Visualizing the structural and chemical heterogeneity of fruit and vegetables using advanced imaging techniques: fundamentals, instrumental aspects, applications and future perspectives.

Fruit and vegetables (F&V) are vastly complicated products with highly diverse chemical and structural characteristics. Advanced imaging techniques either combine imaging with spectral information or can provide excellent tissue penetration, and enable the possibility to target, visualize and even qualify the chemical and physical (structural) heterogeneity within F&V. In this review, visible and/or near infrared hyperspectral imaging, Fourier transform infrared microspectroscopic imaging, Raman imaging, X-ray and magnetic resonance imaging to reveal chemical and structural information in a spatial context of F&V at the macro- (entire products), meso- (tissues), and micro- (individual cells) scales are comprehensively summarized.

A-type proanthocyanidins: Sources, structure, bioactivity, processing, nutrition, and potential applications.

A-type proanthocyanidins (PAs) are a subgroup of PAs that differ from B-type PAs by the presence of an ether bond between two consecutive constitutive units. This additional C-O-C bond gives them a more stable and hydrophobic character. They are of increasing interest due to their potential multiple nutritional effects with low toxicity in food processing and supplement development.

Fate of Amadori compounds in processing and digestion of multi-ingredients tomato based sauces and their effect on other microconstituents.

Amadori compounds (ACs), the first stable products of Maillard reaction, are detected in various products of fruits and vegetables, and show an antioxidant activity which can be related to beneficial effects in human health. In order to optimize the nutritional quality of a multi-ingredient tomato sauce (tomato puree - onion - olive oil - dried pepper), the fate of ACs during processing (drying, heating) and gastrointestinal digestion of a model meal was assessed as well as that of other microconstituents, i.e.

Plant leaf proanthocyanidins: from agricultural production by-products to potential bioactive molecules.

Proanthocyanidins (PAs) are a class of polymers composed of flavan-3-ol units that have a variety of bioactivities, and could be applied as natural biologics in food, pharmaceuticals, and cosmetics. PAs are widely found in fruit and vegetables (F&Vegs) and are generally extracted from their flesh and peel. To reduce the cost of extraction and increase the number of commercially viable sources of PAs, it is possible to exploit the by-products of plants.

Advances in green solvents for production of polysaccharide-based packaging films: Insights of ionic liquids and deep eutectic solvents.

The problems with plastic materials and the good film-forming properties of polysaccharides motivated research in the development of polysaccharide-based films. In the last 5 years, there has been an explosion of publications on using green solvents, including ionic liquids (ILs), and deep eutectic solvents (DESs) as candidates to substitute the conventional solvents/plasticizers for preparations of desired polysaccharide-based films. This review summarizes related properties and recovery of ILs and DESs, a series of green preparation strategies (including pretreatment solvents/reaction media, ILs/DESs as components, extraction solvents of bioactive compounds added into films), and inherent properties of polysaccharide-based films with/without ILs and DESs.

Fruit variability impacts puree quality: Assessment on individually processed apples using the visible and near infrared spectroscopy.

This study was designed to have the absolute definition of 'one apple to one puree', which gave a first insight into the impacts of fruit inter-variability (between varieties) and intra-variability (between individual fruits) on the quality of processed purees. Both the inter-variability of apple varieties and the intra-variability of single apples induced intensive changes of appearance, chemical and textural properties of their corresponding microwave-cooked purees. The intra-variability of cooked purees was different according to apple cultivars.

Experimental and theoretical investigation on interactions between xylose-containing hemicelluloses and procyanidins.

During processing of plant-based foods, cell wall polysaccharides and polyphenols, such as procyanidins, interact extensively, thereby affecting their physicochemical properties along with their potential health effects. Although hemicelluloses are second only to pectins in affinity for procyanidins in cell walls, a detailed study of their interactions lacks. We investigated the interactions between representative xylose-containing water-soluble hemicelluloses and procyanidins.

Reactivity of flavanols: Their fate in physical food processing and recent advances in their analysis by depolymerization.

Flavanols, a subgroup of polyphenols, are secondary metabolites with antioxidant properties naturally produced in various plants (e.g., green tea, cocoa, grapes, and apples); they are a major polyphenol class in human foods and beverages, and have recognized effect on maintaining human health.

Revisiting the contribution of ATR-FTIR spectroscopy to characterize plant cell wall polysaccharides.

The contribution of ATR-FTIR spectroscopy to study cell wall polysaccharides (CWPs) was carefully investigated. The region 1800-800 cm was exploited using principal component analysis and hierarchical clustering on a large range of different powders of CWPs based on their precise chemical characterization. Relevant wavenumbers were highlighted for each CWP: 1035 cm was attributed to xylose-containing hemicelluloses, 1065 and 807 cm to mannose-containing hemicelluloses, 988 cm to cellulose, 1740 and 1600 cm to homogalacturonans according to the degree of methylation.

Mid-infrared technique to forecast cooked puree properties from raw apples: A potential strategy towards sustainability and precision processing.

The potential of MIRS was investigated to: i) differentiate cooked purees issued from different apples and process conditions, and ii) predict the puree quality characteristics from the spectra of homogenized raw apples. Partial least squares (PLS) regression was tested both, on the real spectra of cooked purees and their reconstructed spectra calculated from the spectra of homogenized raw apples by direct standardization. The cooked purees were well-classified according to apple thinning practices and cold storage durations, and to different heating and grinding conditions.

Interactions between cell wall polysaccharides and polyphenols: Effect of molecular internal structure.

Cell wall polysaccharides (CPSs) and polyphenols are major constituents of the dietary fiber complex in plant-based foods. Their digestion (by gut microbiota) and bioefficacy depend not only on their structure and quantity, but also on their intermolecular interactions. The composition and structure of these compounds vary with their dietary source (i.

Changes in cell wall neutral sugar composition related to pectinolytic enzyme activities and intra-flesh textural property during ripening of ten apricot clones.

The changes of texture and cell wall characteristics of apricot were investigated in ten clones at two maturity stages. Fruit firmness, cell wall composition and enzyme activity of three apricot flesh zones were analysed. The AIS (alcohol-insoluble solids) were characterised by high amounts of uronic acid (179-300 mg g AIS) and relatively high amounts of cellulosic glucose (118-214 mg g AIS).

Multiscale Localization of Procyanidins in Ripe and Overripe Perry Pears by Light and Transmission Electron Microscopy.

Histochemical staining with 4-dimethylaminocinnamaldehyde (DMACA), light microscopy, and transmission electron microscopy (TEM) were applied to characterize procyanidin localization at ripe and overripe stages in perry pear flesh (cv. 'De Cloche'). Pear flesh contained stone cell clusters surrounded by very large parenchyma cells.

Fresh, freeze-dried or cell wall samples: Which is the most appropriate to determine chemical, structural and rheological variations during apple processing using ATR-FTIR spectroscopy?

Attenuated total reflectance Fourier transform spectroscopy (ATR-FTIR) was applied on fresh (NF), freeze-dried (FD) and cell wall materials (AIS) of raw and processed apples. These samples prepared from 36 apple sets and the corresponding 72 purees, issued from different varieties, agricultural practices, storage periods and processing conditions, were used to build models including exploratory analysis, supervised classification and multivariate calibration. Fresh and freeze-dried samples presented similar fingerprint spectral variations due to processing.

Impact of onions in tomato-based sauces on isomerization and bioaccessibility of colorless carotenes: phytoene and phytofluene.

Onions as an interesting ingredient have been proved to promote Z-isomerization of lycopene and increase bioaccessibility of total-lycopene. Phytoene (PT) and phytofluene (PTF), the precursors of lycopene, are colorless carotenes, which are attracting much attention and are also abundant in tomatoes. Therefore, onions might also affect the distribution and bioaccessibility of PT and PTF isomers during heating tomato (hot-break and cold-break purees)-onion-extra virgin olive oil (EVOO) sauces.

Interactions of arabinan-rich pectic polysaccharides with polyphenols.

Given the high prevalence of arabinan side chains in pectic polysaccharides, this work aims to unveil the impact of their structural diversity on pectic polysaccharides-polyphenol interactions. To assess the effect of arabinan branching degree, sugar beet arabinans (branched and debranched) were used and compared to the well-known structure of apple arabinan and other pectic polysaccharides. Furthermore, arabinans contribution to pectic polysaccharides/polyphenol interactions was assessed.

A new application of NIR spectroscopy to describe and predict purees quality from the non-destructive apple measurements.

The potential of NIRS was investigated on both apples and purees to (i) examine factors involving quality variability (variety, agricultural practice, cold storage, puree mechanical refining level) and (ii) establish the link between quality traits before and after processing in order to predict the quality characteristics of purees from spectral information of raw apples. Apples and purees were well-classified at over 82% and 88% according to varieties and storage times respectively. The PLS models showed a good ability to estimate puree characteristics from spectra acquired on corresponding apples such as viscosity (R > 0.

Heating tomato puree in the presence of lipids and onion: The impact of onion on lycopene isomerization.

Z-lycopene isomers are more bioavailable than all-E-lycopene, especially 5-Z-lycopene. Based on our observations, the addition of unblanched onion could favor Z-isomerization of lycopene (by more than 94%) during heating tomato-onion-extra virgin olive oil (EVOO) purees at 90 °C for 2 h. The increase in Z-lycopene was correlated linearly with the addition of unblanched onion, with R > 0.

Impact of air-drying on polyphenol extractability from apple pomace.

Little data are available on the impact of pomace pre-treatment, notably drying, on the nature and yield of polyphenols. Pomace from two apple varieties ('Avrolles' and 'Kermerrien'), pressed with and without oxidation, were air-dried to different degrees. Drying led to the loss of native molecules, notably 5-O-caffeoylquinic acid and flavan-3-ols.

A D-optimal mixture design of tomato-based sauce formulations: effects of onion and EVOO on lycopene isomerization and bioaccessibility.

A D-optimal mixture design was used to study the effects of onion and extra virgin olive oil (EVOO) on lycopene Z-isomerization, lycopene diffusion into oil (expressed as a partition factor between tomato-based puree and oil) and in vitro bioaccessibility of lycopene isomers after thermal treatment of tomato-based puree consisting of tomato (75-100%), onion (0-20%) and EVOO (0-5%). A decrease of tomato puree could improve lycopene Z-isomerization, lycopene diffusion and lycopene bioaccessibility. The component interactions had an important influence on the Z-isomerization of lycopene, besides the linear mixtures of components.

Revisiting the chemistry of apple pomace polyphenols.

Hot water is an easily implementable process for polyphenols extraction. To evaluate the effect of this process on apple pomace, the overall polyphenolic composition was assessed before and after hot water extraction, followed by extractions with aqueous/organic solutions. As determined by UHPLC-DAD, flavan-3-ols were the main apple native polyphenols.

Procyanidin-Cell Wall Interactions within Apple Matrices Decrease the Metabolization of Procyanidins by the Human Gut Microbiota and the Anti-Inflammatory Effect of the Resulting Microbial Metabolome In Vitro.

B-type oligomeric procyanidins in apples constitute an important source of polyphenols in the human diet. Their role in health is not known, although it is suggested that they generate beneficial bioactive compounds upon metabolization by the gut microbiota. During apple processing, procyanidins interact with cell-wall polysaccharides and form stable complexes.

ATR-FTIR spectroscopy to determine cell wall composition: Application on a large diversity of fruits and vegetables.

Infrared spectroscopy coupled with multivariate analyses such as linear regressions was applied to assess the main cell wall components of a huge diversity of fruits and vegetables belonging to 29 plant species. The methodology was tested on the raw freeze-dried powders and on their corresponding AIS (Alcohol Insoluble Solids) dried by solvent exchanges. The most informative spectral region was 1750-1035 cm.

Pear ripeness and tissue type impact procyanidin-cell wall interactions.

Procyanidins and cell walls were extracted from pear at ripe and overripe stages in order to investigate the impact of ripening stage on their association. Procyanidin composition and structure remained stable at the overripe stage. Mid Infrared Spectroscopy (MIR) discriminated cell wall-procyanidin complex from initial purified cell wall material (CWM).