Lifecycle of Dryocosmus kuriphilus Yasumatsu and Diversity and Importance of the Native Parasitoid Community Recruited in the Northern Region of Portugal.

In this work, the objective was to learn the life cycle of D. kuriphilus and the diversity of native parasitoids in the northern region of Portugal between 2017 and 2019. The places studied belonged to the regions of Entre-Douro-e-Minho, Beira Interior, and Trás-os-Montes. To achieve the proposed objectives, buds were collected for egg and larva observation, galls were collected for larva, pupa, and adult observation and monitoring, and emergency boxes were used to identify the fauna present in the galls. In this study, 92% of D. kuriphilus adults emerged between June and July, with emergences occurring until September. We also obtained adults in winter, so it is important to study, in future works, the hypothesis of this pest performing diapause. Regarding the study of native parasitoids, compared to other countries, the same families emerged, with good rates of natural parasitism, although with fluctuations over the years. In the three municipalities under study, 11 species were identified (Eupelmus azureus Ratzeburg, Eupelmus urozonus Dalman, Eurytoma brunniventris Ratzeburg, Megastigmus dorsalis (Fabricius), Ormyrus pomaceus (Geoffroy), Sycophila iracemae Nieves Aldrey, Sycophila variegata (Curtis), Sycophila biguttata (Swederus), Torymus flavipes (Walker), Torymus auratus (Mueller), and Torymus notatus (Walker)). The average parasitism rates varied between 1.92% and 10.68%.

Can Beauveria bassiana (Bals.-Criv.) Vuill. Control the Key Fruit Pests of the European Chestnut Tree, under Field Conditions?

The chestnut moth (Cydia splendana Hübner) and the chestnut weevil (Curculio elephas Gyllenhal) cause serious damage to European producers and companies that transform and market the chestnut. The objective of the present work was to evaluate, under field conditions, the possibilities of Beauveria bassiana (Bals.-Criv.) Vuill. to infect and kill the larvae of the two main carpophagous pests of European chestnut, in treatments directed at the soil. For this purpose, the surfaces of vases were sprayed with two concentrations of conidia/mL 5 × 107 (T1) and 1 × 108 (T2). The control (T0) was sprayed with distilled water. Larval mortality and infection were evaluated on five dates (D8 to D220). Confirmation of the fungus present in the larva was performed by molecular analysis. The results obtained are promising for the use of B. bassiana as a biological control agent against these key pests of the chestnut crop. There were no significant differences in mortality between the T1 and T2 modalities, however, they were significantly higher than the control. In the case of total mortality (dead and infected larvae), no significant differences were observed for C. elephas either. In the case of C. splendana, the T2 modality obtained better results in terms of total mortality.

Effect of relative humidity on the quality and safety of peeled almond kernels (Prunus dulcis Mill.) during simulated maritime transport/storage.

Long-term transport and storage of peeled almonds under unsuitable conditions may cause the product's rejection. To get knowledge in this topic, peeled almonds were stored at 25°C and 60, 70, and 80% relative humidity (RH). The maintenance of high RH (80%) caused some visual defects after 4 months. Even though the 60, 70, and 80% RH did not clearly affect the production of primary and secondary products formed in the lipid oxidation during the 6 months of storage, sometimes an increase in the values of the specific extinction at the wavelength of 268 nm (K268 ) was observed at 80% RH, suggesting the occurrence to some extent of secondary oxidation. Concerning microbial counts, the almonds stored at 60 and 70% RH presented a satisfactory microbial quality until 6 months; however, at 80% RH, the mold counts were higher than the reference values after 2 months. Several mycotoxins were detected at low levels, including aflatoxins B1 and G1, although some showed higher amounts at 80% RH. In general, it is recommended that almond producers and industrials should consider the use of low RH (< 80%) for maritime transport and long-term storage of almond kernels. PRACTICAL APPLICATION: High levels of relative humidity during storage/transport of almond kernels favor fungal growth, mycotoxin production, and secondary oxidation (rancidity). It is recommended to keep the almond kernels under low RH (< 80%) in maritime transport and long storage, especially in tropical countries.

Correction: Biological control of the Asian chestnut gall wasp in Portugal: Insights from a mathematical model.

[This corrects the article DOI: 10.1371/journal.pone.0254193.].

Biological control of the Asian chestnut gall wasp in Portugal: Insights from a mathematical model.

In recent years, the Asian gall wasp Dryocosmus kuriphilus has invaded chestnut trees and significantly affected the Portuguese chestnut production. Studies in other countries, such as Japan or Italy, have shown that the parasitoid Torymus sinensis can successfully achieve biological control of D. kuriphilus. Mathematical models help us to understand the dynamics of the interaction between the pest D. kuriphilus and its parasitoid T. sinensis and, consequently, they can help to implement measures that enhance crop pest management. In this work, the evolution of the density of D. kuriphilus and T. sinensis across time and space is studied through the numerical solution of models that include parameters based on observations made in Portugal. Simultaneous releases of the parasitoid are simulated at various locations and at different times. The results indicate that, in the case of a small and homogeneous orchard, biological control can be effective, but, in the case of extensive domains, the pest control is much more difficult to achieve. In order for biological control to be efficient, it is necessary to implement, in each chestnut-producing region, a collective strategy based on the annual monitoring of infestation levels.

Castanea sativa male flower extracts as an alternative additive in the Portuguese pastry delicacy "pastel de nata".

Replacing artificial additives by natural compounds is a current trend in the food industry. In addition to their preserving effect, naturally obtained ingredients often exhibit important levels of bioactivities. Generally, plant species represent better sources of natural ingredients, since their compounds are less prone to causing unpleasant taste or odour. Chestnut male flower (CMF) was reported to have high antioxidant and antimicrobial activities. Hence, it was tested as an alternative to potassium sorbate in the most treasured Portuguese delicacy: "pastel de nata". Different nutritional, chemical, physical and bioactive parameters were compared in two different periods: baking day and two days after baking. All samples presented similar nutritional and chemical profiles, but those added with CMF revealed higher contents of reducing agents and radical scavengers. Accordingly, the newly obtained formulation is expected to have better effects on consumers' health, maintaining the chemical characteristics, besides rendering a novel, economically profitable, application to CMF.

Development of a natural preservative obtained from male chestnut flowers: optimization of a heat-assisted extraction technique.

The aim of this work was to optimize the conditions for the extraction of phenolic compounds (PC) from male chestnut flowers using heat-assisted extraction in developing extracts rich in PC for potential industrial application as a natural ingredient. The study conditions of time (t), temperature (T), solvent (S, water-ethanol mixtures) and solid-to-liquid ratio (S/L) were optimized. The responses used were obtained from the quantification of the fourteen major individual PC identified by HPLC-DAD-ESI/MS (seven hydrolysable tannins and seven flavonoids). The recovery of hydrolysable tannins was higher than that of flavonoids, with trigalloyl-HHDP-glucoside being the major one. The conditions that maximized the PC content were t = 20.0 ± 37.7 min, T = 25.0 ± 5.7 °C, S = 0.0 ± 8.7% ethanol and S/L = 82.8 g L-1, producing an extract with 86.5 mg PC g-1 of extract. The results highlight the potential of valorising chestnut flower agro-residues as a productive source of PC for the development of bio-based ingredients for food/pharmaceutical/cosmeceutical industrial applications able to compete with synthetic compounds.

Ancient olive trees as a source of olive oils rich in phenolic compounds.

Olive oil phenolic compounds are receiving increased attention due to its influence on sensory characteristics and to scientific evidences of positive health effects. In this work, 28 ancient olive trees were selected and, during four consecutive seasons (2014-2017), oils were extracted and their phenolic fraction characterized. Hydroxytyrosol and tyrosol secoiridoids were the predominant groups, with contents between 32 and 496 mg of tyrosol equivalents/kg. Based on principal component analysis it could be concluded that the individual phenolic contents enabled the unsupervised grouping of olive oils by crop year. Furthermore, linear discriminant analysis allowed achieving sensitivities greater than 90%. It was shown that some specimens consistently allowed obtaining oils with high phenolic contents (≥500 mg tyrosol equivalents/kg). The identification of centenarian specimens for breeding based on their potential to produce oils with high levels of healthy compounds is of utmost interest, contributing to preserve the genetic heritage.

Selection of grapevine leaf varieties for culinary process based on phytochemical composition and antioxidant properties.

Grapevine leaves are an abundant sub-product of vineyards which is devalued in many regions. The objective of this work is to study the antioxidant activity and phytochemical composition of ten grapevine leaf varieties (four red varieties: Tinta Amarela, Tinta Roriz, Touriga Franca, and Touriga Nacional; and six white varieties: Côdega do Larinho, Fernão Pires, Gouveio, Malvasia Fina, Rabigato, and Viosinho) to select varieties to be used as food ingredients. White grapevine leaves revealed higher antioxidant potential. Malvasia Fina reported better antioxidant properties contrasting with Touriga Franca. Phenolic content varied between 112 and 150mgGAEg(-1) of extract (gallic acid equivalents), hydroxycinnamic acid derivatives and flavonols varied between 76 and 108mgCAEg(-1) of extract (caffeic acid equivalents) and 39 and 54mgQEg(-1) of extract (quercetin equivalents). Malvasia Fina is a good candidate for culinary treatment due to its antioxidant properties and composition in bioactive compounds.

Chestnut and lemon balm based ingredients as natural preserving agents of the nutritional profile in matured "Serra da Estrela" cheese.

Chestnut flowers, lemon balm plants and their decoctions were incorporated into "Serra da Estrela" cheese, to assess their potential to preserve its nutritional properties and provide new foodstuffs. The analyses were carried out after the normal ripening period of 1month and after 6months of storage. The most abundant nutrients were proteins and fats. The most abundant minerals were Ca and Na, while C16:0 and C18:1 were the main fatty acids. Saturated fatty acids were the most abundant, followed by the monounsaturated. Moisture seemed to be lower in the samples with the plants incorporated. The dried plants, when incorporated, seemed to be more efficient as preservers then the decoctions, although these better preserved the proteins. These plants can be regarded as promising natural preservers in foodstuffs cheese, given the preservation of key parameters and the slight impact on the nutritional value.

Bioactivity and phenolic composition from natural fermented table olives.

In the present work, the phenolic composition, and antioxidant and antimicrobial properties of twenty-four samples of naturally fermented table olives from the northeast of Portugal were evaluated. The analysis of phenolic composition was performed by HPLC/DAD, and ten compounds were identified, hydroxytyrosol, verbascoside derivate and hydroxytyrosol glycol being the most abundant. Total phenolic content varied between 2.37 and 64.17 µg mg(-1) of extract. The IC50 values from the antioxidant activity methods tested varied between 0.30 and 1.66 mg mL(-1) for reducing power, and between 0.13 and 0.83 mg mL(-1) for DPPH. The results obtained in the antioxidant activity were extremely significantly correlated with the main phenolic compounds as well as with the total phenolic content. A principal component analysis allowed grouping the samples according to their phenolic composition and antioxidant potential. Table olive extracts were able to inhibit some pathogenic microorganisms, mainly Gram-positive bacteria. Higher antimicrobial inhibition was recorded in the extracts rich in phenolic compounds and higher antioxidant potential.

Chestnut flowers as functionalizing agents to enhance the antioxidant properties of highly appreciated traditional pastry.

Some studies have proven the antioxidant and antimicrobial potency of chestnut flowers both in the raw matrix and after extraction, and the consumption of their decoctions has been related to beneficial effects towards health. In recent years, due to controversy and ambiguous legislation of chemical conservatives, plant extracts have been successfully used as functionalizing agents in different matrixes by displaying their various beneficial effects towards the foodstuff and/or the consumer. In this paper, decoctions of chestnut flowers as well as the dried flower were added to Portuguese traditional cakes that were then stored for 15 and 30 days, after which they were analysed for their antioxidant potential. The results were analysed by means of a 2 way ANOVA and a linear discriminant analysis, concluding that storage time had a slightly higher influence on alteration of the antioxidant activity. DPPH and TBARS were the most improved parameters, regardless of the concentration added.

Castanea sativa Mill. Flowers amongst the most powerful antioxidant matrices: a phytochemical approach in decoctions and infusions.

Infusions and decoction of chestnut tree flowers have been used for different medical purposes, but their phytochemical profile and antioxidant activity are still mostly unknown. Herein, decoctions and infusions of flowers from the two most appreciated chestnut cultivars (longal and judia) in Trás-os-Montes, Portugal, were prepared and characterized with regard to their content in free sugars, organic acids, and phenolic compounds, such as flavonoids and hydrolyzable tannins, and their antioxidant activity. Overall, the decoction of the cultivar judia was the sample with both the highest quantity of flavonoids and antioxidant activity. The phenolic compound with the highest abundance in all samples was trigalloyl-HHDP-glucoside, followed by pentagalloyl glucoside. The sample with the highest quantity of total phenolic compounds was judia infusion, closely followed by longal decoction, which also gave the highest quantities of ellagitannins. Regarding sugars and organic acids, the profiles were more similar. These results corroborate ancestral claims of the health benefits of infusions and decoctions of chestnut flowers.

Analysis of organic acids in electron beam irradiated chestnuts (Castanea sativa Mill.): Effects of radiation dose and storage time.

Since 2010, methyl bromide, a widely used fumigant was banned from the European Union under the Montreal Protocol guidelines, due to its deleterious effects on health and risk to the environment. Since then, many alternatives for chestnut conservation have been studied (hot water dip treatment being the most common), among them, electron beam irradiation has been proposed as being a safe, clean and cheap alternative. Herein, the effects of this radiation at different doses up to 6kGy and over storage up to 60days in the amounts and profile of nutritionally important organic acids were evaluated. Chestnuts contained important organic acids with quinic and citric acids as main compounds. Storage time, which is traditionally well accepted by consumers, caused a slight decrease on quinic (13-9mg/g), ascorbic (1.2-0.8mg/g), malic (5-4mg/g), fumaric (0.4-0.3mg/g) and total organic (33-26mg/g) acids content. Otherwise, irradiation dose did not cause appreciable changes, either individually or in total (28-27mg/g) organic acid contents. Electron beam irradiation might constitute a valuable alternative for chestnut conservation.

Comparative effects of gamma and electron beam irradiation on the antioxidant potential of Portuguese chestnuts (Castanea sativa Mill.).

Chestnuts (Castanea sativa Mill.) are widely consumed all over the world, and have been recently studied for their antioxidant potential. The present study reports the effect of e-beam and gamma radiation (doses of 0, 0.5, 1 and 3 kGy) on the antioxidant potential of Portuguese chestnuts. Irradiation might be an alternative preservation method, since Methyl Bromide, a widely used fumigant, was banished by the European Union in 2010 due to its toxicity. The antioxidant activity was evaluated through 2,2-diphenyl-1-pycrylhydrazyl (DPPH) free radical scavenging activity assay, reducing power by the Ferricyanide/Prussian blue assay, and lipid peroxidation inhibition by ß-carotene/linoleate and thiobarbituric acid reactive substances (TBARS) assays. The analysis of total phenolics and flavonoids was performed by spectrophotometric assays. Irradiated samples preserved total phenolics content (but not flavonoids) and revealed higher antioxidant activity (lower EC50 values) than the control samples. The most indicated doses to maintain antioxidants content, and to increase antioxidant activity were 1 and 3 kGy for electron beam and gamma radiation, respectively.

Effects of electron-beam radiation on nutritional parameters of Portuguese chestnuts (Castanea sativa Mill.).

Chestnuts are a widely consumed fruit around the world, with Portugal being the fourth biggest producer in Europe. Storage of these nuts is an important step during processing, and the most widely used fumigant was banned in the European Union under the Montreal Protocol because of its toxicity. Recently, radiation has been introduced as a cheap and clean conservation method. Previous studies of our research group proved that γ radiation had no negative effect on the nutritional value of chestnuts; in fact, storage time had a much bigger influence on the chestnut quality. In the present study, we report the effect of a less ionizing radiation, electron beam, with doses of 0, 0.5, 1, 3, and 6 kGy in the nutritional value of chestnuts (ash, energy, fatty acids, sugars, and tocopherols), previously stored at 4 °C for 0, 30, and 60 days. The storage time seemed to reduce fat and energetic values but reported a tendency for higher values of dry matter. With regard to fatty acids, there was a higher detected quantity of C20:2 in non-irradiated samples and four fatty acids were only detected in trace quantities (C6:0, C8:0, C10:0, and C12:0). γ-Tocopherol decreased during storage time but did not alter its quantity for all of the radiation doses (as like α-, ß-, and δ-tocopherol); in fact, these compounds were present in higher concentrations in the irradiated samples. Sucrose and total sugars were lower in non-irradiated samples, and raffinose was only detected in irradiated samples. Electron-beam irradiation seems to be a suitable methodology, because the effects on chemical and nutritional composition are very low, while storage time seems to be quite important in chestnut deterioration.

Effects of gamma radiation on the biological, physico-chemical, nutritional and antioxidant parameters of chestnuts - a review.

Gamma radiation has been used as a post-harvest food preservation process for many years. Chestnuts are a seasonal product consumed fresh or processed, and gamma irradiation emerged recently as a possible alternative technology for their post-harvest processing, to fulfil the requirements of international phytosanitary trade laws. After harvest and storage, several problems may occur, such as the presence of infestations and development of microorganisms, namely rotting and fungi. These diminish the quality and safety of the product, decreasing the yield along the production chain. In fruits, gamma irradiation treatment is for two main purposes: conservation (ripening delay) and insect disinfestation (phytosanitary treatment). In this review, the application of gamma irradiation to chestnuts is discussed, including production data, the irradiated species and the effects on biological (sprouting, rotting, respiration rate, insects, worms and fungi), physico-chemical (color, texture, and drying rate), nutritional (energetic value, proteins, sugars and fatty acids) and antioxidant (tocopherols, ascorbic acid, phenolics, flavonoids and antioxidant activity) parameters. These changes are the basis for detecting if the food product has been irradiated or not. The validation of standards used for detection of food irradiation, as applied to chestnuts, is also discussed.

Influence of spike lavender (Lavandula latifolia Med.) essential oil in the quality, stability and composition of soybean oil during microwave heating.

Lipids oxidation is one of the main factors leading to quality losses in foods. Its prevention or delay could be obtained by the addition of antioxidants. In this sense the present work intend to monitor the protective effects of Lavandula latifolia essential oil during soybean oil microwave heating. To achieve the proposed goal quality parameters (free acidity, peroxide value, specific coefficients of extinction and ΔK), fatty acids profile, tocopherols and tocotrienols composition, antioxidant activity and oxidative stability were evaluated in soybean oil with and without spike lavender essential oils (EO) submitted to different microwave heating exposure times (1, 3, 5, 10 and 15 min; 1000 Watt) with a standard domestic microwave equipment. Microwave heating induced severe quality and composition losses, mainly above 3 min of microwave heating, regardless the sample tested. However, spike lavender EO addition counteracts the oxidation comparatively to control oils, by presenting enhanced values in quality parameters. A higher protection in unsaturated fatty acids loss was also observed as well as a higher antioxidant activity and oxidative stability. The microwave heating effects were clearly different in the samples with essential oils addition, allowing discrimination from plain soybean oils by a principal component analysis, being also capable to discriminate the different heating times tested within each sample.

Fungal diversity associated to the olive moth, Prays Oleae bernard: a survey for potential entomopathogenic fungi.

Olive production is one of the main agricultural activities in Portugal. In the region of Trás-os-Montes, this crop has been considerably affected by Prays oleae. In order to evaluate the diversity of fungi on Prays oleae population of Trás-os-Montes olive orchards, larvae and pupae of the three annual generations (phyllophagous, antophagous and carpophagous) were collected and evaluated for fungal growth on their surface. From the 3,828 larvae and pupae, a high percentage of individuals exhibited growth of a fungal agent (40.6%), particularly those from the phyllophagous generation. From all the moth generations, a total of 43 species from 24 genera were identified, but the diversity and abundance of fungal species differed between the three generations. Higher diversity was found in the carpophagous generation, followed by the antophagous and phyllophagous generations. The presence of fungi displaying entomopathogenic features was highest in the phyllophagous larvae and pupae, with Beauveria bassiana as the most abundant taxa. The first report of Beauveria bassiana presence on Prays oleae could open new strategies for the biocontrol of this major pest in olive groves since the use of an already adapted species increases the guarantee of success of a biocontrol approach. The identification of antagonistic fungi able to control agents that cause major olive diseases, such as Verticillium dahliae, will benefit future biological control approaches for limiting this increasingly spreading pathogen.

Chemical characterization of "alcaparras" stoned table olives from northeast Portugal.

Commercial stoned table olives named "alcaparras" from Trás-os-Montes (Portugal) were chemically characterized. During three consecutive years (2004-2006) 30 samples (10 per year) were examined for their nutritional value (moisture, crude protein, total fat, ash, carbohydrates, and energy), with a detailed report of the fatty acids and tocopherols composition. Water was the major constituent (72.5 ± 5.5%), followed by fat (14.6 ± 5.1%). The average amount of protein and ash were 1.1% and 3.4%, respectively, reporting unusual ash values for table olives, related to the technological process. One hundred grams of fresh stoned table olives presented an average energetic value of 156 kcal, lower than most table olives. The lipids are rich in oleic acid (average of 77.7 ± 2.0%), followed by palmitic acid and linoleic acid. Samples showed an average of total tocopherols of 1.2 mg/100 g of fresh weight, being α-tocopherol the most abundant. Table olives are important sources of MUFA, as olive oil, recognized as a preventive factor in diseases in which free radicals are implicated, complemented by the amounts of vitamin E, with both antioxidant and vitamin action.