Antoni Femenia

Compositional features of polysaccharides from Aloe vera (Aloe barbadensis Miller) plant tissues

A complete chemical characterisation of Aloe vera plant (Aloe barbadensis Miller) was carried out from the dissection of the plant whole leaves in filets and skin. In addition, a mucilaginous gel extracted from the filets was also characterised. Extraction with ethanol of lyophilised Aloe fractions (AIRs) allowed to concentrate the major fraction composed of carbohydrates up to 80%. The composition of the main type of polysaccharides present in the Aloe AIRs was determined. Mannose and cellulosic glucose were the major polysaccharide components in all AIRs, significant amounts of pectic polysaccharides were also detected. Sequential extraction of polysaccharides present in Aloe vera plant portions, revealed that two main types of mannose-containing polymers were present in the Aloe vera plant. The polysaccharide detected in the filet and in the gel fractions corresponded to a storage polysaccharide located within the protoplast of the parenchymatous cells. Its structural and compositional features corresponded to the active polysaccharide known as acemannan. On the contrary, in the skin tissue, the mannosyl residues arose from a structural polysaccharide located within the cell wall matrix. Structural and compositional differences between both polymers were confirmed by methylation analysis. The fact that acemannan is a reserve polysaccharide might help to explain most of the compositional variations reported in the literature for Aloe vera carbohydrates. Further, sequential extraction allowed us to identify several pectic polysaccharides, rich in uronic acids, with a composition similar to that of several antitumoral polymers found in different plant tissues.

Effects of addition of carrot dietary fibre on the ripening process of a dry fermented sausage (sobrassada).

Four formulations of a dry fermented sausage, known as sobrassada, containing different percentages of carrot dietary fibre (DF) [3% (S3), 6% (S6), 9% (S9) and 12% (S12) (w/w)] were analyzed for various physico-chemical and microbiological parameters and sensory attributes. The ripening process was monitored throughout storage. The pH of DF-supplemented sobrassadas was critically affected during ripening by the amount of DF incorporated, the values for sobrassada samples containing over 3% of DF suggested that the fermentation process in these samples was not successful. In addition, textural parameters, such as hardness and compression work, were significantly affected by the addition of over 3% of DF. The lipolytic process, one of the major biochemical events, was only affected when relatively large percentages of DF concentrate were incorporated. Thus, S3 and S6 samples exhibited similar free fatty acid profiles to the control throughout ripening.

Cauliflower (Brassica oleracea L), globe artichoke (Cynara scolymus) and chicory witloof (Cichorium intybus) processing by‐products as sources of dietary fibre

By-products arising from vegetable processing activities have been assessed in relation to their potential application as sources of dietary fibre supplements in refined foods. Sources used were fresh cauliflower, globe artichoke and chicory witloof. Non-starch polysaccharide (NSP) content and composition of selected parts of each plant source have been measured from alcohol insoluble residues (AIR) and by fibre analysis, complemented by methylation analysis to characterise structural features of component polysaccharides. Results indicate that cauliflower upper stem NSP was similar to the floret (∽25 g kg−1 fresh weight) and each was rich in pectic polysaccharides. Cauliflower lower stem was enriched in NSP (∽66 g kg−1) due mainly to cellulose and xylan deposition, which resulted in a proportionate decrease in pectic polysaccharides. Artichoke stem (∽38 g NSP kg−1) was similar to the receptacle (∽34 g NSP kg−1) but bracts were heavily lignified. Chicory root and leaf bud were each rich in pectic polysaccharides but NSP content was much higher in the root (∽46 g kg−1) than the leaf (∽8 g kg−1). Results indicate that processing by-products, eg cauliflower upper stem, artichoke stem and chicory root, could prove useful as sources of pectic polysaccharide-rich supplements. However, polysaccharide composition and glycosidic linkage pattern also identified important structural differences between sources. The importance of ‘fibre type’ when considering development of food supplements is discussed.

Proanthocyanidin composition and antioxidant potential of the stem winemaking byproducts from 10 different grape varieties (Vitis vinifera L.).

Stem byproducts from 10 different grape (Vitis vinifera L.) varieties were evaluated in terms of their total phenolic and total proanthocyanidin contents, flavan-3-ol and proanthocyanidin profiles, and antioxidant capacity measured by ABTS, CUPRAC, FRAP, and ORAC assays, with a view to the recovery of their natural bioactive compounds. Stems from Callet, Syrah, Premsal Blanc, Parellada, and Manto Negro varieties yielded the highest total phenolic and total proanthocyanidin contents and showed the greatest antioxidant capacities, whereas Chardonnay and Merlot stems presented the lowest values. Varieties differed significantly (p<0.05) with regard to both the phenolic composition and antioxidant capacity of their stems. However, no significant differences (p>0.05) were observed when stems from red and white varieties were considered separately. For the 10 grape varieties investigated, this is the first study presenting a detailed description of their stem flavan-3-ol composition determined by HPLC-UV-fluo. All of the analyses confirmed the stem byproducts as a potential polyphenol-rich source, especially promising in the case of the Callet variety.

Effect of rehydration temperature on the cell wall components of broccoli (Brassica oleracea L. Var. italica) plant tissues

Broccoli florets and stems tissues were rehydrated at different temperatures, namely 25°C, 40°C, 55°C, 65°C and 80°C. Water sorption capacity (WSC) values exhibited by broccoli tissues largely depended on the temperature used. Broccoli tissues showed maximum WSC values when rehydration was performed at relatively low temperatures. A significant correlation was found between WSC and the total arabinose content of broccoli tissues. Further, sequential extraction of pectic polymers revealed that samples with lower WSC exhibited a larger solubilisation of neutral pectic side-chains, the florets sample being rehydrated at 40°C which better maintained the original pectin structure. Overall, the results suggest that arabinose-rich pectin neutral side-chains might play an important role on the water sorption process of dehydrated broccoli tissues.

Developmental and ripening-related effects on the cell wall of apricot (Prunus armeniaca) fruit

Alcohol-insoluble residues (AIRs) were prepared from apricots at six stages during development/ripening on the tree. To investigate the changes in cell wall polymers, and in particular those affecting pectic polysaccharides, the AIR preparations were sequentially extracted with water, cyclohexane-trans-1,2-diamine-N,N,N′,N′-tetraacetate (CDTA) and Na2CO3. A significant proportion of initially Na2CO3-soluble pectic polysaccharides became water- and CDTA-soluble during the ripening process. In terms of composition, a significant decrease in galactose and uronic acid content was detected in all the extractions, whereas the percentage of arabinose increased in both water and CDTA-soluble polymers but decreased in the Na2CO3-extracted polysaccharides. The ability of pectic polysaccharides to cross-link was diminished during ripening due to an overall increase in the concentration of Na+ or K+ associated with the AIRs. This was accompanied by a decrease in the amounts of Ca2+ and Mg2+. The decrease in pectic galactans and the inhibition of pectin cross-linking detected within the pectic backbone are probably linked to the softening process observed during apricot ripening.

Simulation of the drying curves of a meat-based product: effect of the external resistance to mass transfer

Abstract A simple mathematical model solved by the separation of variables method is proposed to simulate the drying curves of a meat-based product (sobrassada), taking into account the influence of the external mass transfer resistance. By using the experimental data of a drying curve obtained at 14 °C and 85% relative humidity (RH), both effective diffusivity and external mass transfer coefficients were simultaneously identified (2.86×10 −11 m 2 /s and 3.99×10 −3 m/s, respectively). The proposed model allowed the accurate simulation of the drying curves of this meat-based product at different RHs (from 70% to 85% RH) (average %var=99.8%) and even when samples had a different chemical composition (%var=98.1%) to that used to carry out the parametric identification.

Characterization of Polyphenols and Antioxidant Potential of White Grape Pomace Byproducts (Vitis vinifera L.)

A detailed assessment of the total phenolic and total tannin contents, the monomeric and oligomeric flavan-3-ol composition, the proanthocyanidin profile, and the antioxidant potential of the grape pomace byproducts (considered as a whole, both skins and seeds), derived from four white grape varieties (Vitis vinifera L.), was performed. Significant differences (p < 0.05) of the total phenolic content, total tannin content, and antioxidant capacity of grape pomace byproducts were observed among the different grape varieties studied. For the first time in the literature, the particular flavan-3-ol composition of the four grape varieties investigated was described for the whole fraction of their grape pomace byproducts. The phenolic composition and antioxidant capacity of grape pomaces were compared to those of their corresponding stems. The global characterization of these white grape varieties provided a basis for an integrated exploitation of both winemaking byproducts as potential, inexpensive, and easily available sources of bioactive compounds for the pharmaceutical, cosmetic, and food industries.

The use of ultrasound velocity measurement to evaluate the textural properties of sobrassada from Mallorca

Abstract The usefulness of ultrasonic velocity measurements as a non-destructive technique to evaluate the moisture content and textural properties of sobrassada de Mallorca (a raw cured pork product) was assessed. Moisture content, ultrasonic velocity and textural properties were periodically measured in samples of sobrassada during ripening at 15°C and 75% RH. From the results obtained, two periods of ripening could be clearly distinguished, a first period (0–40 days of ripening) and a second period (40 to the end of the ripening), under the experimental conditions used in this study. The ultrasonic velocity could be mathematically related with the moisture content and textural parameters such as hardness, compression work, maximum puncture force and puncture work during the first period of ripening. In the second period, some physical modifications were inferred to occur which could be detected through the textural parameters, the ultrasonic velocity and by using optical microscopy. Overall, these results showed the ultrasonic techniques could be used to accurately estimate the moisture content and the textural parameters of sobrassada during the first period and also as a reliable method to detect changes in textural properties after prolonged ripening.

Tissue-related changes in methyl-esterification of pectic polysaccharides in cauliflower (Brassica oleracea L. var. botrytis) stems

Abstract. Pectic substances are a major component of cell walls in vegetable plants and have an important influence on plant food texture. Cauliflower (Brassica oleracea L. var. botrytis) stem sections at different regions of the mature plant stem have been monitored for tissue-related changes in the native pectic polysaccharides. Chemical analysis detected appreciable differences in the degree of methyl-esterification (ME) of pectic polysaccharides. About 65% of galacturonic acid (GalpA) residues were methyl-esterified in floret tissues. Relative ME showed a basipetal decrease, from 94% in the upper stem to 51% in the lower-stem vascular tissues. The decrease was not related to a basipetal increase in glucuronic acid (GlcpA) residues. The monoclonal antibodies, JIM 5 and JIM 7, produced distinct labelling patterns for the relatively low-methyl-esterified and high-methyl-esterified pectin epitopes, respectively. Labelling was related to cell type and tissue location in the stem. Floret cell walls contained epitopes for both JIM 5 and JIM 7 throughout the wall. Stem vascular tissues labelled more strongly with JIM 5. Whereas pith parenchyma in the upper stem labelled more strongly with JIM 7, in the lower-stem pith parenchyma, JIM 5 labelling predominated. Localization of pectic polysaccharide epitopes in cell walls provides an insight into how structural modifications might relate to the textural and nutritional properties of cell walls.