*3.5.1 Light roast*

**3.4 Storage**

*Coffee - Production and Research*

**68**

reduced the quality of the product [54].

**3.5 Roasting, grinding, and drewing**

Right after the coffee beans are graded, they have to be kept in a storage house until they shipped and sold in the market. The temperature and relative humidity of the storehouse should be controlled to maintain the coffee quality without losing its intrinsic sensorial characteristics and physical and chemical properties and to store for a longer time. Afonso [55] reported that as the storage relative humidity is higher for an extended time, it decreases the compositions of reducing sugars in green coffee beans. Several research reports are available about the effects of storage conditions on the sensorial quality of coffee beans. He also mentioned that the 60% relative humidity with longer storage causes to cellular degradation and leads to oil leaking, which also contributes to the chemical compositions of green coffee beans. When the storage duration is prolonged, the oil becomes more acidic, and it

The most critical factor in the coffee value chain is roasting, where the physicochemical changes lead to the fulfilment of the roasted coffee characteristics [55]. Roasting is considered the essential steps in the formation of the aroma and flavour properties [56]. The essential reactions during coffee roasting and which are responsible for the colour, volatile compounds, and flavour developments are called Maillard reaction and caramelization. Minerals are vital catalysts in the various biochemical reactions responsible for the formation of different aroma and flavour compounds [57]. Amino acids have an important role in the formation of nitrogen/ sulphur heterocyclic compounds called melanoidins during roasting because of Maillard reaction or caramelization, which are considered as crucial compounds for flavour development [58]. When the roasting temperatures are higher than 200°C, the precursors in green coffee are transformed into roasted coffee constituents, which lead to the development of diverse aroma test and colour [59]. However, the coffee's intrinsic quality is predetermined in the green bean by its precursor composition, and the roaster only can unlock the full potential by applying the appropriate and optimised roasting conditions. Optimising the appropriate roasting conditions is undoubtedly the most critical ways for achieving the desirable coffee aroma [60]. Fobe and his co-workers [61] reported that as the roasting time is extended, the following changes occurred: the sugar content is reduced and then raised; caffeine contents showed insignificant changes; protein continuously decreased; free fatty acid improved; and unsaponifiable compounds declined. Another report mentioned that the lipid and organic acid increased, while the trigonelline and caffeine content showed almost unchanged [60]. During roasting net losses of matters in the form of water vapour, CO2, and volatile compounds are exhibited. The roasting duration and the final temperature of the coffee beans determine the development of flavour compounds [62]. A different flavour profile may occur because of the time–temperature and roasting conditions, even though the same coffee beans and roaster are used [63]. The physical properties and kinetics of aroma development of coffee showed differences as the coffee is roasted for a shorter time at high temperature compared to beans roasted for a longer time at low temperature [64, 65]. Fast roasting generates more soluble solids and causes less degradations of CGA, and the loss of volatile was lower [66]. However, the fast roasted coffee is considered affected by lipid oxidation because of high migration of oil from the inner part of the coffee beans to the surface [1]. The determining factors of the final coffee quality are roasting profile, roasting degree, and the

The lightly roasted coffee developed light brown colour, and it is preferred to make a coffee with a mild body. It has light fragrant, floral or fruity coffee notes. In this roasting condition, the coffee beans should not develop oil on their surface. It is also characterised with pronounced acidity and high caffeine content. During light roasting, the internal temperature of the coffee bean reached approximately 204°C (**Figure 5A**).
