Laboratory simulations of the transformation of peas as a result of heat treatment: changes of the physical and chemical properties

Abstract

The residues of heated organic remains, usually called carbonized or charred remains, are ubiquitous in the archaeological record and are often used to interpret certain aspects of past ways of living. This study focuses on the physical and chemical alterations, both as a function of temperature and time that occur when the transformation of a polysaccharide-rich biomass is simulated in the laboratory. Peas (Pisum sativum) are heated at temperatures ranging from 130-700 (C under anoxic conditions and atmospheric pressure, during a maximum of 2 h. Changes in weight and the relative percentages of C, N, H and O are noted alongside modifications of the internal and external morphology. Vitrinite reflectance provides an elegant tool to determine the heating temperature of the residues. The kinetics that determine the changes and modifications are discussed. The resulting solid products of the heating process can be conveniently considered in five phases, which fit the physical and chemical properties. The simulation provides a rigorous basis for the study of the formation processes, as applied in the archaeology, after the so-called "carbonization" process.

Laboratory simulations of the transformation of emmer wheat as a result of heating

“…2) in the range of T oven =220 up to 250°C is the result of dehydration, which is confirmed by the clear liquid in the outlet tube (Table 2). This liquid was not further analysed, but most likely only water is released at these temperatures and pressures [14,15]. The C content rises strongly from 220 up to 250°C, indicating that relatively less C containing compounds were removed from the residues in this temperature range.…”

“…One grain of AR was heated in a pre-heated oven to determine the thermal regime inside the grains [15]. The temperature, as a function of the time, inside and outside the grain was measured using thermocouples.…”

Laboratory simulations of the transformation of peas as a result of heating: the change of the molecular composition by DTMS

“…The experiments were carried out under chemical ionization (CI) and low voltage ionization (EI) conditions. The changes as a result of heating of the internal and external morphology, the elemental composition and the vitrinite reflectance of the peas have been presented in an earlier study [4].…”

“…Because the terms carbonization and char are ill defined and have different meanings in the different fields of research [4], the process of heating has been defined as the product resulting from heat treatment: the solid residue.…”

Effects of amendment of different biochars on soil carbon mineralisation and sequestration

“…As shown in the literature, biochars made from wood have higher C/N values than those made from grass (Krull et al 2009). Higher pyrolysis temperatures result in lower volatile matter content and higher C/N ratio in biochar (Braadbaart et al 2004;Downie et al 2009;Krull et al 2009). …”