew ‘Cheese’ Product Using a Quinoa-Based Rejuvelac Starter Culture.
Fermentation has been applied to a multitude of food types for preservation and product enhancing characteristics. Interest in the microbiome and healthy foods makes it important to understand the microbial processes involved in fermentation. This is particularly the case for products such as fermented cashew (Anacardium occidentale). We hereby describe the characterisation of cashew samples throughout an entire fermentation production process, starting at the quinoa starter inoculum (rejuvelac). The viable bacterial count was 108 -109 colony forming units/g. The nutritional composition changed marginally with regards to fats, carbohydrates, vitamins, and minerals. The rejuvelac starter culture was predominated by Pediococcus and Weissella genera. The 'brie' and 'blue' cashew products became dominated by Lactococcus, Pediococcus, and Weissella genera as the fermentation progressed. Cashew allergenicity was found to significantly decrease with fermentation of all the end-product types. For consumers concerned about allergic reactions to cashew nuts, these results suggested that a safer option is for products to be made by fermentation.
A Targeted Approach by High Resolution Mass Spectrometry to Reveal New Compounds in Raisins.
Raisins are dried grapes mostly obtained from cultivars of Vitis vinifera L. and are extensively consumed worldwide. They are rich in bioactive compounds such as polyphenols, which are associated with a broad range of health benefits. The aim of the present study was to compare the phenolic profiles of three different raisin varieties (Thompson seedless, Muscat, and sultanas). Total polyphenols (TPs) were evaluated by the Folin-Ciocalteu (F-C) assay and significant differences were observed among all raisin varieties. Furthermore, liquid chromatography coupled with electrospray ionization hybrid linear ion trap quadrupole-Orbitrap-mass spectrometry (LC/ESI-LTQ-Orbitrap-MS) was employed for the comprehensive identification of phenolic constituents. A total of 45 compounds were identified, including hydroxybenzoic and hydroxycinnamic acids, flavanoids, flavonoids, flavonols, flavones, and stilbenoids. The three varieties of raisins showed a similar phenolic profile, although the highest number of phenolic compounds was identified in Muscat raisins owing to the proanthocyanidins extracted from their seeds, while stilbenoids were not detected in the Thompson variety.
Aspergillus, Penicillium and Cladosporium species associated with dried date fruits collected in the Perugia (Umbria, Central Italy) market.
A total of 20 dried date samples, chosen as representative among those available on the Perugia (Umbria, Central Italy) market, were analyzed for the possible occurrence of fungal species and related contamination by fungal secondary metabolites. Twenty-six isolates, representative of the total mycobiota, were obtained and morphologically identified as belonging to the genera Aspergillus, Penicillium and Cladosporium. Inside each genus, molecular characterization (by partial sequencing of ITS region and/or β-tubulin and calmodulin regions for Aspergillus and Penicillium isolates or actin region for Cladosporium isolates) and in vitro mycotoxigenic profile characterization (by LC-MS/MS analysis) showed the presence of the following species: A. flavus, A. tubingensis, P. brevicompactum, P. chrysogenum, P. crustosum, P. glabrum, P. solitum, P. venetum, C. cladosporioides, C. limoniforme and C. halotolerans, with A. tubingensis as the prevalent species and P. crustosum, P. solitum, P. venetum and C. limoniforme first reported here on dates. Date packaging and format showed an effect on the incidence of isolated fungi, with the lowest incidence recovered from whole dates and in hermetic bag packaging. These findings can be useful both for dried dates producers and consumers, guiding them towards choices of packaging and format with a lower risk of mycotoxigenic species presence. However, no fungal metabolites were detected in the dried date samples analyzed, which were therefore regarded as safe for human consumption, underlining the absence of correspondence between fungal isolation and mycotoxin contaminations.
Advances in Crop Improvement and Delivery Research for Nutritional Quality and Health Benefits of Groundnut (Arachis hypogaea L.).
Groundnut is an important global food and oil crop that underpins agriculture-dependent livelihood strategies meeting food, nutrition, and income security. Aflatoxins, pose a major challenge to increased competitiveness of groundnut limiting access to lucrative markets and affecting populations that consume it. Other drivers of low competitiveness include allergens and limited shelf life occasioned by low oleic acid profile in the oil. Thus grain off-takers such as consumers, domestic, and export markets as well as processors need solutions to increase profitability of the grain. There are some technological solutions to these challenges and this review paper highlights advances in crop improvement to enhance groundnut grain quality and nutrient profile for food, nutrition, and economic benefits. Significant advances have been made in setting the stage for marker-assisted allele pyramiding for different aflatoxin resistance mechanisms-in vitro seed colonization, pre-harvest aflatoxin contamination, and aflatoxin production-which, together with pre- and post-harvest management practices, will go a long way in mitigating the aflatoxin menace. A breakthrough in aflatoxin control is in sight with overexpression of antifungal plant defensins, and through host-induced gene silencing in the aflatoxin biosynthetic pathway. Similarly, genomic and biochemical approaches to allergen control are in good progress, with the identification of homologs of the allergen encoding genes and development of monoclonal antibody based ELISA protocol to screen for and quantify major allergens. Double mutation of the allotetraploid homeologous genes, FAD2A and FAD2B, has shown potential for achieving >75% oleic acid as demonstrated among introgression lines. Significant advances have been made in seed systems research to bridge the gap between trait discovery, deployment, and delivery through innovative partnerships and action learning.
Effect of post inoculation drying procedures on the reduction of Salmonella on almonds by thermal treatments.
Since two outbreaks of salmonellosis were linked to the consumption of almonds in 2001 and 2004, the study of pathogen inactivation kinetics in almonds has been encouraged, often by conducting inoculated challenge studies. The inoculation method could affect the results of such challenge studies, because of the possible increase of moisture on the almonds resulting from a wet inoculation procedure, which may result in a potential overestimation of the effectiveness of treatments used to pasteurize almonds in industrial settings. Salmonella enterica serotype Enteritidis phage type 30 (PT30) isolated from an almond-linked outbreak was inoculated on nonpareil almonds and dried by accelerated (drying the inoculated almonds at 37 °C for 12 h) and conventional (drying inoculated almonds overnight at room temperature) drying methods, before treating the almonds with hot water (blanching) at 88 °C or hot oil (oil roasting) at 127 °C. The Weibull model explained the death of this pathogen on almonds better than log-linear model for oil roasting, whereas both log-linear and Weibull models were similarly effective for blanching. For blanching, the D values for Salmonella Enteritidis PT30 were 12.7 and 10.7 s with accelerated and conventional drying, respectively. For oil roasting, the b-values were 4.59 and 4.18 s with accelerated and conventional drying, respectively. Based on the models, it was concluded that the accelerated drying process resulted in a significantly smaller reduction in Salmonella Enteritidis PT30 on almonds in comparison to conventional drying for both blanching and roasting. Although conventional drying led to significantly lower D or b - values (depending on the model), this difference is not likely to affect the current processing parameters used by the almond industry.
Genome-wide association studies for yield component traits in a macadamia breeding population.
Background: Breeding for new macadamia cultivars with high nut yield is expensive in terms of time, labour and cost. Most trees set nuts after four to five years, and candidate varieties for breeding are evaluated for at least eight years for various traits. Genome-wide association studies (GWAS) are promising methods to reduce evaluation and selection cycles by identifying genetic markers linked with key traits, potentially enabling early selection through marker-assisted selection. This study used 295 progeny from 32 full-sib families and 29 parents (18 phenotyped) which were planted across four sites, with each tree genotyped for 4113 SNPs. ASReml-R was used to perform association analyses with linear mixed models including a genomic relationship matrix to account for population structure. Traits investigated were: nut weight (NW), kernel weight (KW), kernel recovery (KR), percentage of whole kernels (WK), tree trunk circumference (TC), percentage of racemes that survived from flowering through to nut set, and number of nuts per raceme. Results: Seven SNPs were significantly associated with NW (at a genome-wide false discovery rate of < 0.05), and four with WK. Multiple regression, as well as mapping of markers to genome assembly scaffolds suggested that some SNPs were detecting the same QTL. There were 44 significant SNPs identified for TC although multiple regression suggested detection of 16 separate QTLs. Conclusions: These findings have important implications for macadamia breeding, and highlight the difficulties of heterozygous populations with rapid LD decay. By coupling validated marker-trait associations detected through GWAS with MAS, genetic gain could be increased by reducing the selection time for economically important nut characteristics. Genomic selection may be a more appropriate method to predict complex traits like tree size and yield.
Allergen Removal and Transfer Using Wiping and Cleaning Methods in Retail and Food Service Establishments.
Preventing the transfer of allergens from one food to another via food-contact surfaces in retail food environments is an important aspect of retail food safety. Existing recommendations for wiping and cleaning food-contact surfaces is mainly focused on preventing microorganisms such as bacteria and viruses from contaminating foods. The effectiveness of these wiping and cleaning recommendations for preventing the transfer of food allergens in retail and food service establishments remains unclear. This project investigated: 1) allergen removal from surfaces by wiping with paper wipes, terry cloths and alcohol/quaternary ammonium chloride (quat) sanitizing wipes; 2) cleaning of allergen-contaminated surfaces using a wash-rinse-sanitize-air dry procedure; and 3) allergen transfer from contaminated wipes to multiple surfaces. Food-contact surfaces (stainless steel, textured plastic and maple wood) were contaminated with peanut-, milk- and egg-containing foods, and subjected to various wiping and cleaning procedures. For transfer experiments, dry paper wipes or wet cloths contaminated with allergenic foods were wiped on four surfaces of the same composition. Allergen-specific lateral flow devices were used to detect the presence of allergen residues on wiped or cleaned surfaces. While dry wipes and cloths were not effective for removing allergenic foods, terry cloths pre-soaked in water or sanitizer solution, use of multiple quat wipes, and the wash-rinse-sanitize-air dry procedure were effective in allergen removal from surfaces. Allergens present on dry wipes were transferred to wiped surfaces. In contrast, minimal or no allergen transfer to surfaces was found when allergen-contaminated terry cloths were submerged in sanitizer solution prior to wiping surfaces. The full cleaning method (wash-rinse-sanitize-air dry) and soaking the terry cloth in sanitizer solution prior to wiping were effective at allergen removal and minimizing allergen transfer.