## 4 Comprehensive Review
### A Comprehensive Overview of Bioactive Compounds in Different Food Drying Systems
#### 4.1.6 Infrared
Studies indicate that, when properly applied, infrared radiation not only preserves but can even enhance antioxidant activity, particularly when drying times are minimized [108]. For instance, [PERSON] et al. [113] observed an increase in the anthocyanin content due to the breakdown of glycosidic bonds in complex anthocyanins, generating simpler and more bioactive forms. This is consistent with findings in other studies, where infrared drying positively impacted bioactive compounds such as flavonoids and anthocyanins. \begin{table}
\begin{tabular}{c c c c c} \hline
**No.** & **Drying Method** & **Material** & **Main Findings** & **Reference** \\ \hline \multirow{8}{*}{1} & & & The intermittent infrared drying method & \\  & & & ensured higher contents of phenolic & \\  & & & compounds and flavonoids & \\  & & & (423.67 mg/100 g and 6.08 mg rutin/100 & \\  & & & g dry matter, respectively). Although & \\  & & & citric acid decreased, its retention was & \\  & & & _platensis_ & better with continuous drying at 65 \({}^{\circ}\)C & \\  & & & and intermittent drying. Phycocyanin & \\  & & & content also declined but was better & \\  & & & & preserved under intermittent conditions & \\  & & & & (6.63 and 7.17 g/100 g dry matter). & \\  & & & & At 80 \({}^{\circ}\)C, infrared drying yielded similar & \\  & & & levels of total phenolics, flavonoids, and & carotenoids compared to convective drying: & \\  & & & & 189.70 \(\pm\) 5.87 mg GAE/100 g DM, & \\  & & & & 25.52 \(\pm\) 1.53 mg CE/100 g DM, and & \\  & & & & 32.20 \(\pm\) 0.92 g/g DM, respectively. & \\  & & & Antioxidant activity showed no significant & \\  & & & & difference (DPPH: & \\  & & & & 366.57 \(\pm\) 21.31 \(\mathrm{\SIUnitSymbolMicro m}\) TE/100 g DM; ORAC: & \\  & & & 4622.00 \(\pm\) 523 \(\mathrm{\SIUnitSymbolMicro m}\) TE/100 g DM). & \\ \hline \end{tabular}
\end{table} 
Table 8: Applications of infrared drying in food matrices. On the other hand, excessive exposure may lead to the thermal degradation of these compounds, resulting in a reduced antioxidant capacity. Some studies have shown that elevated temperatures caused by infrared radiation can negatively affect certain compounds, such as anthocyanins, which are particularly sensitive to oxygen and heat [103]. The combination of high temperatures and oxygen may decrease the content of these substances, highlighting the importance of strict temperature control to preserve bioactive compounds that require more specific conditions. Infrared drying also stands out for its energy efficiency. Since the radiation directly heats the water within the food, without needing to heat the surrounding air, the energy  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No. ** & **Drying Method** & **Material** & **Main Findings** & **Reference** \\ \hline
3 & Freeze-drying, hot air drying, infrared + hot air, relative humidity control drying, and pulsed vacuum drying & Fresh garlic (_Allium_ & Infrared combined with hot air was the fastest drying method (3.8 \(\pm\) 0.3 h) and resulted in the highest antioxidant activity (20.94 \(\pm\) 0.11 mg/mL), total phenolics (1.89 \(\pm\) 0.04 mg GAE/g), and allicin content (144.27 \(\pm\) 1.06 mg/100 g). Samples treated with freeze-drying & [107] \\
4 & Freeze-drying + near-IR after 20\% weight loss, freeze-drying + far-IR after 20\% weight loss, firezeze-drying + far-IR after 20\% weight loss & Acai  
consumption is significantly reduced. This results in a faster and more efficient drying process [111]. Additionally, shorter drying times imply less heat loss and lower electricity consumption, making this process an attractive option for industrial applications [112]. Despite these promising results, [PERSON] et al. [43] reported that infrared radiation caused a decrease in the bioactive compound content of the microalga Spirulina platensis, similar to what occurs with conventional drying methods. The authors attributed this to the absence of cellulose in the microalga's cell wall, making it more heat-sensitive.