Partitioning and in vitro bioaccessibility of apple polyphenols during mechanical and physiological extraction: A hierarchical clustering analysis with LC-ESI-QTOF-MS/MS.

Polyphenol partitioning during mechanical (cold-pressing) and physiological (digestion) extraction at the individual polyphenol and subclass level was investigated. UHPLC-ESI-QTOF-MS/MS analysis yielded a comprehensive identification of 45 polyphenols whose semi-quantification revealed a hierarchical clustering strongly determined by polyphenol structure and their location within the apple tissue. For instance, pomace retained most flavonols and flavanols (degree of polymerization DP 5-7), which were highly hydrophobic, hydroxylated, or large (>434 Da), and more abundant in peel. In vitro digestion UHPLC-ESI-QTOF-MS/MS analysis of whole apple (and its corresponding matrix-free extract) clustered polyphenols into five main groups according to their interaction with plant cell walls (PCWs) during each digestion phase. This grouping was not reproduced in pomace, which exhibited a greater matrix effect than whole apple during oral and gastric digestion. Nevertheless, the interaction between most polyphenol groups, including dihydrochalcones, flavanols (DP 1-4) and hydroxycinnamic acid derivatives, and pomace PCWs was lost during intestinal digestion.

Exploring novel organocatalytic-acetylated pea starch blends in the development of hot-pressed bioplastics.

Acetylated starch shows enhanced thermal stability and moisture resistance, but its compatibilization with other more hydrophilic polysaccharides remains poor or unknown. In this study, the feasibility of thermomechanically compounding organocatalytically acetylated pea starch (APS), produced at two different degrees of substitution with alkanoyl groups (DSacyl, 0.39 and 1.00), with native pea starch (NPS), high (HMP) and low methoxyl (LMP) citrus pectin, and sugar beet pectin (SBP, a naturally acetylated pectin) for developing hot-pressed bioplastics was studied. Generally, APS decreased hydrogen bonding (ATR-FTIR) and crystallinity (XRD) of NPS films at different levels, depending on its DSacyl. The poor compatibility between APS and NPS or HMP was confirmed by ATR-FTIR imaging. Contrariwise, APS with DSacyl 1 was effectively thermomechanically mixed with the acetylated SBP matrix, maintaining homogeneous distribution within it (ATR-FTIR imaging). APS (any DSacyl) significantly increased the visible/UV light opacity of NPS-based films and decreased their water vapor transmission rate (WVTR, by ca. 11 %) and surface water wettability (by ca. 3 times). In comparison to NPS-APS films, pectin-APS showed higher visible/UV light absorption, tensile strength (ca.2.9-4.4 vs ca.2.4 MPa), and Young's modulus (ca.96-116 vs ca.60-70 MPa), with SBP-APS presenting significantly lower water wettability than the rest of the films.

Systematic evaluation of the Folin-Ciocalteu and Fast Blue BB reactions during the analysis of total phenolics in legumes, nuts and plant seeds.

Folin-Ciocalteu and the more recent Fast Blue BB (FBBB) reactions are used for the quantification of total phenolics in food matrices. Despite its known interferences, Folin-Ciocalteu is still widely employed, considering Solid Phase Extraction (SPE) as clean-up step only in a few cases. Meanwhile, FBBB has shown no interferences for the determination of total phenolics in fruits and cereals, although its utilization in other popular matrices containing potential interferences, such as legumes, remains unexplored. In this study, the total phenolic content of 24 flours from legumes, cereals, fruits, nuts and plant seeds was evaluated by Folin-Ciocalteu and FBBB, with and without SPE. Folin-Ciocalteu showed interferences for 75% of the flours (attributed to reducing sugars and enediols), whereas FBBB only for legumes and nuts (attributed to the presence of tyrosine), both methods in those matrices requiring SPE. Although both SPE-FBBB and SPE-Folin-Ciocalteu presented excellent reproducibility, SPE-FBBB displayed 1.5 times higher sensitivity.

Fine structure, physicochemical and antioxidant properties of LM-pectins from okra pods dried under different techniques.

This work investigates the effect of drying okra pods by different techniques [freeze-drying (FD), sun-drying (SD), oven-drying (OD) and microwave-drying (MD)] on the molecular structure, physicochemical and antioxidant properties of the subsequently extracted OP. Remarkably, although the degree of methyl esterification (∼41.1 %) remained similar among samples, the content of galacturonic acid (62.67-68.77 %), average number molecular weight (MnI: 758.8-808.5 kDa, MnII: 20.9-24.2 kDa), and to a greater extent the apparent viscosity of an aqueous solution of pectin molecules, water holding capacity (0.21-10.71 g/g) and emulsifying activity (42.3-72.7 %) and stability (38.6-53.5 %), decreased with the drying temperature in the order of FD-OP > SD-OP > OD-OP > MD-OP. On the other hand, only FD-OP presented a higher proportion of galactan and/or arabinan side chains [(Ara + Gal) / Rha = 12.37%] compared to the rest of the samples, with values ranging from 7.79 to 9.17%. FD-OP and SD-OP resulted in lower DPPH and ABTS radical scavenging activities.

Long-term low shear-induced highly viscous waxy potato starch gel formed through intermolecular double helices.

We previously reported that waxy potato and corn starch amylopectin pastes undergo a shear-thickening behavior that occurs at a low shear rate range of 5 to 25 s-1, and that the effect did not occur for waxy rice starch. Here, we show that the same gelatinized potato amylopectin subjected to a prolonged shear rate of 20 s-1 for 24 h at 5 °C forms a highly viscous gel having a 4-fold higher number of double helices than without shear. Shear-induced starch retrograded aggregates began forming within 20 min of treatment. Amylopectin double helices melted between 40-75 °C resulting in a steep decrease in the storage modulus, indicating that gel formation was caused by intermolecular double helices. Thus, a new phenomenon is reported whereby a waxy potato amylopectin paste, in the presence of long-term low shear, forms double-helical aggregated structures that considerably affects the material's rheological properties.

Effect of oil and shortening in rice bread quality: Relationship between dough rheology and quality characteristics.

One of the main problems with gluten-free breads is their texture and their rapid staling. Fats are widely used for the improvement of texture and other quality parameters in gluten-free breads. The effect of oil and shortening in rice-breads quality and its correlation with dough rheology has been analyzed. The inclusion of oil increased the specific volume of the breads and reduced their hardness, particularly with lower levels of hydration, whereas shortening did not modify specific volume or reduced it when hydration levels were higher. Oil, at levels of up to 30%, reduced the cohesiveness, springiness and resilience of breads, as well as the brightness of the crust, and increased the a* and b* values. Breads with oil also exhibited a greater number of pores per cm2 , especially in doughs with higher levels of hydration. An inverse correlation between G' and G'' and bread specific volume has been observed, being the reciprocal-Y model a better predictor than the linear model to relate the bread specific volume. PRACTICAL APPLICATIONS: This study showed that the type and quantity of fat added in rice based breads affect the bread quality in a different way. In general, it can be said that the incorporation of up to 20% oil improved rice based breads. Oil increased the specific volume, the a* and b* parameters of the crust and the cell density. It also decreases hardness, cohesiveness, springiness, resilience, and the L* parameter. Converse to breads made with oil, the addition of shortening can negatively affect the quality of the breads. Moreover, the correlation analysis has demonstrated that the study of dough rheology could be a good predictor of gluten-free bread quality.

Changes in physicochemical properties and in vitro starch digestion of native and extruded maize flours subjected to branching enzyme and maltogenic α-amylase treatment.

Extrusion is an increasingly used type of processing which combined with enzymatic action could open extended possibilities for obtaining clean label modified flours. In this study, native and extruded maize flours were modified using branching enzyme (B) and a combination of branching enzyme and maltogenic α-amylase (BMA) in order to modulate their hydrolysis properties. The microstructure, pasting properties, in vitro starch hydrolysis and resistant starch content of the flours were investigated. Whereas BMA treatment led to greater number of holes on the granule surface in native samples, B and BMA extruded samples showed rougher surfaces with cavities. A reduction in the retrogradation trend was observed for B and BMA native flours, in opposition to the flat pasting profile of their extruded counterparts. The glucose release increased gradually for native flours as the time of reaction did, whereas for extruded flours a fast increase of glucose release was observed during the first minutes of reaction, and kept till the end, indicating a greater accessibility to their porous structure. These results suggested that, in enzymatically treated extruded samples, changes produced at larger hierarchical levels in their starch structure could have masked a slowdown in the starch digestion properties.