SAFETY IN HOMEMADE FERMENTED FOODS

The relationship between nutrition and human health was first emphasized by Hippocrates with his famous saying, “Let food be thy medicine, and medicine be thy food.”

Today, due to the increasing prevalence of cardiovascular diseases, circulatory system disorders, and obesity-related conditions, consumers have been turning more toward functional foods and dietary supplements. In recent years, there has also been a growing interest in the consumption of traditional fermented foods.

Fermentation has been used for centuries as a method to extend the shelf life of foods and to enhance their nutritional quality. The word “fermentation” comes from the Latin term “fervere,” meaning “to boil.” Microorganisms break down carbohydrates and other macromolecules into simpler compounds, resulting in the production of various beneficial metabolites, including B vitamins, minerals, and Omega-3 fatty acids.

A wide variety of fermented products are produced both worldwide and in our country. Some examples include dairy (kefir, dried strained yoghurt), grains (boza, tarhana), meat (sucuk, pastirma), fish (fish sauce), soy (soy sauce, tempeh), as well as vegetables and fruits (kimchi, sauerkraut, sunki).

Fermented products are recognized for their antimicrobial, antioxidant, probiotic, prebiotic, cholesterol-lowering, functional, and therapeutic effects.

It has also been noted that fermented foods positively influence the human gut microbiota and various parts of the body, thereby supporting a healthy life and helping to protect against various diseases. In particular, the consumption of fermented foods containing live microorganisms has recently emerged as a key dietary strategy for enhancing human health. When examined in detail in terms of their content and health benefits, some of these products stand out as remarkable examples.

Hardaliye is a non-alcoholic, fermented Turkish beverage produced through lactic acid fermentation of red and black grapes, mustard seeds, and sour cherry leaves. Fermentation enhances both the aroma and texture while enriching the nutritional value of the food. Thanks to its antioxidant and phenolic content, Hardaliye reduces lipid peroxidation parameters and serum homocysteine concentrations. The resveratrol and flavonoids it contains have positive effects on the cardiovascular system, helping regulate blood pressure and blood sugar levels.

Kefir is a fermented dairy product produced by adding kefir grains to cow’s, sheep’s, goat’s, or mare’s milk, characterized by a mildly acidic and slightly sour taste. The main feature of kefir is that it is a probiotic itself and is more resistant to other probiotics. Kefir is rich in tryptophan, an amino acid, and contains high levels of calcium and potassium. It also contains vitamins B12, B1, biotin, and vitamin K. In addition to yeasts, kefir contains beneficial bacteria, including Bifidobacteria, Lactobacilli, Leuconostoc, Acetobacter, and Streptococcus. Kefir has anticarcinogenic, antiallergic, cholesterol-lowering, blood glucose-regulating, and antimicrobial properties, which can reduce lactose intolerance. Additionally, it has positive effects on blood pressure, the digestive system, and the immune system.

Tarhana is prepared by kneading yoghurt, wheat flour, bread yeast, spices (salt and red pepper), and vegetables (tomatoes and onions), and then leaving the mixture to ferment for a week. The resulting fresh tarhana dough, produced through the fermentation of yoghurt bacteria and yeasts, can be dried in the sun or in a dehydrator to make it storable. In addition to its prebiotic and probiotic content, tarhana is rich in vitamins and minerals. Its high fibre content helps regulate intestinal peristalsis and supports the digestive system.

Pickles made through lactic acid fermentation have health-protective effects. It has been reported that regular consumption of pickles is inversely associated with asthma, skin problems, and immune system-related diseases in children.

Kombucha tea is one of the most widely consumed non-alcoholic traditional fermented beverages in the world, obtained by fermenting sugar with acetic acid bacteria and yeasts. It is reported to support the digestive system and liver functions, enhance immunity, reduce the risk of obesity, and provide relief for patients with bronchitis and asthma. Kombucha also has positive effects against inflammation, edema, coronary and heart diseases, and stress-related health problems. In addition to all these benefits, it has been reported to possess anticancer, antimicrobial, and antioxidant properties.

Commercially produced fermented foods mostly serve as carriers for probiotic bacteria. However, despite growing interest in these foods and their potential public health benefits, significant confusion remains regarding which fermented foods actually contain live microorganisms and the extent to which these microorganisms affect the gut microbiome.

In traditional fermented foods, in addition to beneficial bacteria that contribute to fermentation, the growth of pathogenic and spoilage-causing bacteria must also be monitored.

Biogenic amines, particularly in protein-rich fermented foods, can form during fermentation and may serve as indicators of product freshness. However, biogenic amines formed in fermented foods can trigger allergic reactions, and excessive intake can lead to toxic effects. For example, in traditional cheeses, histamine is considered the most risky biogenic amine. Histamine can negatively impact product quality by altering taste, aroma, and texture. Preventing the formation of biogenic amines in cheese can be effectively achieved through improved hygiene and storage conditions, as well as the selection of appropriate starter cultures.

In homemade fermented vegetable products, such as pickles and kimchi, the changes that occur during fermentation serve as indicators of quality. For optimal fermentation, it is essential to prepare high-quality brine, use filtered water, select high-quality vegetables, and utilise suitable equipment. In a healthy fermentation, pickle brine usually becomes cloudy and develops a slightly sour aroma; in contrast, a sharp, unpleasant odor or mold growth is a serious sign of spoilage.

In homemade fermented dairy products such as kefir, yoghurt, and strained yoghurt, healthy fermentation is typically indicated by a mild sour and yeasty aroma. However, over-fermentation, poor hygiene, or improper storage conditions can lead to spoilage. This is recognizable through visual and olfactory signs such as mold, sharp sour or ammonia-like odors, pink, blue, green, or black spots, and swollen packaging. These signs indicate that the product is unsafe and should not be consumed.

Healthy fermentation in homemade tarhana is also characterized by a mild sour and yeasty aroma. Spoiled tarhana may exhibit sharp, moldy, or musty odors; white, green, or black spots; and changes in color and texture. These signs indicate that the product is unsafe and should not be consumed.

During the fermentation of homemade kumis, a slightly sour and yeasty aroma is considered normal. However, undesired changes in sensory characteristics may indicate that the product is of poor quality or has spoiled.

1. All surfaces that come into contact with food, the preparer’s hands, and the containers used for fermentation should be carefully washed and dried. This practice supports the growth of desired fermentative microorganisms while helping to reduce the number of other bacteria and yeasts.
2. Factors such as pH, duration, and temperature are critical for achieving the desired flavor and texture in fermented products. For fermented vegetables or yoghurt, the product’s pH should be below 4.6. This value can be easily tested using commercial pH strips or measurement devices.
3. The raw materials used in fermentation must be fresh and clean. To prevent spoilage and the introduction of harmful microorganisms into yoghurt, it is recommended to use commercially or home-pasteurised milk. For vegetables, select fresh, unspoiled, and disease-free products. High-quality raw materials enhance both the success of fermentation and food safety.
4. Since fermented vegetables are often active and bubbly, when using a wide-mouth jar, it should not be overfilled, leaving about 5 cm of headspace. If brining is preferred, the jar should be filled to the top, as excessive headspace can lead to oxygen accumulation, causing mold or foam formation. Additionally, non-iodized salt should be used in the brine.