Identification of Bacterial Species Isolated from Biscuits in Response to their Storage Period

Abstract

The objective of the current work was to evaluate basic technological parameters of three types of biscuits including moisture content (MC) and water activity (aw), and to characterize their microbial spoilage (related to the total bacterial count, presence of coliform bacteria, yeasts and moulds, and their specific identification) during the 42-days of storage period in laboratory conditions (temperature: 20 ± 2 °C, relative humidity: 62 ± 1%). For these purposes, Kern DBS 60-3 and Lab Master aw Standard, as well as MALDI-TOF MS Biotyper were used for the analyses. The results from the technological analysis showed that values for MC and aw of the biscuits ranged from 5.07 ± 0.03% to 13.59 ± 0.13%, and from 0.467 ± 0.022 to 0.857 ± 0.001, respectively, depending on their recipe formulas. The microbiological characterisation of the biscuit samples revealed the absence of coliform bacteria and fungi throughout the storage period, reflecting that the biscuits production was kept in appropriate hygienic conditions. However, from the 14th day of storage, the presence of some bacterial species was detected in the biscuit samples. Among them, Bacillus subtilis which is frequently occurring bacteria in bakery products causing ropiness of the products was the most represented. Our results allow for the conclusion that the biscuits developed in our laboratory are safe for the consumers and their minimum shelf life is approximately two weeks.

Keywords

• confectionery goods
• storage
• microorganisms
• spectrophotometry