1 Scope
This standard specifies determination method of inositol in foods for infants and young children, milk and milk products.
This standard is applicable to the determination of inositol in foods for infants and young children, milk and milk products.
2 Normative References
The documents referenced in this standard are indispensable for the application of this standard. For dated references, only the dated edition is applicable to this standard. For undated references, the latest edition (including all amendments) is applicable to this standard.
Method I Microbiological Method
3 Principle
Quantitation determination shall be carried out on the content of material to be tested in specimen by using the specificity and sensitivity of saccharomyces uvarum to inositol. In the culture medium with all the nutritional ingredients except the material to be tested, the growth of microorganisms and the content of the material to be tested are in linear relation; the content of materials to be tested in specimen may be worked out by comparing the light transmittance and the standard working curve.
4 Reagents and Materials
Unless otherwise specified, reagents used in this method are all analytically pure, and water is Grade 2 water specified in GB/T 6682.
4.1 Bacterial strain: saccharomyces uvarum, ATCC 9080.
4.2 Inositol standard: molecular formula C6H12O6, purity ≥%.
4.3 Sodium choloride (NaCl).
4.4 Sodium hydroxide (NaOH).
4.5 Culture medium
4.5.1 Malt extract agar culture medium: reference to Appendix A.
4.5.2 Culture medium for inositol determination: reference to Appendix A .
4.6 Sodium chloride solution (9g/L): weigh 9.0g sodium chloride, dissolve it in 1000mL water and put it into test tube respectively. There shall be 10mL in each test tube and sterilization shall be carried out at 121℃ for 15min.
4.7 Hydrochloric acid (1mol/L): weigh 82.0mL hydrochloric acid, dissolve it in water and scale the volume to 1000mL after cooling.
4.8 Hydrochloric acid (0.44mol/L): weight 36.6mL hydrochloric acid, dissolve it in water and scale the volume to 1000mL after cooling.
4.9 Sodium hydroxide solution (600g/L): weigh 300g sodium hydroxide, dissolve it in water and scale the volume to 500mL after cooling.
4.10 Sodium hydroxide solution (1mol/L): weigh 40 g sodium hydroxide, dissolve it in water and scale the volume to 1000mL after cooling.
4.11 Inositol standard solution
4.11.1 Inositol standard stock solution (0.2mg/mL): put inositol standard a dryer with phosphorus pentoxide for drying above 24h, weigh 50mg inositol standard (4.2) (accurate to 0.1mg), dissolve it fully with water, scale the volume to 250mL and store it up in refrigerator.
4.11.2 Inositol standard intermediate solution (10μg/mL): pipette 5mL inositol standard stock solution (4.11.1), scale the volume to 100mL with water and store it up in refrigerator.
4.11.3 Inositol standard working solution (1μg/mL and 2μg/m): pipette 10mL inositol standard intermediate solution (4.11.2) twice and scale the volume to 100mL and 50mL with water respectively. This working solution needs to be prepared before use every time.
4.12 Desiccant: phosphorus pentoxide (P2O5).
4.13 Glass bead：diameter is about 5mm.
