1 3 Eur Food Res Technol (2016) 242:1803–1811 DOI 10.1007/s00217-016-2724-y SHORT COMMUNICATION Setup of a procedure for cider proteins recovery and quantification Federica Mainente 1,2 · Corrado Rizzi 2 · Gianni Zoccatelli 2 · Roberto Chignola 2 · Barbara Simonato 2 · Gabriella Pasini 1 Received: 29 January 2016 / Revised: 17 May 2016 / Accepted: 1 June 2016 / Published online: 7 June 2016 © Springer-Verlag Berlin Heidelberg 2016 Introduction Cider is a slightly alcoholic beverage (generally from 3 to 8 % of alcohol volume) resulting from the fermentation of apple must. It is produced in more than 25 countries, and it is widespread throughout the world [1]. The main pro- ducers in Europe are the UK, Ireland, France and Northern Spain [2]. As other fermented beverages, cider is a complex matrix, whose main constituents are water, ethanol, sugars (mainly fructose), organic acids (essentially malic acid), phenolic and aromatic compounds [3]. Minor constituents are proteins that might play different important roles in the product characteristics [4–6]. Indeed, studies on other fer- mented beverages have shown that proteins are involved in the foam stability, can interact with aroma compounds [7–9], and are also responsible for the formation of hazes and sediments [10–15]. It is well known that proteins may undergo modifications (such as hydrolysis, denaturation and/or aggregation) during the food processing [16, 17]. These physicochemical changes could modify not only the protein functional properties, but also their digestibility and potential allergenicity [18]. For these reasons, it is impor- tant to have reliable methods to study cider protein profiles. Because of the large number of compounds present in fermented beverages, purification and characterization of proteins usually represent a difficult task. Previous works report different methods to remove compounds, like phe- nols, carbohydrates or salts, that can interfere with the qual- itative and quantitative analyses of proteins [10, 19–22]. The most common approaches to isolate proteins from beverages involve physical (i.e., dialysis, ultrafiltration and gel filtration) or chemical methods (e.g., precipitation by organic solvents, TCA, ammonium sulfate, sulphosalicylic Abstract Cider contains low amount of proteins that, nonetheless, can affect its stability, foam formation and potential allergenicity. At present, scarce information is available on cider proteins, probably due to the lack of methods for their recovery and analysis. The aim of the present study was to set up a method for recovering and quantifying cider proteins. To this purpose, the proteins from 13 Italian commercial ciders were recovered by dialy- sis, gel filtration, trichloroacetic acid/acetone (TCA/ace- tone) and potassium dodecyl sulfate (KDS) precipitation. The protein content of the samples was then determined by bicinchoninic acid (BCA), Bradford and o-phthaldi- aldehyde (OPA) assays. The results were compared to quantitative data obtained by densitometry of electropho- retic gels. The most reliable protocol resulted in the KDS method followed by OPA assay. KDS, in addition, allowed also to separate proteins from glycocompounds. KDS/OPA is the method of choice for cider proteins precipitation and quantification. Keywords Cider · Proteins recovery · Proteins quantification · KDS · o-Phthaldialdehyde (OPA) assay Electronic supplementary material The online version of this article (doi:10.1007/s00217-016-2724-y) contains supplementary material, which is available to authorized users. * Federica Mainente federica.mainente@univr.it 1 Department of Agronomy Food Natural Resources Animals and Environment, University of Padova, Agripolis, Viale dell’Università, 16, 35020 Legnaro, Padova, Italy 2 Department of Biotechnology, University of Verona, Verona, Italy