Re: Sugar Pear N Major Xxx Part 1
Wesley Dupler
As with any fruit, the best way to eat a pear is to eat the whole thing. The skin is where most of the nutrients are, particularly the fiber and antioxidants. That said, be sure to wash it thoroughly before you eat it.
Sugar, organic acid, triterpenoid and phenolic composition as well as antioxidant capacity of different anatomical parts of pear were studied. Fruits and leaves of 'Radana' pear (Pyrus communis L.) were used. The results showed great quantitative differences in the composition of the pear pulp, peel, leaves and seeds. Fructose was the major sugar in pulp, seeds and peel (227.46, 45.36 and 67.49 g/kg dry mass [DM], respectively), while sorbitol was predominant in leaves (40.66 g/kg DM). Malic acid was the major organic acid, followed by citric and shikimic acids. The highest concentration of triterpenoids (3460.5 μg/g DM) was determined in pear peel, and ursolic acid was predominant. Leaves were characterized by the highest amount of phenolics (5326.7 mg/100 g DM) and the highest DPPH and FRAP values (2027.9 and 3539.6 μmol TE/100 g DM, respectively). Pear leaves and seeds may be selected as potential sources of phytochemicals.
Endothelial damage is recognized as the initial step that precedes several cardiovascular diseases (CVD), such as atherosclerosis, hypertension, and coronary artery disease. It has been demonstrated that the best treatment for CVD is prevention, and, in the frame of a healthy lifestyle, the consumption of vegetables, rich in bioactive molecules, appears effective at reducing the risk of CVD. In this context, the large amount of agri-food industry waste, considered a global problem due to its environmental and economic impact, represents an unexplored source of bioactive compounds. This review provides a summary regarding the possible exploitation of waste or by-products derived by the processing of three traditional Italian crops-apple, pear, and sugar beet-as a source of bioactive molecules to protect endothelial function. Particular attention has been given to the bioactive chemical profile of these pomaces and their efficacy in various pathological conditions related to endothelial dysfunction. The waste matrices of apple, pear, and sugar beet crops can represent promising starting material for producing "upcycled" products with functional applications, such as the prevention of endothelial dysfunction linked to cardiovascular diseases.
Understanding mechanisms of sugar accumulation and composition is essential to determining fruit quality and maintaining a desirable balance of sugars in plant storage organs. The major sugars in mature Rosaceae fruits are sucrose, fructose, glucose, and sorbitol. Among these, sucrose and fructose have high sweetness, whereas glucose and sorbitol have low sweetness. Japanese pear has extensive variation in individual sugar contents in mature fruit. Increasing total sugar content and that of individual high-sweetness sugars is a major target of breeding programs. The objective of this study was to identify quantitative trait loci (QTLs) associated with fruit traits including individual sugar accumulation, to infer the candidate genes underlying the QTLs, and to assess the potential of genomic selection for breeding pear fruit traits.
In a study of various Rosaceae species, pear had a large variation in individual sugar contents in mature fruit [24], whereas cultivar collections of apple and peach had less variation [15, 25,26,27]. Fructose is dominant in the fruit of most apple cultivars [25, 26], while sucrose is dominant in most peach cultivars [15, 27]. QTLs associated with the conversion of sucrose to hexose in mature fruit were identified on chromosomes 1 and 7 in Japanese pear [9]. Simple sequence repeats (SSRs) corresponding to the regions flanking acid invertase genes PPAIV3 and PPAIV1 were detected within the QTL intervals. The enzymes encoded by these genes are located in the vacuole, where they catalyze the conversion of sucrose to hexose. Large-effect QTLs that control the conversion of sucrose to hexose were also identified at the similar position on apple chromosome 1 [28]. Moreover, QTLs for soluble solids concentration (SSC) have been mapped on pear chromosomes 2, 4, 5, 6, and 8 [11, 29], though the effects of these QTLs fluctuated from year to year.
In this study, we collected phenotypic data for fruit traits and conducted GWAS and GS in Japanese pear. Several important QTLs for fruit traits were identified, and genes associated with sugar accumulation were predicted by GWAS using a large number of individuals. The SNP located closest to PPAIV3 on chromosome 7 and a newly identified SNP at chromosome 11 had large effects on individual sugar contents. The SNP on chromosome 4 that was associated with FRU would be useful for increasing the contents of FRU and TSC without decreasing the contents of other individual sugars. The candidate genes of QTLs identified in this study are conserved in the genomes of several Pyrinae species. Further studies including expression analysis of those genes and developing gene-specific markers would contribute to clarifying the mechanisms of sugar accumulation and validating the candidate genes for fruit traits. Fruit traits are complex and controlled by multiple factors, so it is important to accumulate relevant genetic information. The traits evaluated in this study covered the principal fruit traits in pear breeding programs, so the results obtained illustrate the feasibility of GS for fruit traits in pear.
In 2012, US per-capita consumption of fresh pears was 2.8 lb, according to the US Department of Agriculture National Agricultural Statistics Service. Per-capita consumption of all pear products was about 7 lb in 2010. About 60% of the US pear crop is sold as fresh, and 40% is processed, primarily in the form of canned product. The United States is a net exporter of pears. The largest market for fresh pears is Mexico, followed by Canada, Brazil, and Russia.
Pears are particularly rich in fructose and sorbitol, as compared with other fruits. Although most fruits contain sucrose, pears and apples contain 70% fructose, although this information is not available in standardized nutrient databases.1 Pears contain 4.5% fructose, 4.2% glucose, 2.5% sucrose, and 2.5% sorbitol.7 Comparisons of apples and pears find that pears are higher in fructose and sorbitol, whereas apples are higher in glucose and sucrose.8
Russell et al11 described the phenolic acid content of fruits consumed and produced in Scotland. Locally produced fruits had higher content of phenolic acids. The majority of the phenolic acids were conjugated to other plant components, suggesting that any health benefits derived from these compounds are likely to be after they are released or metabolized by the colonic microbiota. Pears were exceptional in that they were the only fruit that were particularly rich in methylated phenolic acids, with 70% of the phenolic acids being dimethylated (syringic and sinapic acid) compared with less than 23% for all of the other fruits analyzed.
Although it is often assumed that fruits are high in pectin and other soluble fiber, few studies have examined the specific fibers in fruits. Pears contain 71% insoluble fiber and 29% soluble fiber.1 Lignins are the noncarbohydrate part of dietary fiber and are generally linked to wheat bran and cereal fibers. Lignins in plants are biotransformed into lignans, which are phytoestrogens, by the bacteria in the gut. This type of dietary fiber also functions as an antioxidant and has been reported to be contained in pears.12
For epidemiologic studies that use food frequency measures, pears are generally captured as total fruit, either fresh or canned. Pears and apples are often listed together on food frequency instruments because they are botanically related and provide similar nutrient profiles. Larsson et al24 examined total and specific fruit and vegetable consumption and risk of stroke in a Swedish cohort. They prospectively followed 74 961 participants who had completed a food frequency questionnaire in the autumn of 1997 and were free from stroke, coronary heart disease, and cancer at baseline. Diagnosis of stroke in the cohort during follow-up was ascertained from the Swedish Hospital Discharge Registry. A total of 4089 stroke cases were found during 10.2 years of follow-up. Among individual fruit and vegetable subgroups, inverse associations with total stroke was observed for apples/pears and green leafy vegetables. The study found an inverse association of fruit and vegetable consumption with stroke risk. Particularly consumption of apples and pears and green leafy vegetables was inversely associated with stroke.
Other epidemiological studies measured the relationship between intake of major flavonoid subclasses and risk of disease. Wedick et al26 evaluated whether dietary intakes of major flavonoid subclasses were associated with risk of type 2 diabetes in US adults. Combining 3 large cohorts, they found 12 611 cases of type 2 diabetes during 3 645 585 person-years of follow-up. Consumption of anthocyanin-rich foods, particularly blueberries and apples/pears, was associated with a lower risk of type 2 diabetes. No significant associations were found for total flavonoid intake or other flavonoid subclasses.
Muraki et al28 determined whether fruit consumption and risk of type 2 diabetes were linked by combining results from 3 longitudinal cohort studies. They reported differences among the individual fruits. Greater consumption of specific whole fruits, particularly blueberries, grapes, and apples/pears, is significantly associated with a lower risk of type 2 diabetes, whereas greater consumption of fruit juice is associated with a higher risk.
A 2015 systematic review of the health benefits of pears suggested that their laxative effect comes from their high fiber and fructose content. Fructose is a naturally occurring sugar that occurs in most fruits.
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