Influence of calcium on white efflorescence formation on dry fermented sausages with co-extruded alginate casings
Graphical abstract
Introduction
Co-extrusion of calcium alginate casings on food, especially on dry fermented sausages, is an emerging technology, which is due to the fact that producers can move from batch processing to continuous processing with increased product volume (Harper, Barbut, Smith, & Marcone, 2015). Moreover, the production of meat snack products with very small calibers is possible, which would not be possible with natural casings (Gennadios, Hanna, & Kurth, 1997). For example, in meat products they are used on dry fermented sausages with small calibers (Hilbig et al., 2019, Walz et al., 2018) or on breakfast pork sausages (Liu, Kerry, & Kerry, 2007). During the co-extrusion process, a thin film of alginate is applied to the surface of the product, and subsequently crosslinked in a calcium chloride bath (Harper et al., 2015). The divalent calcium cations applied now bind to the guluronate blocks of the alginate, thereby forming junctions between different alginate chains, which results in a gel structure, the so-called egg-box model (Grant, Morris, Rees, Smith, & Thom, 1973).
The disadvantage of the application of calcium alginate casings on meat products is the formation of white crystals on the surface, the so-called white efflorescence. The formation is a physical mass transport phenomenon of dissociated acids and minerals from the core of the sausages to the surface. It is a big issue for the meat processing industry, because the affected products are rejected by the consumer because of misjudging it as microbial spoilage (Walz, Gibis, Herrmann, Hinrichs, & Weiss, 2017). Dry fermented sausages are mainly affected by the formation of the crystals (Hilbig et al., 2019, Walz et al., 2018, Walz et al., 2017, Walz et al., 2018), and so are dry cured hams (Arnau et al., 1994, Arnau et al., 1996, Arnau et al., 1993). Efflorescence normally occurs on meat products which are stored at low temperatures and are packed under modified atmosphere (Arnau, Guerrero, & Gou, 1998). There are three types of efflorescences: efflorescences consisting of disodium phosphate heptahydrate (Arnau et al., 1998), efflorescences consisting of creatine monohydrate (Kröckel, Jira, Kühne, & Müller, 2003), and efflorescences consisting of magnesium or calcium lactate (Hilbig et al., 2019, Walz et al., 2017). Walz, Gibis, Herrmann, et al. (2017) showed that magnesium was identified as one of the main efflorescence-causing substances, resulting in the irreversible efflorescence type II. In the study of Hilbig, Murugesan, et al. (2019), it was shown that the application of calcium alginate casings cause a fast formation of white efflorescence on the surface of dry fermented sausages. This effect was attributed to the excess of calcium on the surface because of the crosslinking of the alginate gel with calcium chloride (Rhim, 2004). To inhibit the formation of white efflorescences on dry fermented sausages with collagen casings different methods were investigated, such as the application of phosphates (Walz et al., 2018, Walz et al., 2017), the smoke intensity (Walz, Gibis, Herrmann, & Weiss, 2019), and the variation of the drying conditions (Walz, Gibis, Koummarasy, et al., 2018). The application of phosphates and strong smoking inhibited successfully the white efflorescence formation; however, the strong smoking of the product influenced the sensory negatively. Compared to that, on dry fermented sausages with calcium alginate casings an excess of calcium is present on the surface due to the calcium chloride crosslinking solution forming a stable polymer film. The white efforescences on the surface of these sausages consisted mainly of calcium and no magnesium ions. This suggests that a different mechanism of formation is at play, and it puts at question whether the previously developed solutions are applicable to these products. Moreover, the stability of the casing needs to be considered. For example the application of a phosphate surface treatment successfully inhibited the crystal formation however the calcium alginate casing was destabilized due to the removement of calcium (Hilbig, Murugesan, et al., 2019). Furthermore, in the study of Hilbig, Hartlieb, Herrmann, Weiss, and Gibis (2019) different chelators were introduced into the calcium alginate casing and only the application of polyphosphates and citric acid could reduce the crystal formation but did not completely inhibit it.
Since the influence of magnesium on white efflorescence formation on dry fermented sausages with collagen casings is well understood (Walz, Gibis, Herrmann, et al., 2017) the effect of calcium ions on the crystal formation is largely unknown. However, previous studies indicated that calcium could influence the white efflorescence formation (Hilbig et al., 2019, Hilbig et al., 2019). Therefore, information is needed to what extent calcium is influencing the crystallization and if magnesium or complexes of magnesium lactate are needed to induce the crystallization (for example as crystallization nucleus). For the mechanistic context, it is important to consider the individual cations separately and independently of each other in a model system. Therefore, the purpose of the current study was to investigate the influence of different calcium chloride concentrations in the crosslinking solution during dry fermented sausage production on the white efflorescence formation. To do so, four different concentrations of calcium chloride solution (15, 20, 25, and 30%) were applied. These concentrations were selected because 25% and 30% are common concentrations used in the industrial settings of crosslinking baths, and due to limits in casing stability; i.e. a stable coextrusion and crosslinking process for casings can no longer be ensured below concentrations of 15%. The hypothesis was that with increasing concentrations of calcium in the crosslinking solution the white efflorescence formation would be more intensive and faster compared to lower concentrations. In addition, there would be an optimal concentration with reduced formation of efflorescence as well, as without loss of the stability of the casings.
Section snippets
Production of sausage and sample preparation
The meat for the experiments was standardized according to the meat classification system to SII (pork shoulder without fat tissue where the sinews have been largely removed with a maximal visual fat content of 5%) and SVIII (back fat without rind) (Hack, Gerhardt, & Staffe, 1976). The meat was purchased from a local wholesaler (MEAG eG, Stuttgart, Germany). The meat batter was composed of 35% minced lean pork shoulder SII (3 mm whole plate, WD 114, Seydelmann GmbH, Aalen, Germany; 2 °C), 45%
Appearance, sensory and image analysis of the dry-fermented sausages
The calcium alginate casings produced were all stable independent of the calcium chloride concentration used for the crosslinking. Tensile tests of the different casings showed only minor differences between the concentrations (Table 1). In Fig. 1, the appearance of the different batches during the storage of 8 weeks is shown. The batches produced with 15 and 20% of CaCl2 solutions showed no efflorescence formation immediately after the production (0 weeks), whereas in the batches produced with
Proposed mechanism
Fig. 6 illustrates the proposed mechanism of the formation. Furthermore, the investigation showed two ways the crystals on the surface are formed:
- i.
High concentration of calcium in the crosslinking solution
At high concentrations of calcium in the crosslinking solution, the gel is saturated with calcium and high amounts of unbound calcium accumulates on the surface of the sausage. During the storage, lactate is complexed by the calcium ions, thereby forming the white crystals. This leads to the
Conclusion
The present study showed that the amount of calcium in the crosslinking solution has an impact on the amount, speed of formation, and type of white efflorescence, which is formed during the storage. High concentrations promote the formation of complexes of calcium and lactate and, because of the excess of calcium, the formation happens quite fast. However, at low concentrations of calcium, the formation is slower due to the complexation of magnesium with lactate instead of calcium. The
CRediT authorship contribution statement
Jonas Hilbig: Conceptualization, project administration, data curation, writing - original draft. Katrin Hartlieb: Investigation (master thesis). Kurt Herrmann: Supervision - pilot plant. Jochen Weiss: Conceptualization, supervision, writing - review & editing. Monika Gibis: Conceptualization, project administration, supervision, writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This IGF Project (AiF 19689N) of the FEI is/was supported via AiF within the program for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a resolution of the German Parliament.
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