Main Sugar Research Articles

Drought resistance evaluation of sugar beet germplasms by response of phenotypic indicators

ABSTRACT Sugar beet is a main sugar crop worldwide that often faces drought stress. The identification of drought tolerance of sugar beet germplasms is beneficial for breeding, but the research about it has been rarely reported. In this study, the drought tolerance of germplasms 92005-1, 94002-2 and 92021-1-1 was tested under simulated conditions. Seven days and 9% PEG treatment were the optimal conditions for evaluation, under which more phenotypic indicators showed significant difference in drought tolerance coefficient. The objective weighting and membership function method were established for evaluating the drought tolerance of different sugar beet germplasms. Drought stress decreased the biomass of leaves and roots of sugar beet germplasms. The drought-sensitive germplasm responded faster for leaf weight, root weight, plant height and root length. These indicators declined more significantly under long-term and severe stress. Increasing the root–shoot ratio and proline content were universal strategies of sugar beet germplasms to overcome drought stress. The drought-tolerant germplasms held higher peroxidase activity and better ability to scavenge reactive oxygen for preventing the damage.

Identification of a stable major sucrose-related QTL and diagnostic marker for flavor improvement in peanut.

An InDel marker closely linked with a major and stable quantitative trait locus (QTL) on chromosome A08, qSUCA08.2, controlling sucrose content will benefit peanut flavor improvement. Sucrose is the main soluble sugar in mature peanut kernel, and its content is a key determinant of flavor. However, the genetic basis of sucrose content in peanut remains poorly understood, which limits the progress of flavor improvement. In the present study, two genomic regions (qSUCA08a and qSUCB06a) for sucrose content on chromosomes A08 and B06 were identified by QTL-seq in a RIL population derived from a cross between Zhonghua 10 and ICG 12625. In the interval of qSUCB06a, QTL qSUCB06.2 was detected through QTL mapping in a single environment. The qSUCA08a was further dissected into 3 adjacent genomic regions using linkage analysis including a major QTL qSUCA08.2 explaining 5.43-17.84% phenotypic variation across five environments. A 61-bp insertion at position 35,099,320 in the higher sucrose parent ICG 12625 was found in qSUCA08.2. An InDel marker SUC.InDel.A08 based on the insertion/deletion polymorphism was developed and validated within a natural population containing 172 peanut cultivars in two environments. The mean sucrose content of 93 cultivars with ICG 12625 allele was significantly higher than that of 79 cultivars with Zhonghua 10 allele. The qSUCA08.2 corresponding to a 2.11Mb interval harbored 110 genes. Among these genes, a total of 19 genes were considered as candidate genes including 5 non-synonymous mutation genes and 14 differentially expressed genes during seed development. These results provide new insights into the genetic basis of sucrose regulation in peanut and benefit the breeding program for developing new varieties with excellent flavor.

Comparative assessment of physicochemical, structural and functional properties of dietary fiber extracted from mango (Mangifera indica L.) and soursop (Annona muricata) peels

The potential of soursop, a less well-known tropical fruit, was assessed as a source of dietary fiber (DF) and compared to mango. After optimizing the conditions to maximize the extraction yield of soluble and insoluble DF, their structural, physicochemical, and functional properties were evaluated. The results showed that soursop excelled in total and insoluble DF content (50 % higher than mango). The antioxidant response and reducing sugar content obtained for soursop were significantly higher than in mango. Yet, the insoluble fraction in both fruits was characterized by higher antioxidant activity and phenolic content. The chemical composition of both fruits revealed that glucose and potassium were the main sugar and mineral, respectively. Lactic, formic, and acetic acids were the main short-chain fatty acids produced after in vitro colonic fermentation with Lacticaseibacillus casei and Lacticaseibacillus rhamnosus, and negligible amounts of butyric, propionic, and valeric acids were detected after 48-h-fermentation, independent of the fruit. Soursop is a promising rich source of DF that can be used together with mango to develop and enhance foods' textural and nutritional characteristics.

The grapevine metabolite profile of phloem sap is modified by flavescence dorée

Flavescence dorée (FD) has been recorded in French vineyards since the mid-1950s; it has rapidly become a major threat to vineyard survival in different European grape-growing areas. Infection by the phytoplasma ‘Candidatus Phytoplasma vitis’ causes leaf chlorosis and disturbs primary and secondary core metabolic pathways; it can also occlude sieve plates, therefore affecting normal solute transport through the phloem. Thus, in the present study we hypothesised that the metabolomic fingerprint of the phloem sap changes in FDp-infected vines. The metabolome of the phloem sap collected by centrifugation from the bark of the stem of healthy and infected vines (cv. ‘Loureiro’) was profiled by ESI-HRMS at two snapshot time points: E-L 33 (grape berry still hard and green) and E-L 38 (grape berry at maturity). An untargeted analysis of the phloem sap enabled the identification of 476 metabolites, whereas the targeted analysis focused on eight main classes, namely acids, sugar and polyols, amino acids, phenolic acids, hormones, vitamins and N compounds, as well as on several minor classes like fatty acids, phenols or diols. Depending on the developmental stage of the vine, major differences were observed in the composition of cv. ‘Loureiro’ phloem sap in response to FD infection in terms of sugar, organic acid and amino acid content; furthermore, compounds involved in plant defense, such as salicylic acid, ABA, vitamin C and gallic acid also significantly changed. Overall, these results have contributed towards increasing knowledge about the complex interactions between vine and FD phytoplasma.

Targeted multi-platform metabolome analysis and enzyme activity analysis of kiwifruit during postharvest ripening.

Kiwifruit is a climacteric fruit, in which the accumulation of flavor substances mainly occurs at the postharvest ripening stage. However, the dynamic changes in metabolite composition remain poorly understood. Here, targeted multi-platform metabolome analysis based on GC-MS and UPLC-MS/MS and enzyme activity analysis were performed at different postharvest ripening stages of kiwifruit. A total of 12 soluble sugars and 31 organic acids were identified. The main soluble sugars are sucrose, glucose and fructose, which exhibited similar variation tendencies along with the extension of ripening. The main organic acids are citric acid, quinic acid and malic acid, which showed different variation patterns. A total of 48 energy metabolites were identified, which were classified into two groups based on the content variation. The content of substances related to the respiratory metabolic pathway decreased gradually along with postharvest ripening, and there was obvious accumulation of downstream products such as amino acids at the late ripening stage. A total of 35 endogenous hormones were identified, among which seven cytokinins were highly accumulated at the later stage of softening. We further investigated the dynamic changes in the activities of 28 ripening-related enzymes. As a result, the activities of 13 enzymes were highly correlated with changes in starch, total pectin, and soluble sugars, and those of seven enzymes were closely associated with the change in firmness. In conclusion, this study comprehensively describes the dynamic changes in soluble sugars, organic acids, hormones, energy substances, and ripening-related enzyme activities during kiwifruit postharvest ripening, and provides a theoretical basis for the postharvest quality improvement of kiwifruit.

Hyaluronidase-inhibiting Polysaccharide from Caulerpa lentillifera.

Algal sulfated polysaccharides are known to be effective hyaluronidase inhibitors. We evaluated hyaluronidase inhibitory activity of sulfated polysaccharide (SP) from Caulerpa lentillifera. Results showed that SP with IC50 of 163 µg/mL appears to allosterically inhibit the hyaluronidase activity. Main sugar composition and sulfate content of SP was estimated to be Gal, Glc, Xyl, Man, uronic acids, and sulfate in the weight percent of 27.7: 28.9: 14.6: 22.5: 3.4: 21.7. We modified the SP by desulfation and partial hydrolysis with trifluoroacetic acid (TFA) to investigate the effect of sulfate content and molecular weight on inhibition. Hyaluronidase inhibitory activity of desulfated SP, 0.1 M TFA-hydrolyzed SP and 0.5 M TFA-hydrolyzed SP were significantly lower than that of native SP, revealing that sulfate content or molecular weight is important for hyaluronidase inhibition.

Characterization of Pekmez Samples Produced with Different Fruits According to Sugar, Organic Acid, Antioxidant Activities, and Moisture Contents

Chemical properties of grape, cranberry, blueberries, pomegranate, black mulberry, juniper, and carob pekmez samples were investigated in this study. Capillary electrophoresis was used to assess the organic acids and sugar levels of pekmez samples. The two main sugars were found to be as glucose and fructose. Juniper pekmez has the lowest sugar with 22.6 g /100 g glucose and 20.1 g /100 g fructose. Black mulberry (35.6 g/100 g) has the highest glucose whereas grape (45.8 g /100 g) includes the highest fructose. Each pekmez samples included 8 organic acids which are oxalic, tartaric, malic, citric, succinic, acetic, lactic, and gluconic acid. 1,1-diphenyl-2-picryl-hydrazil (DPPH) technique was applied for testing the antioxidant activities. Carob pekmez scavenged DPPH the most with 96.28% inhibition value. The other pekmez samples have inhibited DPPH with the values ranging between 58.04% (cranberry) to 90.16 (juniper). The samples' total phenolic levels ranged from 265 mg GAE/g (blueberry) to 1070 mg GAE/g (grape). Moisture contents were measured using a moisture analyzer. Cranberry pekmez (19.06%) and grape pekmez (12.24%) have significantly the highest moisture compared to other samples changing between 2.41% and 5.10%.

Influence of Cultivar and Turbidity on Physicochemical Properties, Functional Characteristics and Volatile Flavor Substances of Pomelo Juices

In this study, the influences of pomelo cultivars on physicochemical properties, functional characteristics, and volatile compounds of juices were investigated. Among these six varieties, the highest juice yield (73.22%) was obtained in grapefruit. Sucrose and citric acid were the main sugar component and organic acid of pomelo juices, respectively. The results showed that the cv. Pingshanyu pomelo juice and grapefruit juice had the highest sucrose (87.14 g L-1, 97.69 g L-1) and citric acid content (14.49 g L-1, 13.7 g L-1), respectively. Moreover, the naringenin was the main flavonoid of pomelo juice. Additionally, the total phenolics, total flavonoids, and ascorbic acid concentrations of grapefruit and cv. Wendanyu pomelo juice were higher than those of other varieties of pomelo juices. Furthermore, 79 volatile substances were identified from the juices of six pomelo cultivars. Hydrocarbons were the predominant volatile substances, and the limonene was the characteristic hydrocarbon substance of pomelo juice. In addition, the pulp content of pomelo juice also presented great effects on its quality and volatile compounds composition. Compared to low pulp juice, the corresponding high pulp juice had higher sucrose, pH, total soluble solid, acetic acid, viscosity, bioactive substances and volatile substances. The effects of cultivars and variation in turbidity on juice are highlighted. It is useful for pomelo breeders, packers and processors to understand the quality of the pomelo they are working with. This work could provide valuable information on selecting suitable pomelo cultivars for juice processing.

Physicochemical and microbiological assessment of Nypa fruticans sap collected in Sarawak, Malaysia

Nipa sap is a sweet and translucent beverage that originated from nipa palm (Nypa fruticans) tree. In Sarawak, nipa sap become raw material for nipa sugar or locally known as gula apong. However, nipa sap undergoes natural fermentation that alters the properties of nipa sap including taste, aroma and quality. Fermented nipa sap is whitish colour with an unpleasant aroma and taste, which makes it unacceptable for consumption. Hence, it is no longer suitable to make nipa sugar. This study aimed to determine the physicochemical and microbiological changes of nipa palm sap from fresh to fermented. The nipa sap was allowed to undergo natural fermentation at room temperature for 56 days. Samples were collected every 24 hrs for the first week and once a week in the subsequent week. The selected physiochemical qualities were analysed using high-performance liquid chromatography (HPLC) whereas the microbial content was analysed using spread plating. Fresh nipa sap showed the highest load of sugar (334.2±12 g/L) with sucrose as the main sugar found (231.5±4.3 g/L), followed by fructose (42.1±1.2 g/L), and glucose (29.7±3.2 g/L). Fresh nipa sap also possessed the lowest load of ethanol (0.08±0.03 g/L), lactic acid (1.09±0.06 g/L), and acetic acid (0.05±0.01 g/L) as well as microbial and yeast concentration. Later, ethanol started to accumulate on day 4 (9.80±0.1 g/L) and the highest peak was on day 21 (19.1±2.01 g/L). The microbial concentration changed as well, affecting the quality of nipa sap. As nipa sap plays such an important role in the lifestyle of people in Sarawak, this study provides a better understanding of the microbiology and biochemistry of its fermentation process. Hence, proper planning for handling fresh nipa sap should be considered to ensure the quality of value-added product production.

Polyphenol and Flavonoid Stability of Wild Blueberry (Sideroxylon mascatense) during Air- and Freeze-Drying and Storage Stability as a Function of Temperature

Būt (Sideroxylon mascatense) is an indigenous wild blueberry found in Oman. It has a very short season and is commonly preserved by drying. The aims of this study were to determine the physico-chemical characteristics and stability of phytochemicals (i.e., polyphenols and flavonoids) in the berries during drying (i.e., freeze-drying at -40 °C and air-drying at 60 and 90 °C) and the polyphenol stability of the dried berries as a function of storage temperature (i.e., 90, 70, 60, 40, 20, and -20 °C). The moisture content of fresh berry flesh was 64.5 g/100 g sample (wet basis). The crude protein and fat contents were higher in the seeds than in the flesh. Glucose and fructose were the main sugars and their concentrations were highest in the sample air-dried at 60 °C. The initial total polyphenol content (TPC) and total flavonoid content (TFC) of the flesh were 2.009 mg gallic acid equivalent (GAE)/g dry-solids and 0.199 mg catechin equivalent (CE)/g dry-solids, respectively. The samples air-dried at 90 °C and freeze-dried at -40 °C had higher TPC (i.e., 2.638 mg GAE/g dry-solids) and TFC (i.e., 0.395 mg CE/g dry-solids), respectively. There was a significant difference between the TPC and TFC of fresh and dried wild berries (p < 0.05). The freeze-dried wild berries retained a high TPC compared to the air-dried samples. The polyphenol storage stability of freeze-dried wild berries at different storage temperatures showed two phases: an initial release phase followed by a decay phase. The polyphenol storage stability was modeled using the Peleg model and the kinetic parameters were correlated with the storage temperature.

Leaf metabolomics and molecular networking of wild type and mutant genotypes of chia (Salvia hispanica L.)

Salvia hispanica L., commonly named Chia, is a food plant from Central America and Australia, producing seeds whose consumption has been increasing in the last decade. Several articles analysed the seeds metabolite content. However, few is known about Chia leaves. This work is the first report on the whole metabolite profile of chia leaves, determined by spectroscopic methods including NMR, GC-MS and LC-MS coupled with chemometrics analysis. Additionally, molecular networking has been applied to the LC-MS data to determine the flavonoid composition. Different chia sources were compared: one commercial (black) and three early flowering (G3, G8 and G17) mutant genotypes cultivated at two irrigation regimes (50 and 100%). Organic extracts were mainly composed by saturated and mono- and polyunsaturated fatty acids with palmitic being the most abundant followed by oleic and linolenic acids. Aqueous extracts contained glucose, galactose, and fructose as main sugars. Flavonoids were based on vitexin and orientin and their analogues. Chemical composition of early flowering genotypes was quite similar to commercial black chia with the exception of G8 showing significant differences in the polar phase. A generally highest content of omega-9 fatty acids has been found in the early flowering genotypes along with high content of nutraceuticals suggesting them as a potential source of raw materials for the food/feed industry.

Variations of freezing tolerance and sugar concentrations of grape buds in response to foliar application of abscisic acid.

The purpose of this study was to explore the mechanism of ABA-induced freezing tolerance increase in grapevines. The specific objectives were to evaluate the impact of ABA treatment on soluble sugar concentration in grape buds and determine the correlations between freezing tolerance and ABA-affected soluble sugar concentration. Vitis spp 'Chambourcin' and Vitis vinifera 'Cabernet franc' were treated with 400 and 600 mg/L ABA in the greenhouse and field. The freezing tolerance and soluble sugar concentration of grape buds were measured monthly during the dormant season in the field and at 2wk, 4wk, and 6wk after ABA application in the greenhouse. It was observed that fructose, glucose, and sucrose are the main soluble sugars that correlate with freezing tolerance of grape buds and the synthesis of these sugars can be enhanced by ABA treatment. This study also found that ABA application can promote raffinose accumulation, however, this sugar may play a more important role in the early acclimation stage. The preliminary results suggest that raffinose accumulated first in buds, then its decrease in mid-winter corresponded with the increase of smaller sugars, such as sucrose, fructose, and glucose, which in turn, corresponded with reaching maximum freezing tolerance. It is concluded that ABA is a cultural practice tool that can be used to enhance freezing tolerance of grapevines.

Magnesium Effects on Carbohydrate Characters in Leaves, Phloem Sap and Mesocarp in Wax Gourd (Benincasa hispida (Thunb.) Cogn.)

Magnesium (Mg) is critical for agricultural production and human health. The wax gourd yield was greatly affected by Mg fertilizer and it serves as an excellent crop to study Mg functioning in sink growth; however, as a Cucurbitaceae plant which is called a raffinose family oligosaccharides (RFOs)-transporting plant, its adaptive mechanism of photoassimilates transportation and distribution to Mg nutrients remains unknown. Herein, we used two Mg treatments (+Mg 90 kg ha−1; CK as control 0 kg ha−1) to observe the effects of Mg on the photoassimilates status in the leaves, phloem sap and fruit of wax gourd grown across the entire growth stage under a field condition. For the first time, we confirmed that stachyose and raffinose, which accounted for 54.9–78.0% of the total carbohydrates across the whole growth phase in the phloem sap, were the most predominant sugars used for the long-distance transport of wax gourds. They were strongly increased by Mg application which started from the seedling stage to the end of growing season. This response was earlier and more dramatic than the over-accumulation of sucrose in leaves regardless of positions. Hexoses (glucose plus fructose) were the main soluble sugars in the source leaves as well as in the mesocarp tissues, and their responses to Mg varied with temporal and spatial differences. The difference in the sugar status in the leaves between the upper, middle and lower positions is closely related to the concentration of Mg ions. Compared with Mg deficiency (CK), Mg application stimulated sugar accumulation in the leaves at the seedling and flowering stages by 10.6–24.5%. On the contrary, after fruit set, Mg supplementation significantly reduced the soluble sugar concentration in leaves by 33.5–67.9%. Mg treatment also spiked the fructose and glucose in fruit at the fruit expansion stage by 26.7% and 16.4%, respectively. Taken together, our results showed that Mg tailors the carbohydrate status in the source (leaves), flow (phloem sap) and sink (mesocarp tissues) in wax gourds, especially during the fruit growth period. The lower stachyose in the phloem at the beginning of fruit setting may be an early indication of a curtailed sink process in wax gourds grown in Mg deficient soil.

Valorisation of the invasive alga Rugulopteryx okamurae through the production of monomeric sugars

Rugulopteryx okamurae is an invasive brown alga causing severe environmental and economic problems on the western Mediterranean coasts. Thus, in addition to the difficulties caused to the fishing and tourism sectors, there is a need to manage its accumulation on the beaches. This work aims to valorise this waste by using it as raw material for producing monosaccharides through a two-stage sequential process. These sugars could be used for different fermentative processes to obtain high-value-added bioproducts. In this work, biological pretreatment of the previously conditioned seaweed with the fungus Aspergillus awamori in solid-state fermentation (SSF), followed by enzymatic hydrolysis with a commercial enzyme cocktail, was performed. The effect of the extension of the biological pretreatment (2, 5, 8 and 12 days) on the subsequent release of total reducing sugars (TRS) in the enzymatic hydrolysis stage was studied. To analyse this effect, experimental data of TRS produced along the hydrolysis were fitted to simple first-order kinetics. Also, the secretion of cellulase and alginate lyase by the fungus, along with the biological pretreatment, was determined. The results suggest that 5 days of biological pretreatment of the macroalgae with A. awamori followed by enzymatic saccharification for 24 h with Cellic CTec2® (112 FP units/g of dry biomass) are the best conditions tested, allowing the production of around 240 g of TRS per kg of dried biomass. The main sugars obtained were glucose (95.8 %) and mannitol (1.5 %), followed by galactose (1 %), arabinose (0.9 %) and fucose (0.5 %).Key points• Five-day SSF by A. awamori was the best condition to pretreat R. okamurae.• Five-day SSF was optimal for alginate lyase production (1.63 ±0.011 IU/g biomass).• A maximum yield of 239 mg TRS/g biomass was obtained (with 95.8 % glucose).Graphical

Bacterial cellulose production by a strain of Komagataeibacter rhaeticus isolated from residual loquat.

In this study, loquat extract was selected as a promising substrate for bacterial cellulose (BC) production. A new BC-producing bacterial strain was isolated from residual loquat and identified as Komagataeibacter rhaeticus. BC production with different carbon sources and with loquat extract was investigated. Among all tested carbon sources, glucose was demonstrated to be the best substrate for BC production by K. rhaeticus, with up to 7.89g/L dry BC obtained under the optimal initial pH (5.5) and temperature (28°C) with 10days of fermentation. The total sugar and individual sugars were investigated in different loquat extracts, in which fructose, glucose, and sucrose were the three main sugars. When loquat extract was prepared with a solid‒liquid (S-L) ratio of 2:1, the concentrations of glucose, fructose, and sucrose were 7.91g/L, 9.31g/L, and 2.84g/L, respectively. The BC production obtained from loquat extract was higher than that of other carbon sources except glucose, and 6.69g/L dry BC was obtained from loquat extract with an S-L ratio of 2:1. After BC production, all sugars substantially decreased, with the utilization of glucose, fructose, and sucrose reaching 93.9%, 87.9%, and 100%, respectively. These results suggested that the different sugars in loquat extract were all carbon sources participating in BC production by K. rhaeticus. Structural and physicochemical properties were investigated by SEM, TGA, XRD, and FT-IR spectroscopy. The results showed that the structural, chemical group, and water holding capacity of BC obtained from loquat extract were similar to those of BC obtained from glucose, but the crystallinity and thermal stability of BC were higher than those of BC from mannose and lactose but lower than those of BC from glucose and fructose. KEY POINTS: • A new BC-producing strain was isolated and identified as Komagataeibacter rhaeticus. • Loquat extract is an alternative substrate for BC production. • The BC obtained from loquat extract owns advanced physicochemical properties.

Properties of Water‐Soluble Xylan from Different Agricultural By‐Products and their Production of Xylooligosaccharides

AbstractXylooligosaccharides (XOS) are non‐digestible oligosaccharides with a significant role as functional food ingredients in the food industry. The present research is undertaken to evaluate water soluble xylan (WSX) extraction from eight different sources using water at ambient temperature (25 ± 2 °C) and structural characterization (FTIR, NMR, XRD, and TGA). Enzymatic production of XOS from extracted substrates and its characterization using HPLC‐RID and FTIR is determined. WSX from orange fleshed sweet potato peel shows highest yield (9%), while the least (2.48%) is from Teff seed coat. FTIR structural identification of xylan confirms the presence of β‐glycosidic linkages and acetyl groups; whereas 1H NMR validates the occurrence of β‐D‐1,4‐xylopyranose backbone with α‐L‐arabinofuranose and 4‐O‐methylglucuronic acid substituents. XRD and TGA characteristics of the extracts indicate similarities in the eight sources in comparison with standard beech wood xylan. WSX is hydrolyzed with endoxylanase to obtain XOS (highest yield of 57.16 ± 1.01% in Cassava cake; lowest yield of 21.72 ± 0.72% in Bambara groundnut). HPLC‐RID reveals xylobiose as the main monomeric sugar component (DP 2) and β‐linkages are identified by FTIR in all the sources. The study suggests the potential commercial production of XOS from the analyzed agricultural by‐products.

Nutritional, chemical and antioxidant evaluation of Armuña lentil (Lens culinaris spp): Influence of season and soil

Lentils (Lens culinaris spp.) are a type of edible pulse consumed and produced worldwide; they are known for their valuable nutritional assets. The nutritional and chemical profiles of 34 Armuña lentil samples were assessed together with their antioxidant capacity. In addition, the influence of both the climatic conditions during the growing season and the soil type in which they grow (Luvisol and Cambisol) on nutritional and chemical profiles was also evaluated. Our results showed large amounts of valuable nutrients, such as carbohydrates, of which approximately 47.06 % and 29.11 % consist of fibers and starch respectively and significant amounts of proteins (20.47 to 25.56 g/100 g fw) and ashes. Sucrose stood out as the main free sugar in this variety, and oxalic and γ-tocopherol as the main organic acid and tocopherol isoform respectively. Fatty acid assessment showed the prevalence of PUFAs (45.3 to 63.7 %). A high antioxidant capacity (TBARS and OxHLIA) was also observed. Our results indicate that the growing season has a significant impact on the major nutrients in lentils such as the concentration of fat, ashes, fibers, and fructose and to a lesser extent proteins and sucrose. In addition, the two different soil types in this study do not seem to affect any of the parameters analyzed.

Molecular structures of high- and low-methoxy water-soluble polysaccharides derived from peas and their functions for stabilizing milk proteins under acidic conditions

The structural and functional properties of two different pea water-soluble polysaccharides, a high methyl-esterified (HM-SPPS; degree of methyl esterification (DMe): 71.0 %) and low methyl-esterified SPPS (LM-SPPS; DMe: 25.2 %) were investigated. The two extracts did not vary in composition and showed a weight average molecular mass of about 1,000 kDa, as measured by size exclusion chromatography equipped with a multi-angle light scattering detector. Both HM-SPPS and LM-SPPS had similar sugar compositions, with arabinose 42.2–47.1 %, glucose 26.6–31.0 %, and galacturonic acid 17.5–18.0 %, as their main sugars. Their charge varied as a function of pH. The molecular structure was observed by a scanning probe microscope and showed a straight chain structure with small branches. The structure was similar to that already reported for polysaccharides from kidney bean. SPPS molecules interact with acidified milk protein particles at pH < 4.4. There were differences between the two SPPS. LM-SPPS could stabilize a model acidified milk dispersion with minimal aggregation between pH 3.6–4.4, while HM-SPPS showed the presence of bridging flocculation caused by polysaccharide’s entanglements. It was concluded that SPPS stabilizes acidified protein by steric and electrostatic repulsion

Effect of foliar applications on the qualitative and quantitative characters of cv. Assyrtiko and cv. Mavrotragano in the island of Santorini, under vineyard conditions

The Mediterranean basin is regarded as one of the world’s most affected regions by climate changes. Traditionally, viticulture in this region has been coping with high temperatures, heat waves and drought. Such particularly extreme conditions, which induce severe abiotic stress on plants, are expected to intensify due to the predicted climate changes in the future. Santorini Island seems not to be an exception. The increase of temperature and solar radiation, in combination with the low availability of water, made necessary the development and the application of methods in order to cope with the abiotic stresses of the grapevine. This study examined the foliar applications and their effect on the qualitative and quantitative characteristics of the grapes by spraying application of the two indigenous varieties of the vineyard of Santorini (Greece), Assyrtiko, and Mavrotragano. The experiment took place in the cultivation season 2019-2020. Specifically, treatments with kaolin and calcium carbonate, two inert materials capable of reflecting radiation were evaluated. In the case of Assyrtiko, the effect of kaolin and calcium carbonate was examined on two different training systems, on the traditional training system of Santorini ‘kouloura’, and on a single Guyot training system. In the case of Mavrotragano, the effect of kaolin and calcium carbonate was examined on the vines which are trained in double Guyot training system. Mechanical analyses of the grapes and berries were performed, as well as measurements of the characters of the must during the stage of technological maturity. The content of the phenolic compounds was determined in the skins and seeds and the antioxidant capacity of the samples was measured by using different methods, FRAP and DPPH, by the use of spectrophotometry. At the same time, the analysis of High-Pressure Liquid Chromatography (HPLC) indicated the concentrations of the main individual sugars and acids in the must as well as the measurements of the skin individual anthocyanins for cv Mavrotragano. The results of the treatments showed that the analyses related to weight, length, and width of the grapes and berries and the measurements of pH and total titratable acidity for both training systems and both varieties did not seem to be affected. Also, compared to grapes from control treatments, the levels of most phenolic compounds and anthocyanins of the sprayed samples mostly increased, and as a result, this leads to grapes of better quality, thus better wine quality, since most measurements conducted in the current experiment are also directly correlated with the organoleptic properties of the wine. Therefore, the use of kaolin and calcium carbonate through foliar applications constitutes an important means of adaptation of the vines which are grown under conditions of drought, in terms of economic and environmental sustainability reasons, while improving the quality of grapes.

The Main Physicochemical Characteristics and Nutrient Composition during Fruit Ripening of Stauntonia obovatifoliola Subsp. Urophylla (Lardizabalaceae)

Stauntonia obovatifoliola Hayata subsp. urophylla is a novel edible and healthy fruit in China, commonly known as “Jiuyuehuang” (September yellow). The fully ripe fruit of S. obovatifoliola subsp. urophylla has a soft fruit pulp texture, golden flesh, and sweet flavor which is very popular with the locals. In this paper, we have investigated the fruit appearance quality, physiochemical quality, and nutritional quality of S. obovatifoliola subsp. urophylla that was harvested at six stages (S1: 60 DAFB, S2: 90 DAFB, S3: 130 DAFB, S4: 160 DAFB, S5: 190 DAFB, S6: 205 DAFB). An increase in fruit size (including single fruit weight, fruit length, and fruit diameter) was related to the ripeness stage of fruit development. The total soluble solids, firmness, dry matter, sugar and starch showed remarkable changes as the fruit approached ripening (S5–S6 stage). The main sugar components in the fruit were fructose, glucose, and maltose. The contents of fructose, glucose, and total sugars in S. obovatifoliola subsp. urophylla fruit progressively increased from the S1 to the S6 stage while increasing sharply from the S4 to the S5 stage. As for the content of maltose and starch, they both showed an increasing trend from the S1 to the S4 stage but decreased sharply at the S5 stage. The vitamin B, vitamin C, total phenolics, total flavonoids, and amino acid levels showed an overall downward trend during fruit development. To our knowledge, this is the first study to compare the phytochemical characteristics, nutrient composition, and antioxidant content during the different fruit development stages. The results of this study may provide a scientific basis for clarifying the growth and development characteristics of S. obovatifoliola subsp. urophylla fruit and the further utilization of these excellent medicinal and edible germplasm resources.