Il Solfito di sodio è un composto chimico, sale disodico dell'acido solforoso.

E' etichettato come E221 nella lista degli additivi alimentari con funzione di conservante.

Migliora la capacità di impasto del pane.

Usato nella conservazione delle uova (1),

birra, caramello, prodotti da forno e insalate.

Ampiamente utilizzato nei vini.

Sebbene sia utilizzato come conservante generico, non è consentito nei prodotti a base di carne.

Dose giornaliera accettabile : 0,7 mg/kg peso corporeo

Può dare reazioni allergiche (2).

Cosmetica

E' un ingrediente soggetto a restrizioni come voce pertinente III/99 e V/9 negli allegati del regolamento europeo sui cosmetici n. 1223/2009. "The SCCNFP is of the opinion that inorganic sulfites and bisulfites do not pose a health risk when used in cosmetic products at concentrations up to 0.67% in oxidative hair dye products, up to 6.7 % in hair waving/straightening products, up to 0.45 % in self-tanning products for the face and up to 0.40 % in self-tanning products for the body (all expressed as SO2)" (3).

Agente antiossidante. Ingrediente che contrasta lo stress ossidativo e che evita danni cellulari. I radicali liberi, i processi infiammatori patologici, le specie reattive dell'azoto e le specie reattive dell'ossigeno sono responsabili del processo di invecchiamento e di molte malattie causate dall'ossidazione.

Agente ondulante e stirante per capelli. E' un ingrediente che consente la stiratura  e/o l'ondulazione modificando in modo permanente la forma o la configurazione delle fibre cheratinose dei capelli.

Conservante. Qualsiasi prodotto contenente composti organici, inorganici, acqua, ha necessità di essere preservato dalla contaminazione microbica. I conservanti agiscono contro lo sviluppo dei microrganismi dannosi e contro l'ossidazione del prodotto.

Agente riducente. Ingrediente che agevola l'ondulazione permanente dei capelli con un livello di pH ottimale.

Sicurezza

I sintomi riconducibili ad una sensibilità ai solfiti possono essere di varia natura e importanza. I più diffusi sono il mal di testa e prurito o gonfiore generalizzato, ma si sono verificati casi di nausea, broncocostrizione, diarrea, ipotensione, shock (4).

Il Gruppo di esperti scientifici dell'EFSA sugli additivi alimentari e gli aromatizzanti ha valutato il rischio per gli elementi tossici presenti nel biossido di zolfo-solfito (E 220-228), sulla base dei dati presentati dagli operatori economici interessati, e ha concluso che i limiti massimi delle specifiche UE per arsenico, piombo e mercurio dovrebbero essere abbassati e dovrebbe essere introdotto un limite massimo per il cadmio (5).

Solfito di sodio studi

Formula molecolare: Na₂O₃S   Na₂SO₃ 

Peso molecolare: 126.037 g/mol

UNII: VTK01UQK3G

CAS: 7757-83-7  68135-69-3

EC Number: 231-821-4

PubChem Substance ID 329824427

MDL number MFCD00003503

Sinonimi: 

• Sodium sulfite
• Disodium sulfite
• Sodium sulfite anhydrous
• Sulfurous acid, disodium salt
• Sulftech
• Natrium sulfurosum
• sodiumsulfite
• Natriumsulfid
• Natriumsulfit
• Natrii sulphis
• Anhydrous sodium sulfite
• E221
• CHEMBL1945334
• CHEBI:86477

Bibliografia_________________________________________

(1) Effects of sulfhydryl compounds, carbohydrates, organic acids, and sodium sulfite on the formation of lysinoalanine in preserved egg.
Luo XY, Tu YG, Zhao Y, Li JK, Wang JJ.  -  J Food Sci. 2014 Aug;79(8):T1621-8. doi: 10.1111/1750-3841.12543. 

(2) Contact allergy to sodium sulfite and its relationship to sodium metabisulfite.
Oliphant T, Mitra A, Wilkinson M.  -  Contact Dermatitis. 2012 Mar;66(3):128-30. doi: 10.1111/j.1600-0536.2011.02029.x.

(3)  0648/03 - Opinion concerning Inorganic Sulfites and Bisulfites

(4) Gunnison AF, Jacobsen DW. Sulfite hypersensitivity. A critical review. CRC Crit Rev Toxicol. 1987;17(3):185-214. doi: 10.3109/10408448709071208.

Abstract. Sulfiting agents (sulfur dioxide and the sodium and potassium salts of bisulfite, sulfite, and metabisulfite) are widely used as preservatives in foods, beverages, and pharmaceuticals. Within the past 5 years, there have been numerous reports of adverse reactions to sulfiting agents. This review presents a comprehensive compilation and discussion of reports describing reactions to ingested, inhaled, and parenterally administered sulfite. Sulfite hypersensitivity is usually, but not exclusively, found within the chronic asthmatic population. Although there is some disagreement on its prevalence, a number of studies have indicated that 5 to 10% of all chronic asthmatics are sulfite hypersensitive. This review also describes respiratory sulfur dioxide sensitivity which essentially all asthmatics experience. Possible mechanisms of sulfite hypersensitivity and sulfur dioxide sensitivity are discussed in detail. Sulfite metabolism and the role of sulfite oxidase in the detoxification of exogenous sulfite are reviewed in relationship to the etiology of sulfite hypersensitivity.

(5) EFSA Panel on Food Additives and Flavourings (FAF); Younes M, Aquilina G, Castle L, Engel KH, Fowler PJ, Frutos Fernandez MJ, Fürst P, Gundert-Remy U, Gürtler R, Husøy T, Manco M, Mennes W, Moldeus P, Passamonti S, Shah R, Waalkens-Berendsen I, Boon P, Cheyns K, Crebelli R, FitzGerald R, Lambré C, Mirat M, Ulbrich B, Vleminckx C, Mech A, Rincon AM, Tard A, Horvath Z, Wright M. Follow-up of the re-evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228). EFSA J. 2022 Nov 24;20(11):e07594. doi: 10.2903/j.efsa.2022.7594. 

Abstract. Sulfur dioxide-sulfites (E 220-228) were re-evaluated in 2016, resulting in the setting of a temporary ADI of 0.7 mg SO2 equivalents/kg bw per day. Following a European Commission call for data, the present follow-up opinion assesses data provided by interested business operators (IBOs) and additional evidence identified in the publicly available literature. No new biological or toxicological data addressing the data gaps described in the re-evaluation were submitted by IBOs. Taking into account data identified from the literature search, the Panel concluded that there was no substantial reduction in the uncertainties previously identified in the re-evaluation. Therefore, the Panel considered that the available toxicity database was inadequate to derive an ADI and withdrew the current temporary group acceptable daily intake (ADI). A margin of exposure (MOE) approach was considered appropriate to assess the risk for these food additives. A lower confidence limit of the benchmark dose of 38 mg SO2 equivalents/kg bw per day, which is lower than the previous reference point of 70 mg SO2 equivalents/kg bw per day, was estimated based on prolonged visual evoked potential latency. An assessment factor of 80 was applied for the assessment of the MoE. At the estimated dietary exposures, when using a refined exposure scenario (Data set D), MOEs at the maximum of 95th percentile ranges were below 80 for all population groups except for adolescents. The dietary exposures estimated using the maximum permitted levels would result in MOEs below 80 in all population groups at the maximum of the ranges of the mean, and for most of the population groups at both minimum and maximum of the ranges at the 95th percentile. The Panel concluded that this raises a safety concern for both dietary exposure scenarios. The Panel also performed a risk assessment for toxic elements present in sulfur dioxide-sulfites (E 220-228), based on data submitted by IBOs, and concluded that the maximum limits in the EU specifications for arsenic, lead and mercury should be lowered and a maximum limit for cadmium should be introduced.