Isomaltose

Twenty honey and two corn syrup samples were purchased from companies in China and Japan in 2017 (Table 1). Fructose and maltose were purchased from Nacalai Tesque (Kyoto, Japan). Glucose and sucrose were purchased from Fujifilm Wako Pure Chemical Industries (Osaka, Japan). Turanose, trehalose, and isomaltose were purchased from Tokyo Chemical Industry (Tokyo, Japan). Melezitose was purchased from Kanto Chemical (Tokyo, Japan).

Trehalose, fructose, succrose, maltose, glucose, arabinose, maltotriose isomaltotriose, xylose and were purchased from Tokyo Chemical Industry, TCI, (Europe, Belgium); ribose, raffinose, melibiose, gentiobiose, isomaltose and panose were obtained from Tokyo Chemical Industry, TCI, (Tokyo, Japan); iso-erythritol, galactitol, turanose, galactose, isomaltotriose, mannitol, rhamnose and sorbitol were purchased from Sigma-Aldrich (Steinheim, Germany); sodium hydroxide and sodium acetate trihydrate were from Merck (Darmstad, Germany). All aqueous solutions were prepared using ultrapure water (Thermofisher TKA MicroPure water purification system, 0.055 µS/cm). Standard solutions of glucose, fructose, and sucrose were prepared at 1000 ng/mL concentration, whereas 100 ng/mL was concentration of the rest of compounds. Calibration standards were prepared from the stock solutions by dilution with ultrapure water. The quality-control mixture used for monitoring instrument performance was prepared by diluting standards to concentrations in the range 0.9–100 ng/mL (depending on the concentration in samples).

The reagents used were of analytical grade and were purchased from FUJIFILM Wako Pure Chemicals or Nacalai Tesque unless otherwise noted. Kojibiose was purchased from Carbosynth, and isomaltose and β-glucose-1-phosphate were purchased from Tokyo Chemical Industries. Kojitriose, kojitetraose, kojipentaose, G2G6G, and G2G2G6G were synthesized by reverse phosphorolysis of Kojibiose phosphorylase (Caur_2019) from Chloroflexus aurantiacus J-10-fl (see Supporting information, Figs. S6 and S7). α-Glucans from L. citreum NRRL B-1299 and L. citreum NRRL B-1355 (35 , 36 , 37 (link)) were kindly provided by Dr Mikihiko Kobayashi. α-GlcF was prepared by deacetylation of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl fluoride (Merck Millipore).