Cactus pears (Opuntia ficus-indica) are draught resistant plants originated in Mexico. Their flattened stem segments, called cladodes, have moisture, protein and fibre contents of 92, 1-2 and 4-6% respectively, and a pectin content in the range of 0.8-3.3% depending on the species. They also contain certain concentration of carotenoids which are of special interest because of their antioxidant activity. This work is aimed to identify and quantify the main carotenoids present in the stems and to evaluate the effect of thermal treatments on the antioxidant activity and concentration of carotenoids and phenolic compounds. The carotenoids -cryptoxanthin, -carotene and lutein were identified in the cladodes, the latter having the highest concentration. Thermal treatments increased the extractability of these pigments and the antioxidant activity was related to the carotenoids concentration. Total phenolic content decreased after the thermal treatments; however this result had little effect on the antioxidant activity. Mucilage present in the stems decreased the extractability of the carotenoids.

Biosolids are waste from wastewater treatment and have a high content of organic matter and nutrients. In this study, not conventional physicochemical and biological properties of biosolids produced during different seasons of the year were evaluated. These properties are not considered in environmental regulations; however, they are of agronomic interest as indicators of quality and functionality in soils. Also, molecular analysis by Fourier-transform infrared (FTIR) was conducted, enzymatic analysis using the APIZYM® system was performed and two indices of functional and microbial diversity were established. The results showed that the biosolids had a high content of total organic carbon, total nitrogen, P, and K. FTIR analyses showed that chemical composition of biosolids was similar during all year. The C and N of microbial biomass demonstrated presence of active microorganisms, as well as a uniformity in its richness and abundance of species that could present a positive synergy with soil microorganisms. The enzymatic activities showed that the biosolids contained an enzymatic machinery available to promote the mineralisation of the organic matter of biosolids and could even transcend into the soil. Finally, biological properties can be used as indicators of quality and functionality of biosolids before being used as an organic amendment, especially in agricultural soils.

Starches isolated from four ayocote bean varieties were modified by thermal treatment to determinate the effect of the treatment on the structural changes of ayocote bean starch. Scanning electron microscopy indicates that the starch granules have oval and round shapes, with heterogeneous sizes and fractures when the extraction method is used. The presence of new bands at 2850 and 1560 cm in the FT-IR spectra showed that the thermal treatment of ayocote beans induced an interaction between the protein or lipid and the amylose or amylopectin, while the sharpest band at 3400 cm indicated a dehydration process in the starch granule in addition to the presence of the band at 1260 cm, indicating the product of the retrogradation process. The thermal treatment reduced the crystallinity as well as short-range order. Raman spectroscopy revealed that acute changes occurred in the polysaccharide bonds after thermal treatment. This study showed that the thermal treatment affected the structural properties of ayocote bean starches, the interactions of the lipids and proteins with starch molecules and the retrogradation process of starch.

In this study, a partial purification and characterization of the lectins from two varieties of Phaseolus coccineus (black and purple ayocote bean) was carried out. A partial purification of the lectins was performed by affinity chromatography on fetuin-agarose. The lectins’ characterization showed that the hemagglutination activity was only inhibited by the fetuin and that the saccharides (mono-, di- and tri-saccharides) do not influence their hemagglutination capacity. A difference in the relative molecular weight between the two Phaseolus varieties was observed, 28.5 kDa for the black variety and 30.6 kDa for the purple variety. In the lectins of both Phaseolus varieties, ions were detected in their structure and influenced their hemagglutination activity, principally to the ion Ca+2; on the other hand, only the lectins of the purple variety of the Phaseolus, had a detectable ion, Cu+2. The lectins showed thermostability in the temperature range of 25 and 70 °C, on the other hand, in the pH range between 3 and 10, the lectins showed hemagglutination activity. According to the obtained results, the structural differences between the lectins obtained from both Phaseolus varieties influence their hemagglutination activity.