Article pubs.acs.org/JAFC
Fast Estimation of Dietary Fiber Content in Apple Sophie Le Gall,* Sonia Even, and Marc Lahaye INRA, UR1268 Biopolymères Interactions Assemblages, rue de la Géraudière, F-44316 Nantes, France S Supporting Information *
ABSTRACT: Dietary fibers (DF) are one of the nutritional benefits of fleshy fruit consumption that is becoming a quality criterion for genetic selection by breeders. However, the AOAC total DF content determination is not readily amenable for screening large fruit collections. A new screening method of DF content in an apple collection based on the automated preparation of cell wall material as an alcohol-insoluble residue (AIR) is proposed. The yield of AIR from 27 apple genotypes was compared with DF measured according to AOAC method 985.29. Although residual protein content in AIRs did not affect DF measurement, subtraction of starch content above 3% dry weight in AIRs was needed to agree with AOAC measured DF. A fast colorimetric screening of starch in AIR was developed to detect samples needing correction. The proposed method may prove useful for the rapid determination of DF in collections of other fleshy fruit besides apple. KEYWORDS: phenotyping, food quality, nonstarch polysaccharides, fruit
■
INTRODUCTION Public authorities highly encourage fruit consumption for their health benefits as major contributors to alleviate civilization diseases associated with Western diets (diabetes, cancers, cardiovascular diseases, stroke, obesity, hypertension).1−6 To accompany nutritional policies, fruit organoleptic and nutritional qualities need to meet consumer demand. To that aim, besides classical selection criteria, such as resistance to biotic and abiotic stress, production yields, and postharvest handling and preservation, breeders and growers are becoming increasingly concerned with fruit quality. Quality criteria encompass fruit appearance, flavor, texture, and now-a-days nutritionally important components, such as dietary fibers, antioxidants, vitamins, and other nutraceutic compounds.7−10 Since the 1980s, dietary fibers have been recognized as being major components in the health benefits associated with plant foods. Due to their physicochemical properties, they also demonstrate functional characteristics of interest as food ingredients.11,12 Dietary fibers are defined as “the remnants of edible plant cells, polysaccharides, lignin, and associated substances resistant to digestion by the alimentary enzymes of humans” to which was later added resistant starch and low molecular weight molecules, such as purified or synthesized carbohydrates “which have been shown to have a physiological effect of benefit to health as demonstrated by generally accepted scientific evidence to competent authorities”.13−15 At first, two methods for measuring dietary fibers were developed, the enzymatic−gravimetric method, which targeted polysaccharides, part of resistant starch and lignin, and the enzymatic−chemical method, which focused on the chemical analyses of nonstarch polysaccharide (NSP) monomers.16−19 Both methods were based on the enzymatic removal of starch, which is difficult in starch-rich foods, such as rice, white bread, or potatoes containing little NSP. Since then, the enzymatic− gravimetric method has undergone many changes and revisions to meet the AACCI/AOAC standards (AACCI 32-05.01/ AOAC 985.29, AACCI 32-45.01/AOAC 2009.1, and AACCI 32-50.01/AOAC 2011.25).15,20 The last modifications pro© XXXX American Chemical Society
posed were to better accommodate the poorly assayed low molecular weight dietary fibers in the former methods and to avoid overestimating some compounds, such as maltodextrins.21,22 Other revisions were proposed to better measure starch glucose, such as by adding a second amyloglucosidase digestion step or by the use of a new enzyme more effective in degrading starch.23,24 All of these evolutions demonstrate that the accuracy of dietary fibers measuring methods is still at the heart of concerns. However, although these methods are gaining in accuracy, they remain time-consuming and not readily amenable for large-scale screening studies, such as fruit genetic collections. To that end, we devised a method allowing rapid estimation of dietary fiber content in a collection of apples to provide breeders and plant scientists with a high-throughput mean of screening and grading fruit genotypes and crops on a key nutritional characteristic. Our strategy was based on the facts that cell wall polysaccharides represent the majority of fruit dietary fibers and that starch, and especially resistant starch, for which many assay improvements have been recently made is not an important issue in most fleshy fruits harvested, such as apple. Our objective in this study was to evaluate an automatized cell wall preparation as alcohol-insoluble residue (AIR) as a means to estimate dietary fiber content. We also developed a rapid test to screen AIR for residual starch content that would require precise content measurement to better estimate dietary fiber content.
■
MATERIALS AND METHODS
Materials. Fruit. Twenty-seven experimental genotypes of apples (five fruits per genotype) were harvested and provided by IRHS, INRA (Angers, France). Two additional fruits used as references for the starch colorimetric assay were collected at INRA of Nantes: one Received: November 5, 2015 Revised: January 27, 2016 Accepted: January 27, 2016
A
DOI: 10.1021/acs.jafc.5b05301 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry
Figure 1. Comparison of AOAC dietary fiber content, AIR yield ± starch-corrected (expressed in % of initial dry weight (DW)) and protein and starch amounts in AIR (expressed in % of AIR DW). Arrows highlight samples for which a difference can be observed; asterisks, samples for which yields show a clear trend to differ, p value < 0.09 (∗), and significantly different p value < 0.05 (∗∗). The red line shows the starch threshold above which starch content in AIR affects the correlation with the AOAC fiber content. The red box delimits samples for which AIR yield needs to be corrected for starch content. starch-rich fruit was harvested before complete maturity and the other was harvested at maturity and stored for 2 months at 4 °C. Chemicals. Ethanol absolute anhydrous, hydrogen peroxide solution 30%, and potassium chloride were purchased from Carlo Erba. Iodine, potassium iodine, acetone, sodium dichloroisocyanurate, sodium salicylate, Brij L23, sodium hydroxide, rhamnose, and glucose were from Sigma-Aldrich. Selenium catalyst was from Thompson and Capper. Sodium nitroprusside, dihydrate, was from Merck and sulfuric acid from Fisher Scientific. Enzyme. α-Amylase, purified from Bacillus licheniformis (EBLAAM), and amyloglucosidase, from Aspergillus niger (E-AMGDF), were purchased from Megazyme (Bray, Ireland). Reference fiber, European Reference Material ERM-BC516, was obtained from IRMM (Geel, Belgium). Statistical Evaluation. All experiments were performed in triplicate or more (up to six repetitions for the AOAC dietary fiber content method). Data means were tested for equality with Student’s t test. Total Dietary Fiber (TDF) Measurement. AOAC Method. TDF was analyzed using a commercial kit based on AACC method 32-05.01 and AOAC method 985.29 (K-TDFR, Megazyme). Proposed Method. Peeled apple parenchyma cell wall polysaccharides were prepared as AIR using an automated extraction method with an accelerated solvent extraction unit ASE 350 (Thermo Scientific Dionex). Approximately 500 mg of frozen apple flesh was freeze-dried and then dried at 40 °C overnight under vacuum over P2O5. The dried material was ground into a fine powder using a FastPrep-24 instrument (MP Biochemicals) at a speed of 6.5 m s−1 for 60 s. Samples (500 mg) were extracted using 80% ethanol at a flow rate of 2 mL min−1 in 22 mL cells of the ASE 350. The conditions for the ASE extraction were set at 100 °C with a flow time of 6 min, followed by a rinse with a volume of 150%, and a purge time (N2) of 30 s. AIRs were dried at 40 °C overnight under vacuum over P2O5 before grinding and weighing. AIR yield (%) as fiber determination was computed as the difference between freeze-dried apple flesh and AIRs.
The results are expressed in percent of the raw material dry weight. An international apple fiber standard, ERM -BC516, which consists of dry apple material, was use as a reference in these two methods. Protein Content Determination. Protein levels were calculated as total nitrogen contents, determined by the Kjeldahl method, multiplied by the conversion factor 6.25.25 Briefly, 40 mg of dried material was mineralized with appropriate reagents (sulfuric acid 95%, selenium catalyst mixture, and hydrogen peroxide solution 30%) at a range of temperatures from 70 to 350 °C using a Kjeldatherm system (C. Gerhardt GmbH & Co.). The ammonium released was measured at 630 nm as a blue-green colored complex with sodium salicylate and chlorine under alkaline conditions, using an automatic photometric system (AutoAnalyzer System, Bran+Luebbe, GmbH). Starch Content Measurement. Amylolysis and HPAEC Analyses. Glucose from residual starch in the AIR was measured after amylolysis.26 AIR (10 mg) was incubated overnight at room temperature in 200 μL of MOPS (50 mM, pH7) followed by 5 min at 120 °C. Commercial thermostable α-amylase from B. licheniformis (Megazyme, 3000 U mL−1) was added, and the sample was incubated for a further 6 min at 100 °C. After cooling, the sample was adjusted to pH 4.5 by the addition of 400 μL of acetate buffer (200 mM, pH 4.5). It was further incubated for 30 min at 50 °C with commercial amyloglucosidase (Megazyme, 3300 U mL−1). Glucose released was quantified in HPAEC-PAD (ICS-3000, Thermo Scientific Dionex) using a CarboPac PA1 column (2 mm × 250 mm, Thermo Scientific, USA), thermostated at 25 °C. An isocratic elution of 500 mM of NaOH was used at a flow rate 0.25 mL min−1. Rhamnose was used as an internal standard for calibration. Starch Evaluation by Colorimetric Assay. Reference AIRs containing a range from 0.4 to 13.1% dry weight of starch were prepared by combining the AIR of an immature apple containing 40% starch to another from fruit stored in the cold for 2 months and containing 0.4% starch. Ten milligrams of each AIRs (reference and samples) was precisely weighed in a 96-well microplate. Eight hundred microliters of iodine solution (I2/IK, 0.1%/1%) was added followed by 100 μL of acetone. B
DOI: 10.1021/acs.jafc.5b05301 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry
Table 1. Student t Test Probabilities between Total Dietary Fiber Mean Values Obtained According to the AOAC Method and the Proposed AIR Method without and with Starch Correctiona
The microplate was gently agitated briefly and centrifuged for 30 s at 3000g. A scan of the microplate bottom was done using an Image Scanner III (GE Healthcare) at a resolution of 300 and 100 lx. The gray level of each reference and sample AIR containing well was determined (ImageJ, http://imagej.nih.gov/ij). Estimation of starch within AIR samples was realized using the standard curve plotted with the reference AIRs.
probability
■
RESULTS AND DISCUSSION Comparison of AIR Yield and Dietary Fiber Content Measured by the AOAC Method. As a first step, cell wall material was rapidly prepared as an AIR using an automated solvent extractor. The parameters used for apple raw material were defined previously in the laboratory and recently published.27 They allow obtaining a material free from sugars (i.e., the sum of glucose, fructose, and sucrose amounts is 0.09). whereas 2 (X2838, X8405) exhibited a significant difference (p value < 0.05) and 1 (X4388) was just above the 0.05 limit (p value = 0.086; Table 1). Additionally, it is also interesting to note that the AIR yield means and median standard deviations (both at 0.27) were about half those of the fiber contents obtained using the AOAC method (0.61 and 0.55, respectively), confirming the repeatability and reproducibility of the proposed method. Starch Impact on AIR Yield and Dietary Fiber Content. It is well-known that the amylolytic and proteolytic enzymes in the AOAC method used in this study do not eliminate all forms of starch and proteins. This is why residual proteins are measured separately and their content is subtracted from the crude fiber estimated gravimetrically. On the other hand, cell wall prepared in the form of AIR is known to contain starch, if present in the tissue, and part of the cell proteins, particularly those tightly bonded to cell wall polymers or precipitated by hot ethanol. Apples are usually harvested at a physiological stage when starch regression is well underway and completed after storage. Depending on apple variety, residual starch content is usually low when the fruit is consumed.29 To evaluate the impact of starch and proteins on AIR yields and AOAC fiber measurements, starch and protein contents were determined after amylolysis and from total nitrogen content, respectively.25 The results show that the levels of
sample
uncorrected for starch
corrected for starch
V22 X1344 X8737 X157 V31 V41 X8414 X9267 X8413 X1682 H42 C068 W6 I41 X9190 X9394 X2990 I94 X8703 W101 X129 X8391 I49 W43 X4388 X8405 X2838
0.220 0.735 0.391 0.985 0.856 0.817 0.620 0.986 0.902 0.410 0.662 0.255 0.712 0.896 0.914 0.095 0.668 0.887 0.305 0.900 0.602 0.125 0.236 0.963 0.086 0.021 0.002
0.224 0.756 0.359 0.954 0.813 0.760 0.592 0.832 0.986 0.671 0.453 0.377 0.976 0.626 0.780 0.230 0.368 0.661 0.634 0.800 0.921 0.450 0.793 0.525 0.565 0.719 0.123
Above 0.05, the mean total dietary fibers measured by the two methods did not differ. a
starch and protein in AIR had median values of 1.4 and 4.8%, respectively, and are genotype-dependent (Figure 1). Starch content varied from 0.2 to 9.2%, whetrsd that of proteins varied from 2.8 to 7.9%. Interestingly, the difference observed for the fiber content of the three samples (X2838, X8405, and X4388) was related to starch content (Figure 1). Indeed, these genotypes were also those measured with the highest starch content of the apple collection (≥4% DWAIR). To confirm the impact of starch content in AIR on the correlation with the AOAC dietary fiber measurements, each AIR yield was corrected by subtracting its accurate starch value (Figure 1). Focusing on samples for which starch content was >2.5% of AIR dry weight, the corrected yields showed a better agreement with dietary fibers measured with the AOAC method (Figure 1 and Table 1). It should be noted that whereas there was no significant difference found between the AIR content and the AOAC dietary fiber value of samples whose starch content was between 3 and 4% (X8391, I49, and W43), probably due to the high standard deviation of the AOAC values (Figure 1), correction of AIR for starch particularly improved the agreement with the AOAC fiber values. Surprisingly, no difference was found between AIR yield and dietary fiber content due to protein (Figure 1). The amount of proteins remaining in AIRs did not affect the good agreement with the dietary fiber values measured by the AOAC method. C
DOI: 10.1021/acs.jafc.5b05301 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry
Figure 2. RGB image of the 96-well microplate of the references (A) and AIR samples tested (B) using the fast colorimetric assay to highlight (in red) AIR samples with starch content ≥3%/DWAIR. (Inset) Standard curve plotting reference AIR color intensity versus starch content.
Workflow for Total Dietary Fiber Screening in Fruit Collections. The workflow of the dietary fiber screening method proposed is (1) automatic AIR preparation and calculation of AIR extraction yields, (2) identification of AIRs in which the content in starch is ≥3% dry weight as determined by the fast colorimetric method, (3) determination of the accurate starch content if ≥3% using amylase/amyloglucosidase digestion and quantification of glucose released by HPAEC, and (4) calculation of dietary fiber content using AIR yields ± corrected by starch content and expressed on the wet weight basis of the sample prior to freeze-drying. According to the present method, the fruit DF content varied from 9.4 to 14.3% on the DW basis and from 1.7 to 2.8% on the sample fresh weight (FW) in the range of published values.32,33 The order of genotypes according to the DF content differed between DW and FW, demonstrating likely differences in cells and/or cell wall amounts in the samples resulting from genetic and/or growth conditions. The method proposed is adapted for screening large fruit collections because AIR preparation, which proves to be highly repeatable and reproducible, requires for apple about 11 min per sample. Furthermore, AIR samples needing further accurate starch content analysis can be rapidly identified using the colorimetric assay developed in this study (∼1 h/40 samples). To conclude, the proposed method was tested and validated on apple but can be extended to other types of fleshy fruit and fruit transformation byproducts, such as tomato, grape, peach, or fruit pomaces, considering possible adjustments for the automatic AIR preparation. HPLC measurement of nondigestible oligosaccharide content in the ethanol extract may also prove useful to reach better dietary fiber estimates in some of these food products.34 In the case of starchy fruit, such as banana, the initial tissue amount sampled may have to be increased to improve the precision of dietary fiber content.
This may be related to the method of AIR preparation. The raw material was heated in 80% ethanol at 100 °C, and the extraction was performed under pulses of high pressure (100 bar maximum). Compounds assayed by the gravimetric method may have been removed by these conditions and compensated by the remaining proteins. Thus, these results show that even in apple where starch is a minor component, it is important to correct AIR yield with starch content when it represents at least 3% AIR dry weight. For most apple samples this correction will not usually be necessary, and thus the time-consuming measurement for accurate starch content can be avoided. However, to check rapidly samples that would require correction, we developed a colorimetric screening procedure based on an iodine test. Fast Estimation of Starch Content in Apple by Colorimetric Assay. This assay uses the property of starch to form colored complexes with iodine that is used to follow starch regression in fruit and to determine amylose/ amylopectin contents in starchy products by spectrophotometry.29,30 In contrast to the conventional spectrophotometric assay, which needs starch solubilization and uses up to six wavelengths, the proposed method is based on the color intensity of iodine bond AIR captured by an Image Scanner. The intensity of this coloration depends on the amount of starch present in the AIR as well as that of hemicellulose (xyloglucan).31 To take into account the cell wall polysaccharide interference, a standard curve was realized by combining apple AIRs of different starch contents, that is, from an immature apple (starch content of 40%/DWAIR) and from an apple stored for 2 months (starch, i.e., 0.4%/DWAIR). Seven starch concentrations from ∼0 to ∼13%/DWAIR were realized and accurately measured by the enzymatic−HPAEC method.26 Iodine was then added to this 7-point range in a 96-well microplate and scanned as described above. The gray levels of this 7-point range were plotted against the accurate starch content to produce the standard curve (Figure 2). Comparing the gray levels obtained from the AIR iodine complex of the apple collection allowed the rapid identification of samples for which starch content was likely to exceed 3%/DWAIR. In this example, 8 samples were highlighted (W101, X129, X8391, I49, W43, X4388, X8405, and X2838; Figure 2) and were found to contain from 2.3 to 9.2% starch as determined by the enzymatic−HPAEC method.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.5b05301. Supplementary Table 1, dietary fiber content measured or estimated using the classical AOAC method (fiber (AOAC)) or the fast method (AIR and starch-corrected AIR) for 27 apple genotypes (PDF) D
DOI: 10.1021/acs.jafc.5b05301 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry
■
method and interpreting results. Anal. Bioanal. Chem. 2013, 405, 4359−4372. (16) Prosky, L.; Asp, N. G.; Schweizer, T. F.; DeVries, J. W.; Furda, I. Determination of insoluble, soluble, and total dietary fiber in foods and food products: interlaboratory study. J. Assoc. Off. Anal. Chem. 1988, 71, 1017−1023. (17) Prosky, L.; Asp, N. G.; Schweizer, T. F.; DeVries, J. W.; Furda, I.; Lee, S. C. Determination of soluble dietary fiber in foods and food products: collaborative study. J. AOAC Int. 1994, 77, 690−694. (18) Englyst, H. N.; Cummings, J. H. Improved method for measurement of dietary fiber as non-starch polysaccharides in plant foods. J. Assoc. Off. Anal. Chem. 1988, 71, 808−814. (19) Englyst, H. N.; Quigley, M. E.; Hudson, G. J. Determination of dietary fibre as non-starch polysaccharides with gas-liquid chromatographic, high-performance liquid chromatographic or spectrophotometric measurement of constituent sugars. Analyst 1994, 119, 1497− 1509. (20) AOAC International Official Methods 985.29, 991.42, 991.43, 999.03, 993.19, 997.08, 999.03, 2000.11, 2001.02, 2001.03, 2002.02, and 2009.01; AOAC International: Gaithersberg, MD, USA, 2005. (21) Mccleary, B. V. Modification to AOAC official methods 2009.01 and 2011.25 to allow for minor overestimation of low molecular weight soluble dietary fiber in samples containing starch. J. AOAC Int. 2014, 97, 896−901. (22) McCleary, B. V.; DeVries, J. W.; Rader, J. I.; Cohen, G.; Prosky, L.; Mugford, D. C.; Okuma, K. Determination of insoluble, soluble, and total dietary fiber (CODEX definition) by enzymatic-gravimetric method and liquid chromatography: collaborative study. J. AOAC Int. 2012, 95, 824−844. (23) Brunt, K.; Sanders, P. Improvement of the AOAC 2009.01 total dietary fibre method for bread and other high starch containing matrices. Food Chem. 2013, 140, 574−580. (24) Tanabe, K.; Nakamura, S.; Oku, T. Inaccuracy of AOAC method 2009.01 with amyloglucosidase for measuring non-digestible oligosaccharides and proposal for an improvement of the method. Food Chem. 2014, 151, 539−546. (25) Jones, J. B. Kjeldahl Method for Nitrogen Determination; MicroMacro Publishing: Athens, GA, USA, 1991. (26) McCleary, B. V.; Gibson, T. S.; Mugford, D. C. Measurement of total starch in cereal products by amyloglucosidase-α-amylase method: collaborative study. J. AOAC Int. 1997, 80, 571−579. (27) Winisdorffer, G.; Musse, M.; Quellec, S.; Devaux, M. F.; Lahaye, M.; Mariette, F. MRI investigation of subcellular water compartmentalization and gas distribution in apples. Magn. Reson. Imaging 2015, 33, 671−680. (28) Muir, J. G.; Rose, R.; Rosella, O.; Liels, K.; Barrett, J. S.; Shepherd, S. J.; Gibson, P. R. Measurement of short-chain carbohydrates in common Australian vegetables and fruits by highperformance liquid chromatography (HPLC). J. Agric. Food Chem. 2009, 57, 554−565. (29) Hulme, A. C. Some aspects of the biochemistry of apple and pear fruits. Adv. Food Res. 1958, 8, 297−413. (30) Jarvis, C. E.; Walker, J. R. L. Simultaneous, rapid, spectrophotometric determination of total starch, amylose and amylopectin. J. Sci. Food Agric. 1993, 63, 53−57. (31) Kooiman, P. A method for the determination of amyloid in plant seeds. Recl. Trav. Chim. Pays Bas 1960, 79, 675−678. (32) Gheyas, F.; Blankenship, S. M.; Young, E.; McFeeters, R. Dietary fibre content of thirteen apple cultivars. J. Sci. Food Agric. 1997, 75, 333−340. (33) Englyst, H. N.; Quigley, M. E.; Hudson, G. J.; Cummings, J. H. Determination of dietary fibre as non-starch polysaccharides by gasliquid chromatography. Analyst 1992, 117, 1707−1714. (34) Jovanovic-Malinovska, R.; Kuzmanova, S.; Winkelhausen, E. Application of ultrasound for enhanced extraction of prebiotic oligosaccharides from selected fruits and vegetables. Ultrason. Sonochem. 2015, 22, 446−453.
AUTHOR INFORMATION
Corresponding Author
*(S.L.G.) Phone: +33 1 (0)2 40 67 50 98. E-mail:
[email protected]. Funding
This work was financed and was partly funded under the EU Seventh Framework Programme by FruitBreedomics Project 265582: Integrated Approach for Increasing Breeding Efficiency in Fruit Tree Crop. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS We thank IRHS (Institut de Recherche en Horticulture et Semences), INRA, Angers, France, for providing fruit.
■
REFERENCES
(1) He, F. J.; Nowson, C. A.; MacGregor, G. A. Fruit and vegetable consumption and stroke: meta-analysis of cohort studies. Lancet 2006, 367, 320−326. (2) Key, T. J. Fruit and vegetables and cancer risk. Br. J. Cancer 2011, 104, 6−11. (3) Slavin, J. L.; Lloyd, B. Health benefits of fruits and vegetables. Adv. Nutr. 2012, 3, 506−516. (4) Boeing, H.; Bechthold, A.; Bub, A.; Ellinger, S.; Haller, D.; Kroke, A.; Leschik-Bonnet, E.; Müller, M. J.; Oberritter, H.; Schulze, M.; Stehle, P.; Watzl, B. Critical review: vegetables and fruit in the prevention of chronic diseases. Eur. J. Nutr. 2012, 51, 637−663. (5) Bradbury, K. E.; Appleby, P. N.; Key, T. J. Fruit, vegetable, and fiber intake in relation to cancer risk: findings from the European Prospective Investigation into Cancer and Nutrition (EPIC). Am. J. Clin. Nutr. 2014, 100 (Suppl. 1), 394S−398S. (6) Rautiainen, S.; Wang, L.; Lee, I. M.; Manson, J. E.; Buring, J. E.; Sesso, H. D. Higher intake of fruit, but not vegetables or fiber, at baseline is associated with lower risk of becoming overweight or obese in middle-aged and older women of normal BMI at baseline. J. Nutr. 2015, 145, 960−968. (7) Bliss, F. A. Nutritional improvement of horticultural crops through plant breeding. HortScience 1999, 34, 1163−1167. (8) Patil, B. S.; Crosby, K.; Byrne, D.; Hirschi, K. The intersection of plant breeding, human health, and nutritional security: lessons learned and future perspectives. HortScience 2014, 49, 116−127. (9) Verdu, C. F.; Guyot, S.; Childebrand, N.; Bahut, M.; Celton, J. M.; Gaillard, S.; Lasserre-Zuber, P.; Troggio, M.; Guilet, D.; Laurens, F. QTL analysis and candidate gene mapping for the polyphenol content in cider apple. PLoS One 2014, 9, e107103. (10) Farneti, B.; Masuero, D.; Costa, F.; Magnago, P.; Malnoy, M.; Costa, G.; Vrhovsek, U.; Mattivi, F. Is there room for improving the nutraceutical composition of apple? J. Agric. Food Chem. 2015, 63, 2750−2759. (11) Elleuch, M.; Bedigian, D.; Roiseux, O.; Besbes, S.; Blecker, C.; Attia, H. Dietary fibre and fibre-rich by-products of food processing: characterisation, technological functionality and commercial applications: a review. Food Chem. 2011, 124, 411−421. (12) Dhingra, D.; Michael, M.; Rajput, H.; Patil, R. T. Dietary fibre in foods: a review. J. Food Sci. Technol. 2012, 49, 255−266. (13) Trowell, H. Definition of dietary fiber and hypotheses that it is a protective factor in certain diseases. Am. J. Clin. Nutr. 1976, 29, 417− 427. (14) Codex Alimentariou Commission. Report from the thirtysecond meeting of the Codex Alimentarius Commission; FAO: Rome, Italy, 2009; available at http://www.codexalimentarius.org/meetingsreports/en/?sortingDate=%C2%B012009. (15) Zielinski, G.; Rozema, B. Review of fiber methods and applicability to fortified foods and supplements: choosing the correct E
DOI: 10.1021/acs.jafc.5b05301 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
