Forced syneresis determination results from comercial cream cheese samples

Abstract

pH, ζ-potential and ionic calcium of 26 commercial cream cheese samples were determined along with forced syneresis by stepwise centrifugation and the results analysed in consideration of their gross composition to create three statistical models. The first model evaluated all samples and revealed that those with high salt content had significantly lower serum release with a threshold of 0.66 g NaCl 100 g-1 partitioning 5 samples from the rest. Higher fat content had a similar effect. The second model only considered samples without added stabilisers, identifying fat and protein to be the fundamental factors that contained syneresis. Aligning with model 1, the third model only considered samples with stabilisers, confirming salt to be the influencing parameter to decrease serum release showing the dominating effect of hydrocolloids on syneresis in cream chesse. ζ-Potential and pH had no significant effect. Forced syneresis was on average 6.4% and 27.1% in cheeses with/without stabilisers.

Introduction

Cream cheese is a Dairy product produced generally by blending milk and cream, involving milk pre-treatments, standardising fat level, acidifying with bactéria, concentrating (whey or permeate separation) and adding other ingredients like salt and hydrocolloids, followed by known processing steps like mixing, pumping, homogenising, heating, filling and cooling, to treat the the curd. For details, the reader is referred to the excelente reviews on acid curd cheeses including cream cheese made by Guinee, Pudja and Farkye (1993), Lucey (2004) and Schulz-Collins and Senge (2004).

Cream cheese has many different end-use applications wordwide. One major determinant quality fator is syneresis, derived from the structural rearrangements of the casein micelles during processing and shelf life (Guinee, 2016; Lucey, 2004). The breaking and formation of (inter- and intra-) casein bonds affect the syneresis behaviour in the product, i.e., whey or serum release and this phenomenon likely continues during storage. During the milk acidification a progressively pH-induced colloidal calcium phosphate solubilisation and charge modifications on the casein micelles occur (Lucey, 2004); the net-negative charge (ζ-potential) of the casein micelles decreases with reduction in pH, thus changing the matrix stability. Both the ζ-potential (responsible for electrostatic repulsion) and the ionic Ca (charge neutralisation, shielding) are factors involved in the interactions within the cheese matrix protein components and serum phase. The charge is onde key fator responsible for the structure-function of caseins because of its effect on hydrophilicity/hydrophobicity balance (Broyard; Gaucheron, 2015). Since the pH governs the physical-chemical changes and has an influence in the serum phase, the functionality of the acidified caseins i salso affected (Broyard; Gaucheron, 2015). The salt content and the pH of the cheese affects is degree of hydratation (Guinee, 2016; Schokoda; Hechler; Kessler, 1999).

According to Voyutski (1978) syneresis occurs when the dispersion médium is pressed out of a gel due to particles rearrangements within the gel structure, which increase the number of contacts between the structural elements in the gel matrix, When initially not all possible contact points in the particles were expended during gel formation. Van Vliet and Walstra (1994) demonstrated that it is the structure of the casein aggregates in the gel which governs the water release from it. Recently Ouanezer, Guyomarc’h, and Bouchoux (2012), suggesting an sponge like structure for the casein micelles, showed evidence of the rearrangements and packing processes during/after milk acidification, which according to them are induced by the loss of colloidal calcium phosphate and the increase in the net attraction between proteins and shrinking of the micelles to smaller sizes due to loss in charge.

The micellar rearrangements during the acidification process are dependente on the casein concentration and the aggregation process is determined by the interfacial properties of the casein particles (Moitzi; Menzel; churtenberger; Stradner, 2011). Trejo, Dokland, Fuentes and Harte (2011) demonstratred the presence of water filled cavities, channels and high density nanoclusters in casein micelles and suggested a sponge-like structure for them based on cryo-transmission electronmicroscopy studies. De Kruif, Anema, Zhu, Havea, and Coker (2015) demonstrated that the water holding capacity of a caseinate gel depends on the interactions with the aqueous phase and cross linking of the caseins in the gel. In a very recente study abaout casein hydration, Huppertz et al. (2017) made a distinction for the different forms in which water might be found in the casein micelles and described the latter as a porous network of primary casein particles linked by the calcium phosphate nanocluster.

Syneresis can be determined and expressed in different ways. Guinee (2016) and Schokoda (1999), among others, showed that the amount of whey expelled on centrifugation of Quark cheese is clearly dependent on the centrifugal g-force Applied. Hence, just determining the total amount of whey released (%, w/w) is not enought to understand the ease of removal of water from, and stability of, a cream cheese product. In this paper we define forced syneresis as the amount of whey (serum, water phase) expelled fromcertain amount of gel (an acid curd) after applying a stepwise external pressure via centrifugal g-force. Furthermore, in the presente study, we have determined also the ζ-potential, the pH value and the ionic Ca2+ concentration of comercial cheese products and Applied statistical treatments to explore the relation between gross composition and physical-chemical properties on the forced serum release.       

Conclusions

The stability of a cream cheese matrix against syneresis could be easy evaluated by applying a sequential increase in g-force to cheese samples. In cheeses without added hydrocolloids, forced serum release occured already at very low g-force(s), whereas some cheeses with added hydrocolloids did not expel serum even at the highest g-force applied. In the latter cheeses, total forced syneresis was on average four times lower than in the former products. This highlights the importance of stabilisers (type and amount) for syneresis reduction and quality of the product. The addition of gums, which influences the viscosity of the serum phase, overshadowed the positive effect of fat and protein on syneresis reduction observed in cheeses without added stabilisers, and left the added salt as the only influencing fator in those cheeses. Hence, salt addition ssems to play another role in cream cheese besides flavour, discriminating between cheeses with low and high level of forced syneresis. Physical-chemical changes in pH, ζ-potential and Ca2+ activity, which occurred during the milk fermentation step, did not heve an influence on the forced syneresis in cheeses with added hydrocolloids and only a minor effect in cheeses without added gums. The presente snapshot view of the forced syneresis situation in comercial cream cheese samples clearly put in evidence the major role of added hydrocolloids and need for (clean labelling) research in syneresis for this type of cheese.

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[121] WOLFSCHOON-POMBO, A.; DANG, B. P.; CHIRIBOGA, B. C. Forced syneresis determination results from comercial cream cheese samples. International Journal of Dairy Technology, v. 69, p. 4-28, 2018.