Abstract
Alicyclobacillus acidoterrestris is a spoiling microorganism regarded as one of the most important causes of spoilage of fruit juices and acidic products. In this paper, four strains of A. acidoterrestris (type strain-DSM 3922; two wild strains isolated from soil-C8 and C24; wild strain isolated from a spoiled pear juice CB1) were treated through natural extracts/active compounds from essential oils (EOs), and physical treatments were used to assess their susceptibility and the presence of sublethal injury. The characterization of damage was also performed. The results suggest that it is possible to control A. acidoterrestris through alternative approaches, although the effect relied upon the age of spores. In addition to the mere antimicrobial effect, some treatments could cause a sublethal injury on spores. Lemon extract was the most effective treatment for both the antimicrobial effect and the sublethal injury, as evidenced by the release of proteins, and calcium dipicolinate [dipicolinic acid (DPA)] by fresh spores and only DPA (with an exception for C8) by old spores. A sublethal injury with protein release was also found for physical treatments [US (ultrasound) or heating]. For the first time, this paper reports on the existence of a sublethal injury for A. acidoterrestris, and this evidence could also be a challenge, because injured microorganisms could restore their metabolism, or an opportunity to design new preserving treatments.
Highlights
Alicyclobacillus acidoterrestris is a spoiling microorganism regarded as one of the most important causes of spoilage of fruit juices and acidic products; it is a control target for thermal treatment effectiveness [1]
The use of essential oils (EOs), natural extracts, and their active components was suggested as a mean to delay or inhibit A. acidoterrestris in acidic foods [30,31,32], because some natural molecules are extracted from plants and fruits; they are not perceived by consumers as chemicals, but as a part of product or natural compounds
A. acidoterrestris is a threat in fruit juices and acidic products, but the results of this paper confirm that it is possible to control A. acidoterrestris through alternative approaches, a variable to be considered is the age of spores
Summary
Alicyclobacillus acidoterrestris is a spoiling microorganism regarded as one of the most important causes of spoilage of fruit juices and acidic products; it is a control target for thermal treatment effectiveness [1]. It represents a threat of spoilage in acidic foods because spores can germinate and grow at low pH [2]. Fruit juices generally undergo a flash treatment (temperature/short time) to avoid loss in organoleptic and nutritional properties [6, 7], but A. acidoterrestris spores can survive [8, 9]
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