Effects of Nettle (Urtica dioica) Extract on Versus Pathogenic Microorganisms in Yogurt Production

Abstract

Contamination with pathogenic bacteria is the most common cause of foodborne illness and represents a public health problem worldwide. These pathogens can be controlled by adding extracts to fermented milk. In the present study, the effects of nettle extract on selected pathogenic bacteria in yogurt production were investigated. For this purpose, the antibacterial effectiveness of the extract additives in the presence of bacteria was examined and compared. Yoghurt samples, 24 different samples contaminated with 7 standard pathogen strains, were analyzed for chemical properties (pH and acidity) and antimicrobial activity after 1, 7, 14 and 21 days of storage at 4 °C. In particular, it was found that the decrease in pH and increase in acidity in the nettle extract samples after 21 days were significantly greater than in natural yogurt and yogurt samples containing nettle extract (0.5% and 1%, respectively) (p<0.05). Pathogens were reduced more significantly in samples treated with nettle extracts, which have antibacterial activity against pathogens. In particular, compared to natural yogurt, these samples showed significant antibacterial effects on the standard strains Streptococcus pneumoniae ATCC 45615, Klebsiella pneumoniae ATCC 70063 and Pseudomonas aeruginosa ATCC 27853 (p<0.01). Furthermore, in the samples containing nettle extract, the 1% concentration had synergistic effects on Streptococcus pneumoniae ATCC 45615, while the 0.5% concentration had synergistic effects on Klebsiella pneumoniae ATCC 70063 and Pseudomonas aeruginosa ATCC 27853. Overall, these results suggest that the nettle extract could be used as a natural preservative to improve the safety of yogurt and other dairy products.

Keywords

• Antimicrobial activity
• Physicochemical properties
• Nettle extract
• Yogurt

Yoğurt Üretiminde Isırgan Otu (Urtica dioica) Ekstraktının Patojenik Mikroorganizmalara Karşı Etkileri

Abstract

Patojenik bakteri kontaminasyonu, küresel bir halk sağlığı sorunu olan gıda kaynaklı hastalıkların önde gelen nedenleri arasında yer almaktadır. Bu patojen mikroorganizmalar fermente süt üretiminde kullanılan ısırgan otu ekstraktları ile kontrol altına alınabilir. Bu çalışmada ısırgan otu (Urtica dioica) ekstraktının yoğurt üretiminde seçilmiş patojen bakteriler üzerindeki etkileri değerlendirilmiştir. Bu amaçla bakterilerin bulunduğu ortamda ekstrakt takviyelerinin antibakteriyel etkinliği araştırılmış ve karşılaştırmaları yapılmıştır. 24 farklı yoğurt örneği 7 standart patojen suşla kontamine edildikten sonra kimyasal özellikleri (pH ve asitlik) ile antimikrobiyal aktiviteleri açısından 4oC depolama sıcaklığında ve 1., 7., 14. ve 21. depolama günlerinde analiz edilmiştir. Özellikle ısırgan otu ekstraktlı örneklerde pH değerlerinde azalma ve asitlik değerlerindeki artışın, kontrol yoğurdu ile ısırgan otu ekstraktı içeren (%0.5 ve %1) örnekler arasındaki karşılaştırmaya göre 21 gün boyunca istatistiksel olarak daha anlamlı olduğu belirlenmiştir (p<0.05). Patojenlere karşı antibakteriyel aktiviteye sahip olan ısırgan otu ekstraktları ile muamele edilen örneklerde patojenlerin daha belirgin şekilde azaldığı saptanmıştır. Özellikle bu örneklerden Streptococcus pneumoniae ATCC 45615, Klebsiella pneumoniae ATCC 70063 ve Pseudomonas aeruginosa ATCC 27853 standart suşları ile hazırlananların kontrol yoğurtla karşılaştırıldığında anlamlı antibakteriyel etki gösterdiği tespit edilmiştir (p<0.01). Ayrıca ısırgan otu ekstraktı içeren örnekler arasında %1'lik konsantrasyon Streptococcus pneumoniae ATCC 45615'e karşı daha iyi bir etki gösterirken, %0.5'lik konsantrasyon hem Klebsiella pneumoniae ATCC 70063 hem de Pseudomonas aeruginosa ATCC 27853'e karşı daha fazla etki sağladığı belirlenmiştir. Genel olarak araştırma bulguları ısırgan otu ekstraktının yoğurt ve diğer süt ürünlerinin güvenliğini arttırmak için doğal bir koruyucu madde olarak kullanılabileceğini göstermiştir.

Keywords

• Antimikrobiyal aktivite
• Fizikokimyasal özellikler
• Isırgan otu ekstraktı
• Yoğurt

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