Seasonal Variability of the Phytochemical Composition of New Red-Fleshed Apple Varieties Compared with Traditional and New White-Fleshed Varieties

Image analysis and polyphenol profiling unveil red-flesh apple phenotype complexity

BACKGROUND

The genetic basis of colour development in red-flesh apples (Malus domestica Borkh) has been widely characterised; however, current models do not explain the observed variations in red pigmentation intensity and distribution. Available methods to evaluate the red-flesh trait rely on the estimation of an average overall colour using a discrete class notation index. However, colour variations among red-flesh cultivars are continuous while development of red colour is non-homogeneous and genotype-dependent. A robust estimation of red-flesh colour intensity and distribution is essential to fully capture the diversity among genotypes and provide a basis to enable identification of loci influencing the red-flesh trait.

RESULTS

In this study, we developed a multivariable approach to evaluate the red-flesh trait in apple. This method was implemented to study the phenotypic diversity in a segregating hybrid F1 family (91 genotypes). We developed a Python pipeline based on image and colour analysis to quantitatively dissect the red-flesh pigmentation from RGB (Red Green Blue) images and compared the efficiency of RGB and CIEL*a*b* colour spaces in discriminating genotypes previously classified with a visual notation. Chemical destructive methods, including targeted-metabolite analysis using ultra-high performance liquid chromatography with ultraviolet detection (UPLC-UV), were performed to quantify major phenolic compounds in fruits' flesh, as well as pH and water contents. Multivariate analyses were performed to study covariations of biochemical factors in relation to colour expression in CIEL*a*b* colour space. Our results indicate that anthocyanin, flavonol and flavanol concentrations, as well as pH, are closely related to flesh pigmentation in apple.

CONCLUSTION

Extraction of colour descriptors combined to chemical analyses helped in discriminating genotypes in relation to their flesh colour. These results suggest that the red-flesh trait in apple is a complex trait associated with several biochemical factors.

The Effects of the Cultivar and Environment on the Phenolic Contents of Hazelnut Kernels

Different climatic conditions are known to affect the synthesis of primary and secondary metabolites. Therefore, the phenolic contents in new growing areas could affect the quality and flavor of hazelnuts. The aim of this study was to determine the variability of the phenolic contents of the kernels in different commercial hazelnut cultivars depending on their growing area. Five cultivars ('Tonda Gentile delle Langhe', 'Merveille de Bollwiller', 'Pauetet', 'Tonda di Giffoni', and 'Barcelona' (syn. 'Fertile de Coutard')) grown in different European collection orchards were included in the study. High-performance liquid chromatography coupled with mass spectrometry was used to identify and quantify the phenolic compounds. Thirteen phenols were identified in the hazelnut kernels, including 7 flavanols, 2 hydroxybenzoic acids, 3 flavonols, and one dihydrochalcone. Catechin and procyanidin dimers were the main phenolic compounds found in the hazelnut kernels. The highest contents of catechin and total flavanols were determined in cultivars cultivated in Spain and northern Italy, and the lowest in Slovenia and France. Flavanols were the major phenolic groups independent of the place of cultivation, as they accounted for more than 50% of all phenolic compounds identified. The flavanols were followed by hydroxybenzoic acids, flavonols, and dihydrochalcones. Higher contents of flavanols and flavonols were found in kernels from areas characterized by higher natural irradiation, which stimulates their accumulation. The contents of hydroxybenzoic acids correlated with altitude, which stimulated phenolic acid synthesis. A negative correlation was observed between the dihydrochalcone content and annual rainfall, probably due to hydric stress.

Polyphenols from Thinned Young Apples: HPLC-HRMS Profile and Evaluation of Their Anti-Oxidant and Anti-Inflammatory Activities by Proteomic Studies

The qualitative profile of thinned apple polyphenols (TAP) fraction (≈24% of polyphenols) obtained by purification through absorbent resin was fully investigated by LC-HRMS in positive and negative ion mode and using ESI source. A total of 68 polyphenols were identified belonging to six different classes: flavanols, flavonols, dihydrochalchones, flavanones, flavones and organic and phenolic acids. The antioxidant and anti-inflammatory activities were then investigated in cell models with gene reporter for NRF2 and NF-κB and by quantitative proteomic (label-free and SILAC) approaches. TAP dose-dependently activated NRF2 and in the same concentration range (10–250 µg/mL) inhibited NF-κB nuclear translocation induced by TNF-α and IL-1α as pro-inflammatory promoters. Proteomic studies elucidated the molecular pathways evoked by TAP treatment: activation of the NRF2 signaling pathway, which in turn up-regulates protective oxidoreductases and their nucleophilic substrates such as GSH and NADPH, the latter resulting from the up-regulation of the pentose phosphate pathway. The increase in the enzymatic antioxidant cellular activity together with the up-regulation of the heme-oxygenase would explain the anti-inflammatory effect of TAP. The results suggest that thinned apples can be considered as a valuable source of apple polyphenols to be used in health care products to prevent/treat oxidative and inflammatory chronic conditions.

New red-fleshed apple cultivars: a comprehensive review of processing effects, (poly)phenol bioavailability and biological effects

Red-fleshed apple cultivars with an enhanced content of anthocyanins have recently attracted the interest of apple producers and consumers due to their attractive color and promising added health benefits. In this paper, we provide the first comprehensive overview of new hybrid red-fleshed apples, mainly focusing on their (poly)phenolic composition, the effect of processing, the (poly)phenolic bioavailability and the biological effects. Evidence so far from in vitro and in vivo studies supports their added beneficial effects compared to common apples on health outcomes such as cancer, cardiovascular disease, inflammation and immune function, which are mainly related to their specific (poly)phenol composition.

Prevention and management of type II diabetes chronic complications: the role of polyphenols (Mini-Review)

The numerous complications of diabetes may be at least in part generated by the oxidative stress associated with the constant state of hyperglycemia. Polyphenols are plant based secondary metabolites that have high potentials in the prevention and treatment of some diseases, in particular those that involve oxidative stress, such as complications of diabetes. The purpose of this narrative review is to show the main evidence regarding the role of polyphenols in treating and preventing these complications. For the bibliographic research, the papers published up to March 15, 2021 were considered and the search terms included words relating to polyphenols, their classes and some more known compounds, in association with the complications of diabetes. There are numerous studies showing how polyphenols are active against endothelial damage induced by diabetes, oxidative stress and hyperinflammatory states that are at the origin of the complications of diabetes. Compounds such as flavonoids, but also anthocyanins, stilbenes or lignans slow the progression of kidney damage, prevent ischemic events and diabetic nephropathy. Many of these studies are preclinical, in cellular or animal models. The role of polyphenols in the prevention and treatment of diabetes complications is undoubtedly promising. However, more clinical trials need to be implemented to understand the real effectiveness of these compounds.

Extraction of Phenolic Compounds from Fresh Apple Pomace by Different Non-Conventional Techniques

Red Delicious apple pomace was produced at laboratory scale with a domestic blender and different non-conventional extraction techniques were performed to isolate phenolic compounds, such as ultrasound-assisted extraction (UAE), ultraturrax extraction (UTE), accelerated solvent extraction (ASE) and pulsed electric field (PEF) extraction pre-treatment. Total phenolic content (TPC) was determined by Folin-Ciocalteu assay. Phloridzin, the main phenolic compound in apples, was determined by chromatographic analysis Q-TOF-LC/MS. The results obtained with these techniques were compared in order to identify the most efficient method to recover polyphenols. The highest value of TPC (1062.92 ± 59.80 µg GAE/g fresh apple pomace) was obtained when UAE was performed with EtOH:H₂O (50:50, v/v), while ASE with EtOH:H₂O (30:70, v/v) at 40 °C and 50% of flush was the most efficient technique in the recovery of phloridzin. The concentration of the main phenolic compounds ranged from 385.84 to 650.56 µg/g fresh apple pomace. The obtained results confirm that apple pomace represents an interesti-ng by-product, due to the presence of phenolic compounds. In particular, phloridzin could be considered a biomarker to determine the quality of numerous apple products. Therefore, this research could be a good starting point to develop a value-added product such as a functional food or nutraceutical.

Apple Fermented Products: An Overview of Technology, Properties and Health Effects

As an easily adapted culture, with overloaded production in some parts of the globe, apples and their by-products are being redirected to pharmaceutical, canning and beverages industries, both alcoholic and non-alcoholic. Fermentation is generally considered to increase the bioavailability of bioactive compounds found in apple, by impacting, through a high degree of changes, the product’s properties, including composition and health-promoting attributes, as well as their sensory profile. Probiotic apple beverages and apple vinegar are generally considered as safe and healthy products by the consumers. Recently, contributions to human health, both in vivo and in vitro studies, of non-alcoholic fermented apple-based products have been described. This review highlighted the advances in the process optimization of apple-based products considering vinegar, cider, pomace, probiotic beverages and spirits’ technologies. The different processing impacts on physical-chemical, nutritional and sensory profiles of these products are also presented. Additionally, the harmful effects of toxic compounds and strategies to limit their content in cider and apple spirits are illustrated. New trends of fermented apple-based products applicability in tangential industries are summarized.

Untargeted Screening in a Case Control Study Using Apples as a Matrix

Untargeted screening using high resolution mass spectrometry (HRMS) is a promising approach for screening the food supply for contaminants, but the sheer amount of information inherent to the HRMS data set presents analytical challenges. Red apples, collected during the U.S. FDA's Total Diet Study, were studied to determine whether bioinformatic software can be used to distinguish spiked model compounds from those native to apples. A workflow was created, in which initial data sets of over 44,000 features in each of the two spiked samples were reduced by several orders of magnitude to a scale suitable for visual inspection. After visual inspection to address degeneracy and data quality, the final data sets contained 30 and 2 suspect compounds, respectively. To the best of our knowledge, this is the largest scale case-control study on food matrices to date and the first use of market basket samples as references in an untargeted screening study.

Fruit Sector Strategic Management: An Exploration of Agro-food Chain Actors’ Perception of Market Sustainability of Apple Innovation

The fresh fruit industry is a highly dynamic sector in the food market. Fresh fruit chain actors have to adapt to the changing market environment in order to face upcoming challenges. The objective of this study is to analyze the market sustainability of red-fleshed apples (RFA) by exploring consumers’ and fresh fruit industry experts’ and stakeholders’ opinions in Italy and New Zealand. The study was carried out in Italy and New Zealand from December 2018 to June 2019 including 778 consumers and 29 expert and stakeholder interviews. Results show a promising market potential of RFA. Innovative attributes and nutritional value of RFA are the most important factors that push consumers’ interest and willingness to buy RFA. New Zealand consumers and women show a higher appreciation of RFA. The nutritional value of the fruit can be a strategic marketing management attribute especially for health-conscious consumers. However, experts think the market for RFA will develop slowly, and will remain a niche product. Some stakeholders are skeptical about consumer RFA appreciation, and fear that RFA are too radical a novelty on the market. The RFA may be perceived as not natural. There is the need to coordinate food chain stakeholders’ management practices on RFA. This allows to mitigate risks, set food standards acceptable for all chain stakeholders, and make sustainable economic investment on innovation.

Consumption evaluation of one apple flesh a day in the initial phases prior to adenoma/adenocarcinoma in an azoxymethane rat colon carcinogenesis model

Colorectal cancer (CRC) is the fourth cancer with the most new cases reported in 2018 worldwide. Consumption of fruit and vegetables is a protective factor against the risk of CRC. Beyond this, flavonoids could orchestrate these healthy effects. Apart from containing the typical apple flavonoids, red-fleshed apples also contain anthocyanins, mainly cyanidin-3-O-galactoside (Cy3Gal). Through an azoxymethane rat carcinogenesis model, a study was carried out in order to assess the possible protective effects of apple polyphenols, with special attention to anthocyanins. In addition, apart from negative and positive controls, a group with chemotherapy with 5-fluorouracil (5FU) was included to compare their performance against the output collected from the animal treatments with white-fleshed apple (WF), red-fleshed apple (RF) and Cy3Gal (AE). Although the 5FU group presented the best performance towards aberrant crypt foci (ACF) inhibition (70.1%), rats fed with white-fleshed apples ('Golden Smoothee') were able to achieve 41.3% ACF inhibition, while none of the challenged treatments (WF, RF and AE) suffered mucin depletion in their colonocytes. Expression changes of 17 genes related to CRC were assessed. In detail, the ACF inhibition phenotype detected in 5FU and WF groups could be explained through the expression changes detected in the apoptosis-related genes of Aurka, p53 and Cox2. Moreover, in the apple consumption groups (WF and RF), a reduced protein expression of matrix metalloproteinases with gelatinase activity (MMP-2 and 9) was detected. Overall, our study suggests an effect of apple polyphenols and apple anthocyanin Cy3Gal against colon carcinogenesis, retarding/diminishing the appearance of the precancerous markers studied.

Involvement of MdUGT75B1 and MdUGT71B1 in flavonol galactoside/glucoside biosynthesis in apple fruit

Apple is rich in flavonol glycosides, which are believed to contribute to putative health benefits associated with apple consumption. Glycosylation, catalyzed by uridine diphospho-glycosyltransferases (UGTs), is the last step in flavonol biosynthesis, which confers molecular stability and solubility to the flavonol. In the present study, the involvement of two UGTs, MdUGT75B1 and MdUGT71B1, in flavonol biosynthesis in apple was investigated. The major flavonols are quercetin 3-O-glycosides, and UV-B and blue light treatment significantly enhanced the accumulation of quercetin 3-O-galactoside, quercetin 3-O-glucoside, and kaempferol 3-O-galactoside. Transcript levels of MdUGT75B1 and MdUGT71B1 in fruit subjected to different treatments were correlated well with flavonol accumulation. MdUGT75B1 showed flavonol-specific activity with a preference for UDP-galactose as the sugar donor, while MdUGT71B1 using UDP-glucose exhibited a wider substrate acceptance. Thus, MdUGT75B1 and MdUGT71B1 are key UGTs involved in flavonol biosynthesis and may have important roles in regulating accumulation of these health-promoting bioactive compounds in apple.

Effect of Nanocrystallization of Anthocyanins Extracted from Two Types of Red-Fleshed Apple Varieties on Its Stability and Antioxidant Activity

Red-fleshed apple (Malus sieversii f. neidzwetzkyana (Dieck) Langenf) has attracted more and more attention due to its enriched anthocyanins and high antioxidant activity. In this study we extracted total anthocyanins and phenols from two types of red-fleshed apples-Xinjing No.4 (XJ4) and Red Laiyang (RL)-to study the stability and antioxidant activity of anthocyanins after encapsulation onto Corn Starch Nanoparticles (CSNPs). The results indicated the anthocyanins and total phenol levels of XJ4 were 2.96 and 2.25 times higher than those of RL respectively. The anthocyanin concentration and loading time had a significant effect on CSNPs encapsulation, and XJ4 anthocyanins always showed significantly higher loading capacity than RL. After encapsulation, the morphology of RL-CSNPs and XJ4-CSNPs was still spherical with a smooth surface as CSNPs, but the particle size increased compared to CSNPs especially for RL-CSNPs. Different stress treatments including UV light, pH, temperature, and salinity suggested that XJ4-CSNPs exhibited consistently higher stability than RL-CSNPs. A significantly enhanced free radical scavenging rate under stress conditions was observed, and XJ4-CSNPs had stronger antioxidant activity than RL-CSNPs. Furthermore, XJ4-CSNPs exhibited a slower released rate than RL-CSNPs in simulated gastric (pH 2.0) and intestinal (pH 7.0) environments. Our research suggests that nanocrystallization of anthocyanins is an effective method to keep the anthocyanin ingredients intact and active while maintaining a slow release rate. Compared to RL, encapsulation of XJ4 anthocyanins has more advantages, which might be caused by the significant differences in the metabolites of XJ4. These findings give an insight into understanding the role of nanocrystallization using CSNPs in enhancing the antioxidant ability of anthocyanins from different types of red-fleshed apples, and provide theoretical foundations for red-fleshed apple anthocyanin application.