Use of central composite design in food microbiology: a case study on the effects of secondary phenols on lactic acid bacteria from olives

Abstract

This paper focuses on the use of statistical Design of Experiments (DoE) to investigate the effects of two anti-lactic acid bacteria compounds on growth and metabolism of lactobacilli isolated from Italian table olives. p-Coumaric and vanillic acids (0.0–0.4%) were used as phenolic compounds, which were combined with salt (0.0–6.0%) and glucose (0.0–4.0%) through a Central Composite Design. Three strains of Lactobacillus plantarum (5 log cfu/ml) were used as test organisms, samples were stored at 37 °C, and cell counts and pH were evaluated periodically. The growth of lactobacilli was affected in a significant way by salt, p-coumaric and vanillic acids, being the salt the most significant factor after 24 h (short storage time), then replaced by p-coumaric acid. p-Coumaric acid also played a significant role on the acidifying ability, expressed as decrease of pH of the medium: microbial metabolism, in fact, appeared as completely inhibited at 0.2% of p-coumaric acid.

• Central composite design
• growth
• lactic acid bacteria
• phenolic compounds
• pH

Declaration of interest

This paper was supported by the Italian Ministry of Education, University and Research through the Grant PROINNOBIT (Sviluppo di prodotti alimentari innovativi mediante soluzioni biotecnologiche, impiantistiche e tecnologiche – PON02_00186_3417037 – Development of innovative food products through biotechnological, plant design and technological solutions) – PON Ricerca e Competitività 2007–2013 – Programma Cofinanziato dal Fondo Europeo di Sviluppo Regionale (FESR).