Determination of the Major By-Products of Citrus hystrix Peel and Their Characteristics in the Context of Utilization in the Industry

Abstract

Kaffir lime (Citrus hystrix) is a popular citrus in Southeast Asia. Despite the growing interest in the peel of the fruit, the leaves are the most frequently used part of the fruit. The aim of the study was to determine the main by-products of the peel, such as pectins, minerals, essential oil, and bioactive compounds, and to evaluate the possibility of using them in various branches of industry. In the study of the essential oil obtained by hydrodistillation performed using the TGA chromatography technique (GC-MS), sabinene (31.93%), β-pinene (26%), and limonene (19%) were selected as the most abundant volatile compounds. Nine microelements (Fe, Zn, Cu, Mn, Co, Ni, Cr, Mo, and V), four macroelements (Mg, Ca, K, and Na), and seven ballast substances (Cd, Hg, Pb, Al, V, Sr, and Pt) were also determined using the microwave plasma-atomic emission spectrometry technique (MP-AES). In the case of microelements, iron 32.72 ± 0.39 mg/kg DW (dry weight) had the highest concentration. In the case of macroelements, the calcium content was 9416 ± 34 mg/kg DW. Optimization of the pectin extraction was also performed by selecting citric acid and obtaining a yield of 7.6–17.6% for acid extraction and 9.9–28.2% for ultrasound-assisted extraction (UAE), depending on the temperature used. The obtained pectins were characterized by the degree of methylation, galacturonic acid content, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, and DSC (differential scanning calorimetry) analysis. Among bioactive compounds, the contents of polyphenols (22.63 ± 2.12 mg GAE/g DW), flavonoids (2.72 ± 0.25 mg CE/g DW, vitamin C (2.43 ± 0.19 mg Asc), xantoproteins + carotenes (53.8 ± 4.24 ug), anthocyanins (24.8 ± 1.8 mg CGE/kg DW), and chlorophylls A and B (188.5 ± 8.1, 60.4 ± 3.23 µg/g DW) were evaluated. Antioxidant capacity using (cupric ion-reducing antioxidant capacity) CUPRAC and DPPH assays was also provided with the results of 76.98 ± 8.1, and 12.01 ± 1.02 µmol TE/g DW, respectively.

A comparative metabolomic investigation of different sections of Sicilian Citrus x limon (L.) Osbeck, characterization of bioactive metabolites, and evaluation of in vivo toxicity on zebrafish embryo

“…These results are in agreement with the study on Citrus x limon peels conducted by Mcharek, who reported 23.07 and 82.01 µM Trolox g −1 DW values for DPPH and ABTS, respectively (Mcharek & Hanchi, 2017). In addition, comparing these two cultivars with other species of the Citrus genus, it can be seen that their antioxidant potency is similar to that found in wild mandarin peel, with antioxidant activity ranging between 65.62–108.06 and 25.14–50.46 µM Trolox g −1 DM in the ABTS and DPPH assays, respectively (Zhang et al., 2014), but higher than the antioxidant capacity of kaffir lime peel (12.02 ± 1.02 µM Trolox g‐1 DW in DPPH assay) (Lubinska‐Szczygeł et al., 2023).…”

Characterization of Essential Oils from the Skin of <em>Citrus limetta</em> Risso, <em>Citrus limetta</em> Sp., <em>Citrus reticulata</em> and <em>Citrus sinensis</em> Grown in Northeastern Peru

“…Hydrodistillation is one of the most common methods for the extraction of essential oils and allows the use of environmentally friendly solvents [41]. As evidenced by results, citrus peels have different essential oil yields (0.43% for orange, followed by lime 0.35%, mandarin 0.18% and sweet lemon 0.15%), which is conditioned by the skin volume unlike citrus species that have thinner skin [42].…”

Evaluation of the physical and biological properties of chitosan film combined with Chúc (Citrus hystrix DC.) peel essential oil

“…Key components of this oil include β-pinene, sabinene, limonene, and citronellal. Furthermore, it has been shown to be safe for human use (Agouillal et al, 2017;Lubinska-Szczygeł et al, 2023). Given the outstanding advantages of Chúc oil, its application in food technology has great potential.…”