Sodium metabisulphite (SMBS) is used across genuinely different industries — from wine-making to water dechlorination to photography — and the grade you need depends entirely on what it's touching.
Food-Grade SMBS (E223)
Food-grade sodium metabisulphite, listed as the preservative E223, is used as an antimicrobial and antioxidant preservative in wine-making, dried fruit, and other food and beverage applications where a permitted sulphite preservative is called for. It carries the purity control and documentation needed for food-contact use.
See Sodium Metabisulphite (Food Grade) and the BASF Food Grade (E223) option.
Industrial / Non-Food Grade SMBS
Industrial-grade SMBS is the standard choice for dechlorination of treated water (a common step before discharge or reuse), as a reducing agent in various industrial processes, in photographic fixing solutions, and in textile bleaching/dyeing processes — anywhere the sulphite chemistry is needed but food-contact purity isn't required.
See Sodium Metabisulphite (SMBS) and the BASF Non-Food Grade option.
Why the Grade Distinction Matters
Even though the active compound is the same, food-grade product carries controls on heavy-metal and other impurity limits that industrial grade doesn't guarantee — never substitute industrial-grade SMBS into a food or beverage application. For water dechlorination, effluent treatment, or other non-food industrial use, the standard industrial grade is the appropriate and more economical choice.