Impact of Clostridium spp. on cheese characteristics: Microbiology, color, formation of volatile compounds and off-flavors

Occurrence of Clostridium spp. in ewe’s milk: enumeration and identification of isolates

“…Despite the fact that not only bovine milk cheeses but also ewe's milk cheeses can be affected by late-blowing defects (Gómez-Torres et al 2015), little is known regarding the occurrence of clostridial spores in ewe's milk. Indeed, the current literature regarding the presence and relevance of clostridia spores in Italian ewe's milk is limited (Scintu et al 2004).…”

“…Indeed, the current literature regarding the presence and relevance of clostridia spores in Italian ewe's milk is limited (Scintu et al 2004). However, a few surveys carried out in Spain are available (Garde et al 2011;Arias et al 2013;Gómez-Torres et al 2015). Concerning data from reports analyzing milk samples for the production of Manchego cheese in Spain, Garde et al (2011) detected lactate-fermenting clostridial spores in 97% of samples.…”

Volatile compounds associated with desirable flavour and off-flavour generation in ewe´s raw milk commercial cheeses

“…Gross composition of cheese samples was quite similar to that of ripened cheeses made from ewe's milk in other Mediterranean areas [10,28]. Figure 1 shows the percentage of assessors that marked the presence of desirable flavours and off-flavours in the selected commercial cheeses.…”

“…Ketones were the second mayor chemical family in the headspace of ND cheeses being methyl ketones major compounds (Table 2). Butan-2-one and 3-hydroxybutan-2-one are generated from butane-2,3-one in the metabolism of citrate and lactose mainly by lactic acid bacteria [8,10]. These ketones, with milky and sweet odour notes, could be key odourants associated with the ewe's milky desirable flavour of ND cheeses, as other authors reported for different cheese varieties [10-12, 33, 34].…”

“…As other authors reported, an excessive concentration of carboxylic acids, mainly short and medium chain FFA, can lead to a rancid and lipolyzed flavour of cheese [3,8]. As mentioned above, FFA are liberated from cheese fat triglycerides by lipases from different origin during ripening, so FFA concentration increases with time [10,35]. However, RA cheeses were not more ripened than ND cheeses, so excessive lipolysis due to other causes should cause this off-flavour during ripening.…”