*Article* **Technological Strategies to Preserve Burrata Cheese Quality**

**Cristina Costa 1, Annalisa Lucera 1, Amalia Conte 1,\*, Angelo Vittorio Zambrini <sup>2</sup> and Matteo Alessandro Del Nobile <sup>1</sup>**


Received: 4 May 2017; Accepted: 4 July 2017; Published: 9 July 2017

**Abstract:** Burrata cheese is a very perishable product due to microbial proliferation and undesirable sensory changes. In this work, a step-by-step optimization approach was used to design proper processing and packaging conditions for burrata in brine. In particular, four different steps were carried out to extend its shelf life. Different headspace gas compositions (MAP-1 30:70 CO2:N2; MAP-2 50:50 CO2:N2 and MAP-3 65:35 CO2:N2) were firstly tested. To further promote product preservation, a coating was also optimized. Then, antimicrobial compounds in the filling of the burrata cheese (lysozyme and Na2-EDTA) and later in the coating (enzymatic complex and silver nanoparticles) were analyzed. To evaluate the quality of the samples, in each step headspace gas composition, microbial population, and pH and sensory attributes were monitored during storage at 8 ± 1 ◦C. The results highlight that the antimicrobial compounds in the stracciatella, coating with silver nanoparticles, and packaging under MAP-3 represent effective conditions to guarantee product preservation, moving burrata shelf life from three days (control sample) to ten days.

**Keywords:** burrata cheese; shelf life; antimicrobial coating; packaging design

#### **1. Introduction**

Burrata is a fresh Italian cheese, typically produced in the Apulia region, made from fiordilatte paste and a cream called stracciatella. The outer shell is solid fiordilatte paste while the inside contains both fiordilatte pieces and cream, giving it a soft texture. Burrata is traditionally stored under refrigerated conditions, like fiordilatte and mozzarella cheese, and it can be packaged with or without brine in atmospheric conditions. Due to the high moisture and fat content, this dairy product results in rapid spoilage. It is well-known that the shelf life of fresh cheese is influenced by both microbial and sensory changes [1–3]. To preserve the characteristics of fresh cheese during storage several techniques have been suggested in the literature [4–6]. Several authors demonstrated the effects of modified atmosphere conditions (MAP) on extending the shelf life of fresh cheese [2,3,7].

In particular, the headspace gas composition characterized by a low concentration or lack of oxygen and high carbon dioxide improves the microbiological stability, reduces lipid oxidation and increases sensory acceptability [1,2,8]. A proper successful gas combination for burrata cheese packaged without brine was proposed by Conte et al. [9]. The application of antimicrobial compounds, such as essential oils, organic acids, bacteriocins and nanoparticles, was also found to be a strategic solution to improve the shelf life of different fresh cheeses [6,10–13]. To retard the microbial spoilage of dairy products, the antimicrobial compounds can be directly added into the product formulation, carried by coatings or loaded into the packaging materials. Among them, a great deal of attention has been devoted to inorganic nanoparticles (i.e., silver and copper) for their proven effects on the microbial stability of various foodstuffs [13–18]. In particular, scientific research has reported that silver nanoparticles immobilized on packaging materials or loaded in coatings improves the shelf life of mozzarella [12,17,19]. Enzymes can also play an interesting role in antimicrobial activity [6].

In particular, lysozyme, an enzyme found in many natural systems, shows antimicrobial activity against gram-positive bacteria more than gram-negative; however, the susceptibility of gram-negative bacteria can be enhanced by chelating agents such as ethylene diamine tetraacetic acid disodium salt (Na2-EDTA). Different works have reported the antimicrobial activity of lysozyme alone or in combination with Na2-EDTA [9,20,21]. The lactoperoxidase system—an enzymatic complex characterized by the lactoperoxidase enzyme, thiocyanate and hydrogen peroxide—is also active against gram-positive bacteria such as *Listeria monocytogenes* and *Staphylococcus aureus,* as well as gram-negative bacteria, including *Escherichia coli* [22,23]. The activity of the lactoperoxidase system has been verified on many bacterial species and pathogens in cow milk and dairy products [24,25].

To the best of our knowledge, no studies have reported on the packaging of burrata cheese with brine. The brine solution better preserves product hydration but it also concurs with the development of spoilage microorganisms. Therefore, the aim of this study was to evaluate step by step the influence of MAP, lysozyme and Na2-EDTA in the burrata filling and the adoption of a proper active coating on burrata cheese shelf life. To assess the influence of the selected strategies, headspace gas composition, pH, spoilage microorganisms and sensory quality were monitored during the storage period.

#### **2. Materials and Methods**
