Tackling the future challenges of Organic Animal Husbandry - vTI

! Agriculture and Forestry Research, Special Issue No 362 (Braunschweig, 2012) ISSN 0376-0723
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were taken on the first week of February. Cheeses were manufactured in accordance with the Regulatory
Board of the Zamorano Cheese Denomination of Origin (BOE, 1993). Raw milk (150 L), not
standardized, was incubated with 5.78 mg L -1 direct-vat-set starters made of Streptococcus lactis,
Strep. cremoris and Strep. diacetilactis, (MA400, Choozit, Danisco, Sassenage, France) at 32 ºC.
After 30 min at 32 ºC, when the pH was 6.5-6.6, 0.30 ml L -1 calf rennet (1:150,000 strength) was
added to each vat. Coagulation was allowed to take place over 50 min. When the coagulum had
developed the desired firmness, evaluated subjectively, the curds were cut with a cheese harp until
pieces similar in size to a grain of rice were obtained. Then, the curd was stirred and heated for 25
min at 36 ºC until it had reached the desired consistency to improve its drainage with sieves. The
curd was packed in round hoops (2.5 kg) and pressed for 6 h, starting at1.5 kg cm –2 up to 4 kg cm –2
at 15 ºC. After pressing, the cheeses were salted by soaking them in sodium chloride brine (11º
Baumé) at 15ºC for 24 hours. The cheeses were then moved to a drying chamber where temperature
(11ºC) and relative humidity (82-87%) were controlled. After two months the cheeses were moved
to another chamber at 5-7ºC and 80-85% RH. For each manufacturing process, two cheeses were
removed from each vat for analysis at 0, 1, 2, and 3 months of ripening.
Cheeses were analysed for pH (potentiometric method, CRISON Basic20), fat (Van Gulik method,
ISO 1975), moisture (IDF, 1982), ash (AOAC, 2000) and fat acidity (IDF, 1969). To determine the
instrumental texture six rectangular parallelepipeds, 1 x 1-cm thick and 3 cm long, were obtained
from a slice from the central diameter of each cheese wheel. A TX-T2iplus equipped with a Warner-Bratzler
probe (Stable Micro Systems, Surrey, England) was used to determine the instrumental
texture. The crosshead speed was 1 mm/s and the maximum peak force necessary to cut each parallelepiped
transversally and completely was recorded (WBSF). Cheese colour was measured with a
MiniScan XEPlus on the central slice and CIELab parameters were calculated for the CIE illuminant
D65 and 10º standard observer conditions. The parameters calculated were lightness (L*), redness
(a*) and yellowness (b*) (C.I.E., 1976). Data were analysed by one-way analysis of variance
(ANOVA) (1995 Manugistics, Inc.).
Results
Regarding the physico-chemical parameters (Table 1), the results revealed statistically significant
differences in freshly elaborated cheeses for pH, dry extract and fat acidity. However, at the end of
the ripening process the differences were statistically significant only for fat acidity and ash. The
lower pH of organic cheese is agreement with the lower pH observed for the milk (Revilla et al.,
2009). The evolution of the cheese showed an initial decrease in the pH up to the second month,
due to the conversion of lactose into lactic acid by acidolactic bacteria during the first 30 days of
ripening (Upreti et al., 2006). After proteolysis, these release neutral and basic groups moities (Sousa
et al, 2001), which leads to an increase in the pH. A more intense proteolysis in organic cheeses
would explain why the differences began to decrease until they disappeared. Regarding the dry extracts,
the absence of differences for fat, lactose and protein contents observed between organic and
conventional ewe’s milk (Revilla et al., 2009) shows that the lower value of this parameter observed
in freshly elaborated organic cheeses could be attributed to the lower pH of these cheeses that favoured
the syneresis process (Vivar et al., 2008). The differences disappeared up to the second
month of ripening because the drying conditions were identical. Finally, fat acidity was significantly
higher in organic cheeses than in conventional ones. This parameter is related to higher levels of
free fatty acids and hence with a more intense lipolytic activity (Bachman et al., 1988). In addition,
the differences between both production systems increased with the ripening time. Finally, the ash
content did not show significant differences in freshly elaborated cheeses, in agreement with the
composition of the milk. However, the ash levels were significantly higher in organic cheeses up to
the second month of ripening, which could be due to a more intense proteolysis, as pointed out previously,
which would have produced a higher mineralization of the samples.
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