Food Preservation Safety: Proven Methods, Hidden Risks, And Modern Solutions, Part 2

Today, food safety is defined not only by freshness but also by the purity of the environment in which food is stored. Modern technologies allow control over every factor - from the gas composition in packaging to the microclimate and container materials.

However, these advances also increase the risk of hidden contamination: migration of plastics, release of metals, formation of oxidized compounds, and mycotoxins - invisible toxins produced by molds that can persist even after heat treatment.

The goal is no longer just to extend shelf life, but to preserve nutritional value while preventing toxic exposure. Storage has become a continuation of production - the final and most critical stage of food safety.

Modern Technologies and Potential Storage Issues

• Vacuum Sealing - removes oxygen and slows oxidation but does not replace refrigeration: anaerobic bacteria (including C. botulinum) may multiply if temperature control is lost.
• Modified Atmosphere Packaging (MAP) - replaces oxygen in packaging with nitrogen (N₂) or carbon dioxide (CO₂). It extends the shelf life of meat, fish, and vegetables, but if the seal is compromised, spoilage occurs rapidly.
• Ionizing Radiation - an industrial method for eliminating microbes without heating. Packaging must display the Radura symbol or the label irradiated product, though it is often hard to notice. Radiation processing destroys some antioxidants and promotes the formation of oxidized fat compounds.
• Pasteurization - gentle heating (60-80 °C) used for liquids such as milk, juices, and sauces. It reduces microbial load for 3-7 days but partially denatures proteins and lowers vitamin bioavailability.

These technologies extend food life but do not automatically make it safer - the cleanliness of materials and storage conditions remains the key factor.

Environmental and Chemical Safety of Storage

Homemade preserves are often viewed as “pure food,” yet in practice, contact materials and storage conditions frequently become the main sources of toxins - as much as factory packaging. Long-term storage itself leads to material migration: substances enter food that were never meant to be there in the first place.

Materials

Metal

• Iron, tin, and aluminum can release metal ions when in contact with acidic foods (vinegar, tomatoes, berries).
• Cheap tin cans often contain lead or cadmium, and their internal coatings are epoxy resins with BPA/BPS, which mimic hormone activity

Better to use: glass jars with metal lids and silicone seals, or stainless steel grade 304/316 without inner coating.

Plastic and Silicone

• Food-grade plastics (PET, PP, PE) are safe only at room temperature or in the refrigerator. When heated above 40 °C, they release phthalates and bisphenols that can disrupt endocrine balance.
• PVC and polycarbonate are the most toxic types of plastic - these are the main sources of bisphenol migration.
• Silicone is safe only when labeled food grade (LFGB or FDA approved). Cheap construction or decorative silicone releases formaldehyde and plasticizers when heated.

For hot or long-term storage: use glass, stainless steel, or certified food-grade silicone.

Glass, Ceramics, and Paper

• Ideal for long-term storage: they do not react with food or absorb odors.
• Avoid decorative ceramics with unknown glaze - they may contain lead or cadmium.
• Paper packaging is safe only when coated with natural wax or cellulose, without synthetic varnishes.

Storage Conditions

Temperature and Light

• Heat accelerates vitamin degradation and the migration of compounds from packaging into food.
• Ultraviolet light destroys fats, pigments, and antioxidants.
• Temperature fluctuations cause condensation - moisture activates the growth of microbes and mold.

Store in a cool, dark place, at a stable temperature of 8-18 °C, away from direct sunlight.

Moisture and Oxygen

• Humidity above 60 % promotes mold growth and fat oxidation.
• Air exposure in fatty foods accelerates rancidity.

Use desiccants (silica gel) and oxygen absorbers (O₂ absorbers), and check packaging integrity and seal quality.

Odors and Cross-Storage

• Fat and sugar easily absorb foreign odors.
• Do not store near spices, smoked foods, or products with volatile aromas.

Optimal solution: separate containers or tightly sealed glass jars.

Shelf Life

Even perfectly packed products are not meant to last forever: oxidation, vitamin loss, and migration of packaging substances occur over time.
Shelf life depends on the preservation method and microclimate stability - cool (8-18 °C), dry (humidity < 50 %), dark, and oxygen-limited conditions.

• Refrigeration (+2…+8 °C): 3-7 days for greens, berries, dairy, and ready meals; requires stable temperature and no condensation.
• Freezing (-18 °C): 6-12 months for vegetables, fruits, meat, fish, and broths; only in airtight packaging, without thawing.
• Flash Freezing (-30 °C and below): 12-18 months for berries, herbs, and semi-finished products; minimal vitamin loss.
• Drying and Dehydration: up to 1-2 years for fruits, vegetables, herbs, and mushrooms; store in a dry, dark place with desiccant.
• Freeze-Drying (Sublimation): up to 25 years in airtight packaging with oxygen absorber and light protection.
• Fermentation: 6-12 months for sauerkraut, kimchi, and pickles - only when kept cool and under brine.
• Pickling and Salting: 8-12 months at pH < 4.2, in sterilized jars and a dark place.
• Jams, Preserves, Syrups: up to 2 years in cool storage; after opening - no longer than 1 month.
• Canned Foods (Autoclaving): 2-5 years at ≤ 20 °C and out of light; discard if bulging appears.
• Smoked and Cured Products: 3-6 months in a dry, cool, well-ventilated place (≤ 15 °C).
• Products in Oil, Alcohol, or Syrup: 1-3 months, only refrigerated and in small batches.
• Nuts, Seeds, and Grains: 6-12 months when kept cool with a desiccant.
• Flour, Spices, Tea, Coffee: 6-9 months in a dark, dry place without air exposure.

Common Mistakes and Myths in Food Storage and Processing

“All canned foods are safe.”
No. Only those that have undergone autoclaving under pressure and at a temperature of at least 115 °C are truly safe. Home-canned vegetables or meat processed in a simple water bath are a potential source of botulism. Clostridium botulinum spores survive boiling at 100 °C and become active in anaerobic conditions. Complete safety is achieved only when heated to 115-121 °C under pressure. Lack of awareness of this fact has caused numerous cases of poisoning from traditional home canning methods.

“Vacuum sealing replaces refrigeration.”
No. Removing air slows oxidation but does not stop the growth of anaerobic bacteria.
Without cold or an acidic environment, a vacuum creates ideal conditions for botulinum spores.

“Fermentation just means adding salt.”
No. Salt regulates osmotic pressure, but fermentation depends on sugars.
If vegetables are too salty and contain no sugar, the process won’t start properly and may turn into decay. Stable fermentation requires a temperature of +20…+24 °C, time, and clean containers.

“Drying is always safe.”
No. Plastic dehydrators release phthalates and bisphenols when heated. At temperatures above 60 °C, vitamins and enzymes are almost completely destroyed. Only stainless steel and moderate drying temperatures (up to 50 °C) are safe.

“Smoking is a natural preservation method.”
Only partly. Even “pure” smoking forms polycyclic aromatic hydrocarbons (PAHs) - carcinogenic compounds. “Liquid smoke” contains even more toxic phenols. Short cold-smoking and occasional consumption are much safer.

“Vinegar is the perfect preservative.”
Partially. It kills bacteria but, when consumed regularly, irritates mucous membranes and feeds Candida yeasts. Fermented vegetables (without vinegar) are gentler on the microbiome and provide a probiotic effect.

“Plastic packaging is universal.”
No. Plastic is safe only below 40 °C and without contact with fats. When heated, phthalates migrate into food. For hot or long-term storage, only glass or stainless steel should be used.

“Freezing preserves everything forever.”
Not quite. Ice crystals destroy tissue structure, and vitamins gradually degrade during long storage. Upon thawing, quality drops sharply. Do not store for more than 6 months and never refreeze.

“Salt and sugar are always safe.”
No. Excess salt raises blood pressure and burdens the kidneys; too much sugar promotes Candida growth and contributes to insulin resistance. Preservation should not become a source of metabolic stress.

“All BPA-free containers are safe.”
No. BPA is often replaced with BPS or BPF - chemicals that act as the same endocrine disruptors. Only glass and stainless steel without inner coatings are truly safe.

Mistakes in storage and processing rarely cause immediate harm but create a cumulative toxicological and microbiological risk. Mold, heavy metals, or botulinum toxin can contaminate food not because of “bad ingredients,” but due to a lack of understanding of the technology. A mindful approach means not fear of food preservation, but awareness: safety is about physics, microbiology, and cleanliness, not just “home methods.”

Practical Principles of Food Preservation

No method is perfect — each is a compromise between shelf life, nutritional value, and environmental impact.

• Freeze-drying and dehydration preserve the maximum amount of nutrients while reducing weight and extending storage life.
• Fermentation, salting, and dry-curing retain minerals and bioavailable vitamins but require stable temperature, cleanliness, and humidity control.
• Canning, pressure sterilization, and smoking ensure the longest shelf life but reduce nutritional quality and environmental purity.
• Freezing and flash-freezing maintain structure and flavor but depend entirely on consistent electricity supply.
• Oil, alcohol, and syrup preservation help retain aroma and taste but have limited shelf life and potential botulism risk.
• Pickling and sugar preservation (jams, marmalades) are reliable but associated with high acidity or sugar content.

Storage methods are chosen based on purpose and conditions:

• For short-term storage — cooling, vacuum sealing, and fermentation are suitable; they preserve taste and active substances without adding preservatives.
• For long-term storage — freeze-drying, dehydration, or canning of acidic foods are optimal; these methods provide maximum stability and minimal risk of microbial growth.
• For travel and storage without refrigeration — drying, salting, smoking, or their combinations are preferable; such foods are resistant to temperature fluctuations and retain energy value.

The best results are achieved by combining methods: fermentation followed by gentle drying preserves probiotics and flavor, while freeze-drying with vacuum sealing maintains structure and nutrients for years.

Mold and Mycotoxins: Hidden Risks of Food Storage

Fresh foods are always free from mold, but once storage begins, mold must be constantly kept in mind. Mold is part of the natural decomposition cycle - nature’s way of recycling organic matter back into the soil. In nature, it maintains balance; in stored foods, it becomes the enemy. When preserving food, we are not fighting nature - we are merely regulating its processes where they are premature. Maintaining optimal humidity, temperature, and ventilation is the only way to balance preservation and decay.

Mold (Aspergillus, Penicillium, Fusarium) is among the main sources of foodborne toxins, invisible to the eye and resistant to heat. Aflatoxins (A. flavus, A. parasiticus) are classified by the IARC as Group 1 carcinogens and damage the liver; ochratoxin A (A. ochraceus, P. verrucosum) is nephro- and neurotoxic; zearalenone and fumonisin (Fusarium) have estrogen-like effects and disrupt hormonal balance. These toxins are heat-stable, so cooking does not guarantee safety.

Drying and Dehydration

Main risk zone - nuts, grains, legumes, herbs, and fruits. Mold growth begins with poor air circulation or insufficient drying. Safe residual moisture: 8-10 %. Store in a dry place with humidity < 50 %, away from plastic and heat sources. Any musty smell or bitter taste - discard immediately.

Fermentation and Pickling

At temperatures above +25 °C and with air access, Mucor, Rhizopus, and Penicillium can develop. A thin white film can be removed; fuzzy growth or musty odor means the product should be discarded. Optimal fermentation range: +18…+22 °C; store finished products in the refrigerator.

Peanuts, Nuts, Grains, Spices, Coffee, Cocoa

Sources of contamination vary by product type:

• Peanuts - mature underground, where spores of A. flavus and A. parasiticus are naturally present. Infection occurs even before harvest in humid or poorly ventilated soil.
  Aflatoxins form inside the seeds and persist even after roasting. Peanuts and their products are the main source of aflatoxins in the human diet - even organic peanuts may contain them.
• Other nuts and grains (pistachios, almonds, walnuts, cashews, legumes, cereals) usually become contaminated during storage.
  Main toxins: aflatoxins, ochratoxins, and fusariotoxins (zearalenone, fumonisin, DON).
• Coffee - often contaminated by A. ochraceus and P. verrucosum during wet fermentation and storage in jute sacks; produces ochratoxin A, which is heat-resistant.
  Today, mold-tested “mycotoxin-free” coffee is commercially available.
• Cocoa, spices, and feed grains can contain mixed mycotoxins.
  When used in animal feed, some compounds convert into aflatoxin M₁, found in milk, meat, and eggs - allowing toxins to pass through the food chain to humans.

Store these foods in a dry, cool place (≤ 15 °C) in airtight glass or stainless-steel containers, away from moisture and light.

Canning and Marinades

Mold may develop on the brine surface if airtightness or acidity is compromised. A. niger and P. expansum survive in vinegar below 5 %. For safety, pH should be below 4.0, and jars must be sterilized thoroughly.

Smoking and Curing

White Penicillium nalgiovense is harmless and even protective, but when humidity exceeds 80 % or air stagnates, toxic A. candidus and Mucor racemosus may appear. Optimal conditions: ~75 % humidity, constant ventilation, no condensation or plastic contact.

Refrigerators, Cellars, and Basements

Main sources of spores - condensation and organic residues. Clean all storage surfaces monthly with vinegar or 3 % hydrogen peroxide, without harsh detergents or fragrances.

Processed Foods and Animal Feeds

Mycotoxins survive industrial processing, so trace amounts are present in coffee, cocoa, spices, dried fruits, nut butters, and cereal products. Particularly high risk exists in dry animal feeds, where mixtures of aflatoxins, ochratoxin, and fumonisin are often found. Animals accumulate toxins faster due to monotonous diets; for pets fed processed food, this risk is especially high.

Transmission of Mycotoxins Through the Food Chain

Aflatoxin B₁ in animals converts into aflatoxin M₁, which is secreted in milk and can accumulate in the liver and fat tissue. Ochratoxin A remains stable and accumulates in organs such as the liver and kidneys. Toxins from Fusarium affect animals differently - they disrupt hormonal and reproductive balance and can later affect humans as well.

Thus, contaminated feed becomes a continuous source of mycotoxins in human food. Monitoring aflatoxin and ochratoxin A in animal feed and raw materials is as essential as testing grains, coffee, or nuts for human consumption.

Conclusion

Modern storage technologies can extend food life for decades - yet they cannot override nature’s fundamental laws. Microbes, oxygen, moisture, and temperature still determine food safety and nutritional quality. From the choice of container material to ambient humidity, every step in the chain affects whether food becomes a source of health - or of toxins.

True safety is not achieved through sterilization or chemicals, but through attention to detail: clean containers, inert materials, stable microclimates, and reasonable storage times. A mindful approach is not a return to “grandmother’s methods,” but a synthesis of tradition and modern science - where technology serves nature, not replaces it, ensuring that food nourishes rather than harms.