Inbreeding offers numerous advantages but also presents some problems for the genetic improvement of cassava (Manihot esculenta Crantz). One of the concerns is that inbreeding depression (ID) may be too drastic for (even partially) inbred materials to survive. A large experiment was conducted to quantify ID in cassava. S1 families from eight elite cultivars, each represented mostly by over 90 cloned genotypes, were produced and evaluated in a replicated trial at one location. The results from this evaluation allowed measurement of ID levels for key traits such as fresh root yield (63.9%), fresh foliage yield (37.9%), harvest index (26.5%), plant height (10.1%), and dry matter content in the roots (5.3%). Results also indicated (as expected) that ID, for a given trait, was not uniform among the eight families evaluated. For reasons provided in the article, the ID levels measured in this study may have been overestimated. Compared with the first experiences introducing inbreeding in temperate and tropical maize (Zea mays L.), we concluded that the use of homozygous progenitors in future cassava genetic enhancement is feasible. The average ID and frequency distributions within S1 families for different traits correlated well with the relative importance of nonadditive genetic effects controlling their inheritance as reported in the literature.
The quality of cocoa depends on both the origin of the cacao and the processing stages. The roasting process is critical because it develops the aroma and flavor, changing the beans' chemical composition significantly by chemical reactions induced by thermal energy. Aspects have been identified as the main differences between bulk cocoa and fine cocoa, the effect of time and temperature on the formation of the flavor and aroma, and the differences between conductive heating in an oven, convective with airflow, and steam flow. Thermal energy initially causes drying, then non-enzymatic browning chemical reactions (Maillard reaction, Strecker degradation, oxidation of lipids, and polyphenols), which produce volatile and non-volatile chemical compounds related to the flavor and aroma of cocoa roasted. This review identified that the effect of the heating rate on the physicochemical conversion of cocoa is still unknown, and the process has not been evaluated in inert atmospheres, which could drastically influence the avoidance of oxidation reactions. The effect of particle size on the performance of product quality is still unknown. A more in-depth explanation of energy, mass, and chemical kinetic transfer phenomena in roasting is needed to allow a deep understanding of the effect of process parameters. In order to achieve the above challenges, experimentation and modeling under kinetic control (small-scale) are proposed to allow the evaluation of the effects of the process parameters and the development of new roasting technologies in favor of product quality. Therefore, this work seeks to encourage scientists to work under a non-traditional scheme and generate new knowledge.
Despite roasting being the most crucial step in cocoa
manufacture,
its thermochemical effects on cocoa are not entirely understood. This
work aims to understand the kinetics and chemical composition of the
volatile compounds formed during roasting. The weight loss of two
sizes of cacao powder was evaluated in thermogravimetric analysis
(TGA) with five heating rates (10 to 180 °C min–1), using air and nitrogen as the carrier gas. A global Friedman isokinetic
model was used to obtain kinetic data from the TGA measurements. For
this, seven different stages were discriminated, and the kinetics
were determined for each stage separately. PTV−GC−MS
identified the gas phase, and SPME−GC−MS quantified
the volatile compounds trapped in the solid phase. At intermediate
temperatures (150 to 250 °C), aromatics (e.g., pyrazines, aldehydes,
ketones, phenols, and pyrroles) are formed and transferred to the
gas at higher temperatures for a prolonged time. Typical Maillard
and Strecker degradation reaction products in both gas and solid phases
were identified and used to set up a reaction network for cocoa roasting.
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