Changes in non-structural carbohydrate composition during bulbing in sweet and high-solid onions in field experiments

Study of the effects of pasteurization and selected microbial starters on functional traits of fermented table olives

Table olives are one of the most known fruit consumed as fermented food, being a fundamental component of the Mediterranean diet. Their production and consumption continue to increase globally and represent an important economic source for the producing countries. One of the most stimulating challenges for the future is the modernization of olive fermentation process. Besides the demand for more reproducible and safer production methods that could be able to reduce product losses and potential risks, producers and consumers are increasingly attracted by the final product characteristics and properties on human health. In this study, the contribution of microbial starters to table olives was fully described in terms of specific enzymatic and microbiological profiles, nutrient components, fermentation-derived compounds, and content of bioactive compounds. The use of microbial starters from different sources was tested considering their technological features and potential ability to improve the functional traits of fermented black table olives. For each fermentation assay, the effects of controlled temperature (kept at 20 °C constantly) versus not controlled environmental conditions (oscillating between 7 and 17 °C), as well as the consequences of the pasteurization treatment were tested on the final products. Starter-driven fermentation strategies seemed to increase both total phenolic content and total antioxidant activity. Herein, among all the tested microbial starters, we provide data indicating that two bacterial strains (Leuconostoc mesenteroides KT 5-1 and Lactiplantibacillus plantarum BC T3-35), and two yeast strains (Saccharomyces cerevisiae 10A and Debaryomyces hansenii A15-44) were the better ones related to enzyme activities, total phenolic content and antioxidant activity. We also demonstrated that the fermentation of black table olives under not controlled environmental temperature conditions was more promising than the controlled level of 20 °C constantly in terms of technological and functional properties considered in this study. Moreover, we confirmed that the pasteurization process had a role in enhancing the levels of antioxidant compounds.

An ethnopharmacological, phytochemical, and pharmacological overview of onion (Allium cepa L.)

ETHNOPHARMACOLOGICAL RELEVANCE

Onion (Allium cepa L.) is one of the most widely distributed species within the Allium genus of family Amaryllidaceae. Onion has been esteemed for its medicinal properties since antiquity. It has been consumed for centuries in various indigenous cultures for the management of several ailments including microbial infections, respiratory, gastrointestinal, skin and cardio-vascular disorders, diabetes, renal colic, rheumatism, sexual impotence, menstrual pain, and headache. However, so far, there is a scarcity of recent data that compiles the plant chemistry, traditional practices, biological features, and toxicity.

AIM OF THE WORK

The aim of this review is to provide a comprehensive and analytical overview of ethnopharmacological uses, phytochemistry, pharmacology, industrial applications, quality control, and toxicology of onion, to offer new perspectives and broad scopes for future studies.

MATERIALS AND METHODS

The information gathered in this review was obtained from various sources including books, scientific databases such as Science Direct, Wiley, PubMed, Google Scholar, and other domestic and foreign literature.

RESULTS

Onion has a long history of use as a traditional medicine for management of various conditions including infectious, inflammatory, respiratory, cardiovascular diseases, diabetes, and erectile dysfunction. More than 400 compounds have been identified in onion including flavonoids, phenolic acids, amino acids, peptides, saponins and fatty acids. The plant extracts and compounds showed various pharmacological activities such as antimicrobial, antidiabetic, anti-inflammatory, anti-hyperlipidemic, anticancer, aphrodisiac, cardioprotective, and neuroprotective activities. In addition to its predominant medicinal uses, onion has found various applications in the functional food industry.

CONCLUSION

Extensive literature analysis reveals that onion extracts and bioactive constituents possess diverse pharmacological activities that can be beneficial for treating various diseases. However, the current research primarily revolves around the documentation of ethnic pharmacology and predominantly consists of in vitro studies, with relatively limited in vivo and clinical studies. Consequently, it is imperative for future investigations to prioritize and expand the scope of in vivo and clinical research. Additionally, it is strongly recommended to direct further research efforts towards toxicity studies and quality control of the plant. These studies will help bridge the current knowledge gaps and establish a solid basis for exploring the plant's potential uses in a clinical setting.

The longitudinal association between onion consumption and risk of depressive symptoms: results from the TCLSIH Cohort study and the UK Biobank

Background and aims: Onions have shown antidepressant effects but relevant evidence from people was limited. Thus, we aimed to explore the prospective association between onion consumption and risk of depressive symptoms in the general population. Methods: We used data from 2 cohorts: the Tianjin Chronic Low-grade Systemic Inflammation and Health (TCLSIH) cohort included 7739 participants (males, 57.6%) with a mean age of 39.5 years, and the UK Biobank included 169 806 individuals (males, 45.2%) with a mean age of 55.7 years. In the TCLSIH cohort, onion consumption was assessed by a validated food frequency questionnaire from May 2013; depressive symptoms were evaluated by the Chinese version of the Self-Rating Depression Scale (SDS scores ≥ 45) and were assessed up to 2018. In the UK Biobank, onion consumption was measured by 1-5 times validated 24-hour dietary recalls in 2006-2010; depressive symptoms were determined through the linked hospital records and death registries and were assessed up to 2018. Multivariable Cox proportional hazards models were employed to determine the association between onion consumption and risk of depressive symptoms. Results: A total of 1098 and 1924 cases of depressive symptoms were identified during 15 004 person-years and 1 243 832 person-years of follow-up in the TCLSIH cohort and the UK Biobank, respectively. After adjusting for many confounding factors, the fully adjusted HRs (95% CI) of depressive symptoms comparing the higher levels to the lowest level of onion consumption were 0.78 (0.65, 0.94), 0.73 (0.61, 0.87), and 0.77 (0.64, 0.92) in the TCLSIH cohort (p for trend = 0.01); and were 0.79 (0.68, 0.93), 0.81 (0.69, 0.94), and 0.97 (0.85, 1.12) in the UK Biobank (p for trend = 0.07). Similar associations were observed in the sensitivity analyses. Conclusion: Our results indicated that habitual onion consumption was associated with a lower risk of depressive symptoms in two cohorts. However, this association was not statistically significant in the highest level of onion consumption in the UK Biobank.

Allium cepa: A Treasure of Bioactive Phytochemicals with Prospective Health Benefits

As Allium cepa is one of the most important condiment plants grown and consumed all over the world, various therapeutic and pharmacological effects of A. cepa were reviewed. Onion (Allium cepa) is a high dietary fiber-rich perennial herb that is placed under the family Amaryllidaceae. It contains high concentration of folic acid, vitamin B6, magnesium, calcium, potassium, and phosphorus as well as vitamins and minerals. It is widely used as an antimicrobial agent, but it showed anticancer, antidiabetic, antioxidant, antiplatelet, antihypertensive, and antidepressant effects and neuroprotective, anti-inflammatory, and antiparasitic effects and so on. It is said to have beneficial effects on the digestive, circulatory, and respiratory systems, as well as on the immune system. This review article was devoted to discussing many health benefits and traditional uses of onions in pharmacological perspectives, as well as the safety/toxicological profile. If more detailed research on this perennial herb is conducted, it will open the door to an infinite number of possibilities.

Suitability of stationary phase for LC analysis of biomolecules

Biologically active compounds such as carotenoids/isoprenoids, vitamins, steroids, saponins, sugars, long chain fatty acids, and amino acids play a very important role in coordinating functions in living organisms. Determination of those substances is indispensable in advanced biological sciences. Engineered stationary phase in LC for the analysis of biomolecules has become easier with the development of chromatographic science. In general, C₁₈ column is being used for routine analysis but specific columns are being used for specific molecule. Monolithic columns are found to have higher efficiency than normal column. Among recent introduction, triacontyl stationary phases, designed for the separation of carotenoid isomers, are widely used for the estimation of carotenoids. In comparison to conventional C₁₈ phases, C₃₀ phases exhibited superior shape selectivity for the separation of isomers of carotenoids. It is also found useful for better elution and analysis of tocopherols, vitamin K, sterols, and fatty acids. Vitamin K, E, and their isomers are also successfully resoluted and analyzed by using C₃₀ column. Amino bonded phase column is specifically used for better elution of sugars, whereas phenyl columns are suitable for the separation and analysis of curcuminoids and taxol. Like triacontyl stationary phase, pentafluorophenyl columns are also used for the separation and analysis of carotenoids. Similarly, HILIC column are best suited for sugar analysis. All the stationary phases are made possible to resolute and analyze the target biomolecules better, which are the future of liquid chromatography. The present article focuses on the differential interaction between stationary phase and target biomolecules. The applicability of these stationary phases are reported in different matrices.

Impact of Cultivation Method and Cultivar Selection on Soluble Carbohydrates and Pungent Principles in Onions ( Allium cepa L.)

The composition of soluble carbohydrates such as fructooligosaccharides (FOS) in onions ( Allium cepa L.) plays a role regarding their digestibility, long-term storability, and processability. Qualitative and quantitative profiles of soluble carbohydrates were determined in 23 different onion samples comprising 20 cultivars grown at two different locations in 2014 and 2015. FOS concentrations were 1.1-fold higher in set grown onions than in seed grown onions ( p = 0.001). FOS levels of dehydrator cultivars were higher (overall average: 130.8 ± 42.4 g/L FOS) than those of common set and seed (61.8 ± 20.0 and 29.4 ± 14.7 g/L FOS) grown cultivars. Consequently, cultivation method (seed vs. set planting) and cultivar selection were crucial when aiming at onions with defined FOS contents. Besides FOS and other carbohydrate-related parameters, levels of alk(en)yl cysteine sulfoxides, indicating onion oil yield and pungency of onions, were determined to be different in dehydrator onions (13.1 ± 2.6 μmol/mL), seed (8.4 ± 1.3 μmol/mL), and set grown onions (7.5 ± 1.6 μmol/mL).

Change in carbohydrate and enzymes from harvest to sprouting in garlic

Changes in carbohydrates, enzymes, and pigments were investigated in the Red Garlic (Allium sativum L.) cv. Azarshahr bulbs in storage from harvest to sprouting. For storage period, garlic cloves of the same diameter with 3-4 g weight were arranged in dark condition and exposed to 4 and 21°C, separately. Soluble sugar, total sugar, glucose, sucrose, fructose, starch, chlorophyll a, b, ab, carotenoid, anthocyanin, lipase, α-amylase, and protease were measured every 2 weeks up to sprouting time. Result revealed that starch, lipase, and protease levels declined at the end of storage when clove sprouting started at both 4 and 21°C storage temperature. Starch, glucose, chlorophyll a, b, ab, and carotenoid content during the first 14 days and sucrose at 42 days showed a decreasing trend. Anthocyanin showed an increasing trend 14 and 42 days after harvesting and then decreased at the end of storage (when sprouting began) at both 4 and 21°C storage periods. Finally, starch, glucose, and sucrose measurement can be used as a criterion to predict sprouting time of garlic, due to the decrease in the levels of starch, lipase, and protease, and increase in the levels of α-amylase, glucose, and sucrose in garlic cloves under storage.

Effect of different storage temperature on chemical composition of onion (Allium cepa L.) and its enzymes

Onion stored at 4, 10, and 25 °C for 9 months were analyzed for changes in quercetin and its glucosidase content, enzymes, pyruvic acid, and sugar content. During storage, concentration of quercetin and its glucosidase showed an irregular variation at all studied temperature but at 4 °C the rate was high as compared to 10 and 25 °C. The enzymatic activity of Q4'G glucosidase and Q4'glucosyltransferase increased progressively until six months at 4, 10 and 25 °C, but later it started to decrease. At 4 and 10 °C, peroxidase activity increased during the first five weeks then decreased, while at 25 °C peroxidase activity decreased progressively after two months storage. Fructose, glucose and sucrose showed a different although more regular pattern by decreasing progressively at 4, 10 °C. At 4 °C fructose and glucose accumulated in the initial 3 to 4 months of storage while sucrose was unchanged. However, at 10 and 25 °C, fructose and glucose concentration continuously decreased, while sucrose increased consistently. Onion pyruvic acid increased at 4 and 10 °C during the first six months, while at 25 °C the fluctuation was observed during the whole storage period. Overall, we conclude that storage at 4 °C maintained the quality of onions best, as evidenced by the positive changes.

Temperature-dependent studies on the total phenolics, flavonoids, antioxidant activities, and sugar content in six onion varieties

Heating effect on total phenol, flavonoids, antioxidant activity, and sugar content of six onion varieties has been quantitatively investigated to explore the effect of different temperatures. The onion varieties comprised one red-skinned variety, two white-skinned varieties, and three yellow-skinned varieties. The heating temperature was scanned at 80°C, 100°C, 120°C, and 150°C for 30 minutes each, and quantitative analysis was performed relative to the powdered onion at ambient temperature. Quercetin, glucosides and sugar content were analyzed using high-performance liquid chromatography. The total phenolic and antioxidant content increased in all six varieties. The total flavonoid levels showed a considerable change. On heating the onion samples at 120°C for 30 minutes, the red-skinned variety showed the highest level of total phenolic content [13712.67 ± 1034.85 μg of gallic acid equivalent/g dry weight (μg GAE/g DW)] and total flavonoids [3456.00 ± 185.82 μg of quercetin equivalents/g dry weight (μg Q/g DW)], whereas the content of total phenolics and total flavonoids were 13611.83 ± 341.61 μg GAE/g DW and 3482.87 ± 117.17 μg Q/g DW, respectively, for the yellow-skinned (Sunpower) variety. Quercetin and its glucoside contents increased up to 120°C and then decreased at 150°C, whereas the sugar content continuously decreased with heating. All cultivars showed the same pattern in the heating effect, and the predominant flavonoids were destroyed at higher temperatures. Therefore, it is improper to expose onion powder to a temperature higher than 120°C.

Quantitative metabolite profiling of edible onion species by NMR and HPLC-MS

Allium genus is a treasure trove of valuable bioactive compounds with potentially therapeutically important properties. This work utilises HPLC-MS and a constrained total-line-shape (CTLS) approach applied to (1)H NMR spectra to quantify metabolites present in onion species to reveal important inter-species differences. Extensive differences were detected between the sugar concentrations in onion species. Yellow onion contained the highest and red onion the lowest amounts of amino acids. The main flavonol-glucosides were quercetin 3,4'-diglucoside and quercetin 4'-glucoside. In general, the levels of flavonols were, higher in yellow onions than in red onions, and garlic and leek contained a lower amount of flavonols than the other Allium species. Our results highlight how (1)H NMR together with HPLC-MS can be useful in the quantification and the identification of the most abundant metabolites, representing an efficient means to pinpoint important functional food ingredients from Allium species.

Measurement of the distribution of non-structural carbohydrate composition in onion populations by a high-throughput microplate enzymatic assay

BACKGROUND

Non-structural carbohydrate (NSC; glucose, fructose, sucrose and fructan) composition of onions (Allium cepa L.) varies widely and is a key determinant of market usage. To analyse the physiology and genetics of onion carbohydrate metabolism and to enable selective breeding, an inexpensive, reliable and practicable sugar assay is required to phenotype large numbers of samples.

RESULTS

A rapid, reliable and cost-effective microplate-based assay was developed for NSC analysis in onions and used to characterise variation in tissue hexose, sucrose and fructan content in open-pollinated breeding populations and in mapping populations developed from a wide onion cross. Sucrose measured in microplates employing maltase as a hydrolytic enzyme was in agreement with HPLC-PAD results. The method revealed significant variation in bulb fructan content within open-pollinated 'Pukekohe Longkeeper' breeding populations over a threefold range. Very wide segregation from 80 to 600 g kg(-1) in fructan content was observed in bulbs of F2 genetic mapping populations from the wide onion cross 'Nasik Red × CUDH2150'.

CONCLUSION

The microplate enzymatic assay is a reliable and practicable method for onion sugar analysis for genetics, breeding and food technology. Open-pollinated onion populations may harbour extensive within-population variability in carbohydrate content, which may be quantified and exploited using this method. The phenotypic data obtained from genetic mapping populations show that the method is well suited to detailed genetic and physiological analysis.

Solutions are solutions, and gels are almost solutions

Molecular gastronomy is the scientific discipline that looks for mechanisms of phenomena occurring during dish preparation and consumption. Solutions are studied because most foods, being based on animal and plant tissues, are gels, with a liquid fraction and a continuous solid phase. This is why food can be studied in situ using liquid NMR spectroscopy in the frequency domain (isq NMR). Using such tools, processes of the kind F@M → F' @ M' (where F stands for the food matrix, M for its environment, and @ for inclusion) were investigated for various processes as classified using the complex disperse system/non-periodical organization of space formalism (“disperse systems formalism”, DSF). As an application of these studies, “note by note cuisine” was promoted as a new paradigm for culinary activities.

Effect of extraction procedure on measured sugar concentrations in onion (Allium cepa L.) bulbs

Bulb samples from a range of onion cultivars grown over three consecutive years were freeze-dried and the resulting powders extracted using three previously reported methods. The extracts were analyzed for fructose, glucose, and sucrose content using HPLC coupled with ELSD, and for fructans using MALDI-MS. The three methods gave differing results, indicating that the extraction procedure is crucial in the determination of the concentration and ratios of nonstructural carbohydrates in onion bulbs. O'Donoghue et al.'s method (O'Donoghue, E. M.; Somerfield, S. D.; Shaw, M.; Bendall, M.; Hedderly, D.; Eason, J.; Sims, I. J. Agric. Food Chem. 2004, 52, 5383-5390), which utilized a more polar solvent (62.5% (v/v) aqueous methanol) and also had the benefit of shorter extraction times and lower temperatures, was far superior to 80% (v/v) ethanol-based methods in extracting significantly greater amounts of fructose, glucose, and sucrose from all onion bulbs tested. Discrepancies between and within cultivars tested also demonstrated that the ratio of monosaccharides to sucrose was affected by extraction method, such that some caution should be given to interpreting some previous work on elucidating the nonstructural carbohydrate composition in onion.

Chemoprevention of aberrant crypt foci in the colon of rats by dietary onion

Onion intake might reduce the risk of colorectal cancer, according to epidemiology. However, Femia showed in 2003 that diets with a 20% onion intake increase carcinogenesis in rats. We speculated this dose was too high. Prevention of initiation was thus tested in 60 rats given a 5% dried onion diet or AIN76 diet, and initiated 12 days later with azoxymethane (AOM, 1x20 mg/kg i.p.), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ, 2x200 mg/kg p.o.), or N-nitroso-N-methylurea (2x50 mg/kg p.o.). Prevention of promotion was tested in 38 rats given AOM, then randomised to: AIN76 diet; 5% onion diet; phytochemicals diet (supplemented with propyl-disulfide, quercetine-glycosides and oligofructose); 1% pluronic F68 diet (a potent chemopreventive PEG-like block-polymer, used as a positive control). Aberrant crypt foci (ACF) were scored 30 days (initiation) or 100 days (promotion) after carcinogen injection. The onion diet given during initiation reduced the number of AOM-induced ACF (60 versus 86, p=0.03), and the size of IQ-induced ACF (1.33 versus 1.97, p=0.02). Given post-initiation, the onion diet reduced the number of ACF (34 versus 59, p=0.008) and of large ACF (6 versus 15, p=0.02). Phytochemicals diet and pluronic diet reduced ACF growth similarly. Data show that a 5% onion diet reduced carcinogenesis during initiation and promotion stages, and suggest this chemoprevention is due to known phytochemicals.

Genetic mapping of a major gene affecting onion bulb fructan content

The non-structural dry matter content of onion bulbs consists principally of fructose, glucose, sucrose and fructans. The objective of this study was to understand the genetic basis for the wide variation observed in the relative amounts of these carbohydrates. Bulb carbohydrate composition was evaluated in progeny from crosses between high dry matter storage onion varieties and sweet, low dry matter varieties. When samples were analysed on a dry weight basis, reducing sugar and fructan content exhibited high negative correlations and bimodal segregation suggestive of the action of a major gene. A polymorphic SSR marker, ACM235, was identified which exhibited strong disequilibrium with bulb fructan content in F(2:3) families from the 'W202A' x 'Texas Grano 438' mapping population evaluated in two environments. This marker was mapped to chromosome 8 in the interspecific population 'Allium cepa x A. roylei'. Mapping in the 'Colossal Grano PVP' x 'Early Longkeeper P12' F2 population showed that a dominant major gene conditioning high-fructan content lay in the same genomic region. QTL analysis of total bulb fructan content in the intraspecific mapping population 'BYG15-23' x 'AC43' using a complete molecular marker map revealed only one significant QTL in the same chromosomal region. This locus, provisionally named Frc, may account for the major phenotypic differences in bulb carbohydrate content between storage and sweet onion varieties.

Evaluation of carbohydrates in Pukekohe Longkeeper and Grano cultivars of Allium cepa

The storage, soluble, and structural carbohydrates of two onion cultivars, the hard, pungent Pukekohe Longkeeper (PLK) and the softer, milder Houston Grano, were analyzed to determine differences that might be related to their response to sulfur nutrition received during growth as well as their postharvest attributes and end-use suitability. PLK tissue contained 1.37 times more dry matter than Grano and was composed of more fructan and sucrose and less glucose and fructose than Grano [corrected] There were also differences in neutral sugar content, especially galactose, and the amount, size, and content of pectin fractions soluble in chelator and weak alkali. These two onion cultivars differed in their capacity to take up sulfur, but there was no statistical association between sulfur supply and any measured dry matter component.

QTL affecting soluble carbohydrate concentrations in stored onion bulbs and their association with flavor and health-enhancing attributes

Onion bulbs accumulate fructans, a type of soluble carbohydrate associated with lower rates of colorectal cancers. Higher fructan concentrations in bulbs are correlated with higher pungency, longer dormancy, and greater onion-induced antiplatelet activity (OIAA). We analyzed replicated field trials of a segregating family for types and concentrations of soluble carbohydrates in onion bulbs 90 days after harvest. Means were adjusted using dry weight as the covariant to reveal highly significant (P < 0.001) differences among parents and families for glucose, fructose, sucrose, and the fructans 1-kestose, neokestose, and (6G,1)-nystose. Fructan concentrations showed significant (P < 0.05) phenotypic correlations with each other and with sucrose, pungency, and OIAA. These observations are consistent with the hypothesis that onion bulbs accumulating fructans take up or retain less water, concentrating both soluble carbohydrates and thiosulfinates responsible for pungency and OIAA. Interval mapping of family means from the covariant analyses revealed regions on linkage groups A and D significantly (LOD > 2.68) affecting soluble carbohydrate concentrations. The enzyme catalyzing the first step of fructan polymerization, 1-sucrose-sucrose fructosyltransferase (1-SST), mapped independently of these genomic regions. One region on linkage group D near an acid-invertase gene was significantly (LOD = 3.45) associated with sucrose concentrations. This study reveals that the accumulation of sucrose in stored onion bulbs may allow for the combination of sweeter flavor with significant OIAA.Key words: quantitative trait locus, fructans, thiosulfinates, reducing sugars.

Patterns of fructan synthesized by onion fructan : fructan 6G-fructosyltransferase expressed in tobacco BY2 cells - is fructan : fructan 1-fructosyltransferase needed in onion?

•  Fructan : fructan 6G-fructosyltransferase (6G-FFT) has been proposed to be the enzyme essential for the production of neo-series inulin. Transfer of a fructose unit from short chain inulins to the C6 of the glucose residue of sucrose or inulin was proposed to be its most important characteristic. Here, we investigate the activity of 6G-FFT from onion (Allium cepa) more thoroughly. •  Tobacco BY2 suspension cultures were employed as an expression system for the fructosyltransferase 6G-FFT. Activity was measured using 1-kestose as a substrate and products were detected using high-performance anion exchange chromatography (HPAEC). •  6G-FFT showed multiple activities. An array of fructans of the inulin series and inulin neo-series were produced. First 1,1-kestotetraose and 1 and 6G-kestotetraose were synthesized, as well as 6G-kestotriose. Prolonged incubation produces a complex fructan series with a higher degree of polymerization. •  The fructan pattern observed after incubation of onion 6G-FFT with 1-kestose closely resembles the complex fructan pattern found in onion. These results questions the need for a separate fructan : fructan 1-fructosyltransferase (1-FFT) activity in onion.