Chemistry - Sodium Bisulfate vs Sodium Bisulfite
Solution 1:
- Sodium bisulphate (NaHSO4): an acid
- Sodium bisulphiTe (NaHSO3): an antioxidant
- Sodium metabisulphiTe (Na2S2O5): another antioxidant
In short, bisulphate and bisulphite are not interchangeable, but bisulphite and metabisulphite are.
Sodium metabisulphite is prepared from sodium bisulphite via dehydration, as in this equation: $$\ce{2 NaHSO3 -> Na2S2O5 + H2O }$$ It's reversible in aqueous solution. The assumption that 30 mg of metabisulphite contain the same amount of sulphite as 30 mg of bisulphite is OK, the error is small, about 10 %. The correct amount would be 27 mg of metabisulphite.
You'd ask yourself if pasteurization (75 deg. C, 30 seconds) would work to deactivate the polyphenoloxidase without affecting flavour too much.
I'd also suggest searching Pubmed (it's a decent alternative to commercial citation databases) for such keywords as "polyphenol oxidase" (that's the enzyme that causes browning), "inhibition" and "sulfite".
If you want hands-on answers I'd suggest going to the library and get (via interlibrary loan) a copy of this paper: Plant Foods Hum Nutr. 1995, 47, 245-56, "The control of polyphenol oxidase activity in fruits and vegetables. A study of the interactions between the chemical compounds used and heat treatment."
From the abstract: ... Interactions between the use of ascorbic acid, citric acid, EDTA, sodium metabisulphite and heat treatment (70 degrees C for 2 min) in the control of PPO activity were studied in avocado ..., banana ..., apple ..., pear ..., peach ..., potato ..., eggplant ..., mushroom ... and hearts-of-palm ... . The results demonstrated that PPO of avocado and eggplant was most resistant to inhibition by the methods used. ... The results indicated that, with the exception of PPO from avocado, the most adequate alternative method to substitute for the use of SO2 in the control of PPO was a combination of ascorbic acid, citric acid and heat treatment.
This shows that how to get on top of browning while still having a presentable product is a tough problem and an active area of research. Also, avocado seems a specially hard case.
Solution 2:
Generally, sodium hydrogen sulfite and sodium hydrogen sulfate are not interchangeable.
Sodium hydrogen sulfite or “sodium bisulfite” (NaHSO3) is used in food processing as sanitising agent for food containers and fermentation equipment, preservative to reduce or prevent microbial spoilage, selective inhibitor of undesirable microorganisms in the fermentation industries, and as an antioxidant and inhibitor of enzyme-catalysed oxidative discoloration and non-enzymic browning. The food additive code (the E number, which is commonly found on food labels) of sodium hydrogen sulfite is E 222.
Sodium hydrogen sulfate or “sodium bisulfate” (NaHSO4) is used as acidity regulator. The food additive code of sodium hydrogen sulfate is E 514.
Solution 3:
Sulfate will not provide the antioxidant effect you seek. Metabisulfite has antioxidant effect.