Sulfites

SULFITES:

I DO NOT use sulfites in any of my products!



I thoroughly dry (gently) my fruits and vegetables, so sulfites are not needed.



However, sulfites are more prevalent than you might think... very commonly added to wines, but also to dried fruit: especially apricots, "golden" raisins, and mangos, which lose their nice bright color without sulfites.





If you've been getting headaches or rashes, you might want to assess if you're consuming a lot of sulfites!





Getting technical/food science:



Purpose of Sulfite additives: inhibit spoilage by unwanted yeasts, molds, and bacteria, as well as color preservation.

 

1. Do Sulfites Inhibit Yeasts from Fermenting?

General Effect

Sulfites can inhibit yeast activity, but the extent depends on the yeast strain, sulfite concentration, and timing of application.

Mechanism

Sulfur dioxide (SO₂) disrupts yeast metabolism by interfering with enzymes involved in fermentation, such as glyceraldehyde-3-phosphate dehydrogenase, which is critical for energy production. It also affects cell membrane integrity.

Winemaking Context

Selective Inhibition

In winemaking, sulfites are often added to grape must to suppress wild (non-Saccharomyces) yeasts and other microbes, allowing cultured Saccharomyces cerevisiae (a sulfite-tolerant yeast) to dominate fermentation. Typical levels for this purpose are 50–100 ppm, which inhibit wild yeasts without significantly affecting commercial strains.

Concentration Matters

At low to moderate levels (20–50 ppm), sulfites may slow yeast activity but not stop it. Higher levels (above 100 ppm) can delay or inhibit fermentation, especially for sensitive strains. Winemakers often wait 24–48 hours after sulfite addition for levels to drop before adding yeast.

Sulfite-Tolerant Yeasts

Some yeast strains, like Saccharomyces cerevisiae, are naturally more resistant to sulfites, while others (e.g., Brettanomyces) are more sensitive. This is why sulfites are effective in controlling spoilage yeasts post-fermentation.

Practical Outcome

Sulfites don't typically prevent fermentation when used at standard levels in winemaking (up to 150 ppm for white wines, 100 ppm for reds). However, excessive sulfites can delay or stall fermentation, requiring careful management.

2. Do Sulfites Inhibit Molds?

General Effect

Yes, sulfites are effective at inhibiting mold growth.

Mechanism

Sulfites disrupt fungal cell processes by penetrating cell membranes (especially in acidic environments) and interfering with metabolic enzymes. They also create an unfavorable environment by reducing available oxygen, which molds need to grow.

Applications

  • In dried fruits and vegetables (e.g., apricots, sun-dried tomatoes), sulfites (500–3,000 ppm) prevent mold growth by inhibiting spore germination and mycelial development.
  • In winemaking, sulfites protect grape must from mold contamination during harvest and processing.

Effectiveness

Molds are generally more sensitive to sulfites than yeasts. Levels as low as 10–50 ppm can inhibit mold growth, though higher concentrations are used in practice for longer-term preservation.

Limitations

Sulfites are less effective against established mold colonies and may not eliminate all mold spores, especially in high-moisture environments.

3. Do Sulfites Inhibit Bacteria?

General Effect

Yes, sulfites are highly effective against many bacteria, particularly spoilage bacteria.

Mechanism

Sulfites disrupt bacterial metabolism by inhibiting enzymes, damaging cell membranes, and reducing intracellular pH. They are most effective in acidic environments (pH < 4), where free sulfur dioxide (the active form) is more prevalent.

Specific Bacteria

Lactic Acid Bacteria (LAB)

Sulfites inhibit bacteria like Lactobacillus and Pediococcus, which can cause off-flavors in wine (e.g., malolactic fermentation is sometimes intentionally delayed with sulfites).

Acetic Acid Bacteria

Sulfites are particularly effective against Acetobacter, which can turn wine into vinegar by producing acetic acid.

Other Spoilage Bacteria

Sulfites control a wide range of bacteria in food and beverages, including those causing spoilage in dried fruits and vegetables.

Concentration

Levels of 20–50 ppm can inhibit most bacteria, with 50–100 ppm commonly used in winemaking to ensure bacterial control without affecting yeast fermentation.

Limitations

Some bacteria, like certain strains of Bacillus or sulfate-reducing bacteria, may be more resistant to sulfites, requiring higher concentrations or additional preservatives.

Key Considerations

pH Dependency

Sulfites are most effective in acidic environments (e.g., pH 3–4, common in wine and dried fruits), where free SO₂ is active. In neutral or high-pH environments, their antimicrobial efficacy decreases.

Concentration and Timing

Low levels (10–50 ppm) selectively inhibit sensitive microbes (wild yeasts, molds, bacteria) while allowing fermentation by tolerant yeasts. Higher levels (100–3,000 ppm, as in dried fruits) provide broader antimicrobial action but may affect flavor or fermentation if misapplied.

Regulatory Limits

In the U.S., sulfite levels are capped at 350 ppm for wine and up to 2,000–3,000 ppm for dried fruits (depending on the product and region). Labels must declare sulfites above 10 ppm.

Sulfite Sensitivity

For sulfite-sensitive individuals, high-sulfite foods like dried apricots (up to 150 mg per 50g serving) pose a greater risk than wine (10–30 mg per glass).

 

Sulfite Health Effects & Concentration in Foods

Here's a list in descending order of sulfite levels in common foods. (Note: I don't add sulfites! Nice! I carefully dehydrate and thin slice everything so sulfites are not needed.) Check labels for "sodium sulfite", "sodium metabisulfite", or "sulfur dioxide "

Allergic Reactions

  • Skin Reactions: Sulfites can trigger hives (urticaria), itching, or flushing in sensitive individuals. These are often immune-mediated responses.
  • Anaphylaxis: In rare cases, sulfites may cause severe allergic reactions, including anaphylaxis, especially in those with a history of allergies. Symptoms include swelling, difficulty swallowing, or rapid heart rate.

Gastrointestinal Symptoms

Nausea, vomiting, abdominal pain, or diarrhea can occur, particularly with high sulfite intake (e.g., from wine or dried fruits). These symptoms may result from irritation of the gut lining or hypersensitivity reactions.

Headaches and Migraines

Some individuals report headaches or migraines after consuming sulfite-containing foods or beverages, particularly wine. The exact mechanism is unclear but may involve vascular or neurological sensitivity.

Neurological Effects (Rare)

In cases of sulfite oxidase deficiency (a rare genetic disorder), unmetabolized sulfites can accumulate, potentially causing neurological symptoms like seizures, developmental delays, or brain damage. This is extremely rare and not typically associated with dietary sulfites in healthy individuals.

Cardiovascular Symptoms

In sensitive individuals, sulfites may cause low blood pressure, rapid heartbeat, or dizziness, often as part of an allergic or anaphylactic response.

Fatigue or Weakness

Some report feelings of fatigue, weakness, or malaise after sulfite exposure, possibly due to systemic inflammation or hypersensitivity reactions.

Key Points

  • Sulfite Sensitivity: Affects about 1% of the general population, with higher prevalence (up to 10%) in asthmatics. Most reactions are not true allergies but hypersensitivity responses.
  • Severity and Variability: Symptoms vary widely, from mild discomfort to severe reactions, depending on individual sensitivity, sulfite dose, and metabolism efficiency.
  • High-Risk Foods: Common sources include wine, dried fruits, processed foods, and certain seafoods, where sulfites are used as preservatives.

Management

  • Avoiding sulfite-containing foods is key for sensitive individuals. Check labels for additives like sodium sulfite, sodium metabisulfite, or sulfur dioxide (often listed as E220–E228 in Europe).
  • Regulatory agencies like the FDA mandate labeling for sulfites above 10 ppm in foods due to potential health risks.

Rank Food Item Typical Serving Size Estimated Sulfites (mg per serving) Notes/Source
1 Dried Apricots 40g (6–8 pieces) 80–200 Up to 3000 mg/kg permitted (FSANZ); assumes high-end concentration.
2 Dried Mango 40g (1/4 cup) 60–120 Up to 3000 mg/kg; similar to dried fruits.
3 White Wine 150mL (1 glass) 10–30 Mean 122 mg/L; assumes high-end for sweet wines.
4 Red Wine 150mL (1 glass) 7–20 Mean 70 mg/L; lower than white wine.
5 Grape Juice (Concentrate) 240mL (1 cup) 5–20 Up to 2000 mg/kg in concentrates, diluted in serving.
6 Maraschino Cherries 10g (2 cherries) 5–15 Up to 1000 mg/kg; high due to preservation.
7 Dried Potatoes 50g (1/2 cup) 5–15 Up to 500 mg/kg; used to prevent browning.
8 Sausages (Processed) 100g (2 links) 5–15 Up to 450 mg/kg in some regions (FSANZ).
9 Shrimp (Frozen) 100g (3–4 oz) 5–10 Up to 100 mg/kg; used to prevent black spots.
10 Pickled Vegetables 50g (1/4 cup) 2–10 Up to 450 mg/kg; varies by product.
11 Fruit Jam 20g (1 tbsp) 1–5 Up to 1000 mg/kg; small serving size.
12 Molasses 20g (1 tbsp) 1–5 Up to 1000 mg/kg; used in processing.
13 Canned Vegetables 130g (1/2 cup) 1–5 Up to 450 mg/kg; varies by vegetable.
14 Lemon Juice (Bottled) 15mL (1 tbsp) 0.5–3 Up to 200 mg/kg; small serving size.
15 Soup Mix (Dry) 30g (1/4 packet) 0.5–3 Up to 500 mg/kg; varies by brand.
16 Hard Cider 355mL (12 oz) 0.5–3 Up to 200 mg/L; similar to wine.
17 Potato Chips 30g (1 oz) 0.5–2 Up to 500 mg/kg; low per serving.
18 Baked Goods (e.g., Bread) 50g (1 slice) 0.5–2 Up to 200 mg/kg; used in dough conditioning.
19 Trail Mix 40g (1/4 cup) 0.5–2 Contains dried fruits; varies by mix.
20 Guacamole (Processed) 30g (2 tbsp) 0.3–1 Up to 100 mg/kg; small serving size.

Notes

  • Sulfite Content: Expressed as sulfur dioxide (SO₂) equivalents, as per regulatory standards. Levels are estimates based on maximum permitted concentrations (e.g., FSANZ, GSFA) and typical serving sizes.
  • Variability: Actual sulfite levels depend on processing, brand, and regional regulations. Always check product labels for sulfite declarations (>10 ppm requires labeling in most countries).
  • Sources: Data derived from web references, including FSANZ, FDA, and EFSA guidelines.
  • Sensitivity: Individuals with sulfite sensitivity should avoid foods with high sulfite levels (>100 ppm) and consult a dietitian for personalized advice.

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.