No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

a b s t r a c tThis study examined variables that influence the nitric acid-extraction of pectins from cacao pod husks. An initial screening study tested the main parameters influencing yield and uronic acid content by a factorial fractional 3 3−1 design. Additional studies used response surface methodology using a central composite design. Yield was optimized by increasing temperature. Uronic acid content was higher when pH is decreased and temperature is increased, or when pH is increased and temperature is decreased. To optimize both parameters, extraction conditions of pH 1.5 at 100 • C for 30 min provided a predicted yield and uronic acid content of approximately 9.5% and 80%, respectively. The obtained experimental value for the yield was 9.0 ± 0.4%, the pectin presenting 66.0% uronic acid. Chemical and spectroscopic analyses showed that this pectin is mainly a homogalacturonan highly esterified and acetylated (DE 56.6%; DA 17.1%) with some rhamnogalacturonan insertions.

Coffee plants were subjected to heat stress (37 °C) and compared with control plants (24 °C). Cell wall polysaccharides were extracted using water (W), EDTA (E) and 4M NaOH (H30 and H70). In addition, monolignols were analyzed, and the leaves were observed by microscopy. Plants under heat stress accumulated higher contents of arabinose and galactose in fraction W. Xylose contents were observed to decrease in H30 fractions after the heat stress, whereas galactose and uronic acid increased. H70 fractions from plants exposed to heat stress showed increased xylose contents, whereas the contents of arabinose and glucose decreased. Differences in the molar-mass profiles of polysaccharides were also observed. The primary monolignol contents increased after the heat stress. Structural alterations in palisade cells and ultrastructural damage in chloroplasts were also observed. Our results demonstrate that the chemical profile of coffee cell-wall polymers and structural cell anatomy change under heat stress.