**Background:** Galactosemia is a genetic disorder caused by deficiency of enzymes (GALK, GALE, GALT) involved in galactose metabolism, leading to accumulation of galactose and potentially fatal complications such as cataracts, mental retardation, and liver damage if untreated. In Korea, the birth frequency is approximately 1 in 40,000. Lifelong dietary restriction of galactose is essential, but available galactose content data are limited to 276 US foods from before 2000, which do not reflect Korean foods or cooking methods. Existing HPLC methods with RI or ELS detectors have low sensitivity (LOD 5–20 mg/100 g), making them inadequate for detecting trace galactose. This study aimed to analyze galactose and other sugars in 107 Korean agricultural products using a more sensitive GC/FID method with TMSO derivatization.
**Methods:** A total of 107 samples were selected based on Korean consumption data and requests from patients and clinicians, including 17 cereals, 7 potatoes/starches, 11 beans, 5 mushrooms, 16 vegetables, 25 fruits, 17 meats/eggs, and 9 seafoods. Samples were freeze-dried, pulverized, extracted with 60% ethanol, and deproteinized with lead acetate. TMSO derivatization was performed using hydroxylamine hydrochloride, HMDS, and TFA. GC/FID analysis used an Agilent 7890A system with an HP-5 column (30 m × 0.25 mm × 0.25 μm), injection temperature 280°C, detector temperature 300°C, and a temperature gradient program. Six sugars (fructose, galactose, glucose, sucrose, lactose, maltose) were quantified. Calibration curves were prepared at 0.1–20 mg/100 g. LOD and LOQ were calculated from blank noise. All samples were analyzed in duplicate.
**Key Results:** The GC/FID method separated all six sugars within 30 minutes, with retention times of 14.566 min (fructose), 16.203 min (galactose), 16.699 min (glucose), 26.978 min (sucrose), 28.602 min (lactose), and 29.563 min (maltose). Calibration curves showed excellent linearity (R² ≥ 0.9986 for all sugars). LOD for galactose was 0.3445 mg/100 g, and LOQ was 1.0439 mg/100 g, far lower than HPLC methods (5–20 mg/100 g). Galactose content varied widely across food groups: Cereals: 0–12.63 mg/100 g (highest in sirutteock, 12.63 mg/100 g; not detected in non-glutinous rice and glutinous rice). Potatoes: 0–36.01 mg/100 g (garnet sweet potato steamed, 36.01 mg/100 g; Japanese sweet potato steamed, 12.75 mg/100 g; starches had no detectable galactose). Beans/nuts/seeds: 0–58.34 mg/100 g (red bean paste, 58.34 mg/100 g; boiled chestnut, 16.79 mg/100 g; boiled red bean, 0.16 mg/100 g). Mushrooms: 0.08–3.54 mg/100 g (matsutake grilled, 3.54 mg/100 g). Vegetables: 0–61.56 mg/100 g (Kabocha squash steamed, 61.56 mg/100 g; iceberg lettuce, 29.08 mg/100 g; blanched zucchini, 23.09 mg/100 g; perilla leaf, 10.48 mg/100 g). Fruits: 0–132.09 mg/100 g (dried persimmon, 132.09 mg/100 g; kiwifruit, 21.05 mg/100 g; blueberry, 13.43 mg/100 g; sweet persimmon, 13.41 mg/100 g; avocado, 10.05 mg/100 g). Meats/eggs: 0–8.48 mg/100 g (egg yolk fried hard-boiled, 8.48 mg/100 g; chicken breast grilled, not detected). Seafood: 0–5.71 mg/100 g (abalone boiled, 5.71 mg/100 g; stir-fried anchovy, not detected).
**Clinical Implications:** This study provides the first comprehensive galactose content database for 107 Korean agricultural products using a highly sensitive GC/FID method. Foods with very high galactose content (e.g., dried persimmon 132.09 mg/100 g, Kabocha squash 61.56 mg/100 g, red bean paste 58.34 mg/100 g, garnet sweet potato 36.01 mg/100 g) should be strictly avoided by galactosemia patients. Foods with moderate content (e.g., avocado 10.05 mg/100 g, blueberry 13.43 mg/100 g, kiwifruit 21.05 mg/100 g) require careful portion control. Safe foods include most mushrooms, meats, and seafood (all <10 mg/100 g), as well as non-glutinous rice and glutinous rice (not detected). The data also highlight that cooking methods matter: wet cooking can reduce galactose content by leaching into water, but may reduce palatability. This database fills a critical gap for Korean patients who previously relied on outdated US data. However, processed foods remain unanalyzed and pose risks. The GC/FID method's superior sensitivity (LOD 0.3445 mg/100 g) enables detection of trace galactose, supporting more precise dietary management and potentially reducing complications from inadvertent galactose intake.