Sunflower meal ethanol solute powder as an upcycled value-product to prolong food shelf life

Abstract

In this study the potential of sunflower meal ethanol-wash powder (SEWP) to be used as antimicrobial agent in liquid foods was investigated. SEWP represents the waste of the main process of protein isolation from industrially produced sunflower meal. The washing liquids remaining after treatment of the sunflower meal with 75% aqueous ethanol solution were collected and turned into powder rich in bioactive compounds. Due to its recognized properties, different concentrations (2.5 and 5% w/v) of SEWP were first tested in vitro against Alicyclobacillus acidoterrestris and a cocktail of Pseudomonas putida and Pseudomonas fluorescens strains, using appropriate culture media. Then, the SEWP antimicrobial efficacy was tested on two real food matrices differing in their composition. Soymilk, rich in proteins, and apple juice, composed mainly of carbohydrates, were used as food models. Concentrations equal to 1%, 1.5%, 2%, 2.5%, 5% and 7.5% (w/v) SEWP were tested in the juice, whereas the sole three highest concentrations were tested in the soymilk. Both beverages were pre-inoculated with different spoilage bacteria. The same mix of Pseudomonas spp. and A. acidoterrestris strain used for the in vitro test were employed to contaminate the soymilk and the apple juice, respectively. In vitro results showed moderate effects of SEWP against selected target microorganisms. On the contrary, two completely different microbial evolutions were recorded in the soymilk and apple juice. The three concentrations of SEWP were slightly effective against spoilage of soymilk, whereas all the concentrations used in the juice were sufficient to completely inhibit microbial growth of A. acidoterrestris. The shelf life of the apple juice supplemented with 1% SEWP was extended for more than 21 days. Considering both the antimicrobial efficacy and the sensory properties of the juice, the lowest SEWP concentration (1% w/v) demonstrated the best result as a bioprotectant. Overall results imply dependence of SEWP antimicrobial efficiency on food composition and a need of preliminary evaluation of the product if used as an antimicrobial agent in the food industry.