Japan Wax

Japan wax is sold as a wax but is a fat. Japan's food-additive standard defines it as the product obtained from the fruit of the wax tree Toxicodendron succedaneum (L.) Kuntze (Rhus succedanea L.) with glyceryl palmitate as its main constituent, so, like bayberry wax, it saponifies as a glyceride and carries a fatty-acid profile. Specification (JSFA 10th edition, MHLW 2024, monograph Mokuro / Japan Wax, also called Nihon-ro and haze fat; Japanese text): glossy white to faintly yellow lumps with a characteristic odour; melting point 48-54 C; saponification value 200-235; iodine value 5-30; purity: acid value not more than 30, lead not more than 2 ug/g, arsenic not more than 1.5 ug/g; residue on ignition not more than 0.3 %. The monograph names no melting-point method, and the standard's General Test 42 says measurement is by Method 1 unless otherwise specified: a closed capillary, the melting point being the temperature at which the sample has completely melted and become transparent, i.e. a clear point. Method 2, the open-capillary rising point meant for fats and waxes, applies only where a monograph names it, as Rice Bran Wax does (70-83 C, Method 2); Bees Wax, Carnauba Wax and Japan Wax name none. Fatty acids: Sano, Aikawa and Murase (1964) analysed a commercial refined, sun-bleached Japan wax from Nakagawa Seiro Co. (Yoshii, Fukuoka), nearly white, with melting point 53.4 C (method not stated, so not used), acid value 21.5, saponification value 220.0, iodine value (Wijs) 10.2 and unsaponifiable matter 1.3 %; the last three are recorded as the typicals beside the JSFA bands. They saponified 5.01 g, removed the unsaponifiables and recovered 4.50 g of acids, which n-hexane at 25-30 C split into a soluble mixed fatty acid fraction (4.14 g) and an insoluble brown solid (0.33 g, about 7.3 % of the ether extract) in which the dibasic acids were concentrated. Their Table 1, packed-column GLC (flame ionisation, 10 % PEGA; area %) of the mixed fatty acid fraction: C14:0 0.2, C15:0 0.2, C16:0 70.3, C16:1 1.1, C17:0 0.3, C18:0 13.0, C18:1 3.5, C20:0 7.6, C22:0 0.4, and unidentified peaks of 0.2, 1.0, 1.4 and 0.8; the authors put palmitic at about 70 % and palmitic, stearic, arachidic and oleic together at about 95 %. The recorded profile is therefore percent of the monobasic (hexane-soluble) acids, not of all acids, and it is one sample, so every value is a typical. Not mapped: C15:0 0.2 and C17:0 0.3 (odd-chain), the four unidentified peaks, and the dicarboxylic acids, which have no key. The hexane-insoluble fraction (Table 2, area %) was mainly C22 dicarboxylic (docosanedioic, 52.7) and C20 dicarboxylic (eicosanedioic, 34.0) acid, with smaller C8-C18 dicarboxylic acids and carried-over palmitic acid (7.9); dibasic acids from C5 to C22 were also found among the free acids. Tazaki (1971) measured the long-chain ones by GLC in the mixed fatty acids of raw, sun-bleached and refined Japan wax from Araki Seiro (Tagawa, Fukuoka): C20 dicarboxylic 2.34, 2.39 and 2.18 %, C22 dicarboxylic 2.16, 2.21 and 2.02 % (Table 4); the three waxes had acid values of 14.4, 21.4 and 20.9. Checks: the mapped acids sum to 96.1 %. As a triglyceride the profile implies a saponification value near 201; the measured 220.0 and the 200-235 band run higher, as expected for a fat carrying free acids (acid value 21.5 in this sample, up to 30 allowed) and two-carboxyl dicarboxylic acids. The 3.5 % oleic and 1.1 % palmitoleic account for an iodine value of only about 4 against the 10.2 measured on the same sample, so the 1964 packed column may have under-read the unsaturated acids or hidden some in the unidentified peaks; the oleic figure is more likely low than high. A related but different material, urushi wax from the fruit of the lacquer tree Toxicodendron vernicifluum, has its own monograph in the same standard (melting point 45-55 C, saponification value 200-235, iodine value 5-40, acid value not more than 50) and is not this record. Checked and not used: JP XVIII has no Japan Wax monograph (Japan wax appears only in the purity tests of its beeswax monographs), nor do the English 8th (FFCR) and 9th (NIHS) editions of the food-additive standard, where it is likewise only an adulterant test under Bees Wax; Tada et al. (Food Hyg. Saf. Sci. vol. 48, 2007) analysed Japan wax fatty acids by GC/MS but show them only as a chromatogram; the haze-wax cultivar surveys in Mokuzai Gakkaishi (Xu and Kawachi 1988; Tachibana et al. 1992), Tsujimoto (Bull. Chem. Soc. Jpn. 1935) and Schuette (J. Am. Oil Chem. Soc. 1942) are closed access and could not be opened. No source used prints an INCI name; CosIng's entry is Rhus Succedanea Fruit Wax ('a wax obtained from the mesocarp of the fruit of Rhus succedanea'), under the plant's older name, with CAS 8001-39-6 and no EC number.

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