Inactivation of Penicillum expansum in sour cherry juice, peach and apricot nectars by pulsed electric fields

• Published in: Food microbiology 2008-08, Vol.25 (5), p.662-667
• Main Authors: Evrendilek, Gulsun Akdemir, Tok, Fatih M., Soylu, E. Mine, Soylu, Soner
• Format: Article
• Language: English
• Subjects: Apricot nectar; apricots; Beverages - microbiology; Biological and medical sciences; cherries; Colony Count, Microbial; conidia; cytoplasm; decontamination; Electricity; food contamination; Food Contamination - prevention & control; Food Handling - methods; Food industries; Food Microbiology; Food Preservation - methods; Fruit - microbiology; Fruit and vegetable industries; fruit juices; Fundamental and applied biological sciences. Psychology; Germ tube elongation; Germination; Humans; microbial contamination; Microscopy, Electron, Scanning; Peach nectar; peaches; Penicillium - growth & development; Penicillium - ultrastructure; Penicillium expansum; Penicillum expansum; processing stages; protoplasts; Prunus; pulsed electric fields; Pulsed electric fields (PEF); Sour cherry juice; spoilage; spoilage microorganisms; Spore germination; Spores, Fungal - growth & development; Spores, Fungal - ultrastructure; Time Factors
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2008.03.009

Inhibitory effects of pulsed electric fields (PEF) on Penicillum expansum inoculated into sour cherry juice, apricot and peach nectars were determined based on germination tube elongation, spore germination rate, and light and scanning electron microscopy (SEM) observations in this study. After inoculation of juice/nectar samples with P. expansum spores at the level of 10 5–10 6 cfu/mL, the samples were processed by bench scale PEF pulse generator as a function of differing electric field strengths (0, 13, 17, 20, 23, 27, 30 and 34 kV/cm) and processing times (0, 62, 94, 123, 163, 198 and 218 μs). Results revealed that with an increase in electric field strength and processing time, germination tube elongation and spore germination rate were completely inhibited. Light and SEM observations revealed considerable morphological alterations in fungal conidia such as cytoplasmic coagulation, vacuolations, shrinkage and protoplast leakage. PEF processing of juice/nectars was demonstrated to be effective in inactivating P. expansum. To our knowledge, this is the first study confirming the inhibitory effects of PEF on germination tube elongation and spore germination rate of P. expansum in fruit juice/nectars.