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Volatile Organic Compounds In Split, Nonsplit Swiss Cheese Samples Analyzed

Chicago—A study published in the April edition of the IFT’s Journal of Food Science evaluated the applicability of selected-ion flow tube mass spectrometry (SIFT-MS) for the analysis of volatile organic compounds in split and nonsplit Swiss cheese samples.

The study was written by Hardy Z. Castada, Cheryl Wick, Kaitlyn Taylor, and W. James Harper, all with the department of food science and technology at Ohio State University.

Splits/cracks are product defects that are a recurring problem in the manufacture of Swiss cheese, the study explained. These defects downgrade the cheese and its market value, creating a considerable economic loss to the industry.

Splits are undesirable openings in Swiss cheese that commonly occur during the cold ripening process, with temperatures ranging between 0 and 2 degrees C. During this cold storage, the cheese loses its elasticity and, at low temperature, the cheese curd may become supersaturated with carbon dioxide.

This combination results in a cheese that cannot withstand the gas pressure and due to structural reasons and/or excess gas production, cracks and splits form.

Multiple factors are believed to be associated with the formation of splits, including: low pH during pressing, non-starter lactic acid bacteria fermentation, anaerobic spore formers, propionic acid bacteria (PAB) with high aspartase activity, low temperature growth of PAB, fermentation of secondary metabolites, loss of texture (rheological properties), and protein hydrolysis.

As of yet, the study noted, there has been no published work on volatile compounds associated with split compared with nonsplit in Swiss cheese.

Selected-ion flow tube mass spectrometry (SIFT-MS) permits the headspace analysis of volatile organic comopounds (VOCs) at concentrations of parts per billion/trillion by volume in real time without the need of volatile preconcentrations.

This study evaluated the applicability of SIFT-MS for the analysis of VOCs in split and nonsplit Swiss cheese samples. The VOC profiles of split compared with nonsplit samples were compared to investigate the formation of splits in Swiss cheese using their organoleptic properties.
A thorough statistical analysis involving statistical analysis system (SAS) and soft independent modeling of class analogy (SIMCA) were done to correlate the results with splits in Swiss-type cheeses.

Two sampling approaches were used to assess the VOC profiles:
Method A: Random samplings of selected 500-pound blocks at cut, manufactured on different days, were obtained from a single factory.
Five pairs of blocks were selected by vat-make. One block was identified as having splits at the time of cutting, the other not. Replication was done by analysis of six sets of shredded cheese subsamples per block of cheese obtained. 60 shredded cheeses were analyzed.

Method B: Fifteen 8- to 10-pound blocks of cheese with splits were acquired from four different factories. Each block was cut into 25-millimeter slices to reveal blind, eye, and split areas. Replication was done by analysis of six sets of shredded cheese subsamples per segment within a block of cheese. 270 cheese samples were analyzed.

Statistical evaluation on the levels of VOCs in split and nonsplits Swiss cheese samples, detected and quantified using the SIFT-MS, has identified that inhomogeneity in the VOC profiles exist both within and between cheese blocks manufactured at the same factory.

Such variability extends to Swiss cheeses between factories as suggested by the varying VOC profile where each factory exhibits a unique set of key compounds that discriminates the split from the blind and eye segments.

One possible cause of this variability, the study said, is fermentation differences brought about by varied milk source, microflora, and other factory-related processing factors and environmental differences that could lead to subsequent disparity in the production of volatile compounds and flavor production in Swiss cheese.

Literature analysis on the biochemical pathways of the key VOCs involved in the differentiation of split against the blind and eye segments suggests that carbon dioxide, released as a by-product along with the production of these VOCs, may contribute to overproduction of gas contributing to the formation of splits and cracks in Swiss cheese stored in the cold room.

VOC profiling of Swiss cheese may be a valuable tool to identify possible solutions to Swiss cheese defects by proposing potential sources (that is, additional carbon dioxide-producing fermentaiton pathways) that need to be closely monitored at the production level in the manufacture of Swiss cheese.