High-Pressure-Based Strategies for the Inactivation of Bacillus subtilis Endospores in Honey
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abstract
Honey is a value-added product rich in several types of phenolic compounds, enzymes, and
sugars recently explored in biomedical and food applications. Nevertheless, even though it has a low
water activity (aW = 0.65) that hinders the development of pathogenic and spoilage microorganisms,
it is still prone to contamination by pathogenic microorganisms (vegetative and spores) and may constitute
harm to special groups, particularly by immunosuppressed people and pregnant women. Thus,
an efficient processing methodology needs to be followed to ensure microbial safety while avoiding
5-hydroxymethylfurfural (HMF) formation and browning reactions, with a consequent loss of biological
value. In this paper, both thermal (pressure-assisted thermal processing, PATP) and nonthermal
high-pressure processing (HPP), and another pressure-based methodology (hyperbaric storage,
HS) were used to ascertain their potential to inactivate Bacillus subtilis endospores in honey and to
study the influence of aW on the inactivation on this endospore. The results showed that PATP at
600 MPa/15 min/75 C of diluted honey (52.9 Brix) with increased aW (0.85 compared to 0.55,
the usual honey aW) allowed for inactivating of at least 4.0 log units of B. subtilis spores (to below
detection limits), while HS and HPP caused neither the germination nor inactivated spores (i.e., there
was neither a loss of endospore resistance after heat shock nor endospore inactivation as a consequence
of the storage methodology). PATP of undiluted honey even at harsh processing conditions
(600 MPa/15 min/85 C) did not impact the spore load. The results for diluted honey open the
possibility of its decontamination by spores’ inactivation for medical and pharmaceutical applications.
