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. 2019 Nov 1;29(4):459–467. doi: 10.1007/s10068-019-00682-w

Effect of ripening time on bacteriological and physicochemical goat milk cheese characteristics

Rodrigo V Moreira 1, Marion P Costa 2, Beatriz S Frasao 1, Vivian S Sobral 1, Claudius C Cabral 1, Bruna L Rodrigues 1, Sérgio B Mano 1, Carlos A Conte-Junior 1,3,✉
PMCID: PMC7142192  PMID: 32296556

Abstract

Cheese ripening involves lactose metabolism, lipolysis and proteolysis, which are affected by many factors. The aim of this study was to assess changes due to ripening (90 days) of goat milk cheese through bacteriological and physicochemical analysis in order to verify if, at the end of ripening period, this cheese could be considered “lactose-free”. Three batches of the goat milk cheese were manufactured and ripened at 10 °C and 80% relative humidity for 90 days. Titratable acidity increased by about 59 °D due to carbohydrate degradation and organic acid production. However, pH (5.31–5.25) remained constant. Lactococcus was the dominant cheese microbiota, acting in the fermentation of lactose (1.17–0.06 mg/g) and lactic acid production (5.49–s10.01 mg/g). Thus, ripening time was decisive for bacteriological and physicochemical goat milk cheese characteristics.

Electronic supplementary material

The online version of this article (10.1007/s10068-019-00682-w) contains supplementary material, which is available to authorized users.

Keywords: Growth modeling, Lactose-free, Lactic acid, Lactococcus, Organic acids

Introduction

In Brazil, goat milk production, mainly produced by small producers, increased from 15.0 t in 2012 to 15.3 t in 2013 (FAO, 2016). This increase in goat milk production favored the caprine dairy production chain through goat milk cheese manufacturing. Moreover, goat milk is an alternative to cow milk for cheese manufacturing (Costa et al., 2013). Thus, goat milk cheeses present an essential value in the goat dairy industry economy. In general, cheese microbiota is classified into two main groups: Starting lactic acid bacteria (LAB), such as Lactococcus, which contribute to the production of organic acids during the cheese manufacturing process by lactose fermentation, which reduces cheese lactose content and creates a favorable environment for redox potential, pH, and moisture. Therefore, the main function of Lactococcus lactis is to produce enough lactic acid, which can reduce the cheese ripening time (García et al., 2016).

Cheese ripening is a complex set of biochemical events that involves residual lactose, lactate and citrate metabolisms, as well as lipolysis and proteolysis, resulting in characteristic flavor and texture characteristic of the different cheese varieties. These pathways are affected by many factors, including type of milk, type and amount of coagulant and use of starter cultures (McSweeney and Sousa, 2000). Carbohydrate fermentation provides organic acids, which modify the chemical composition of the product, as well as its sensory characteristics. In addition, it is nutritionally favorable for lactose intolerant individuals, since a significant reduction in the levels of these carbohydrates is observed (Costa and Conte-Junior, 2015).

However, no international legal definition for the terms ‘‘lactose-free” or ‘‘lactose-reduced” is available, except for infant and follow-on formulas, in which lactose should be less or equal to 10 mg/100 kcal (Commission Directive, 2006). Some EU Member States have set thresholds at the national level for the use of the terms ‘‘lactose-free”, ‘‘very low lactose” and ‘‘low lactose” for foodstuffs other than products intended for infants. These threshold levels vary from 0.01 to 0.10 g/100 g of final product (EFSA, 1777). In Brazil, the RDC 135/2017 (ANVISA, 2017) establishes parameters for foods presenting lactose restriction, where food considered “lactose-free” should contain a maximum amount of 1 mg/g or mg/L, while “low lactose” products may present values between 1 and 100 mg/g or mg/L (ANVISA, 2017).

Moreover, the organic acid profile present in different cheeses can vary based on the manufacturing process and cheese starter culture (Costa and Conte-Junior, 2015). On the other hand, cheese oxidation reactions are not significant, due to low redox potential. However, lipolysis and fatty acid catabolism present relatively higher importance in cheeses containing moderate to high levels of free fatty acids (Delgado et al., 2011). In this context, this study aimed to assess the effect of ripening time on the bacteriological characteristics, lipid oxidation and carbohydrate metabolism with the production of organic acids and their influence on goat milk cheese characteristics. In addition, the study also investigated if, at the end of the ripening period, the assessed cheese is considered “lactose-free”.

Materials and methods

Goat milk samples

Goat milk samples from one hundred Saanen goats were obtained from a dairy industry (Queijaria Rancho dos Sonhos) located in the interior of the state of Rio de Janeiro, an Atlantic Rainforest region in southeastern Brazil. The goats were healthy and raised in a semi-intensive system receiving bulky and concentrated food in the afternoon, a common process in the region.

The goat milk samples were evaluated regarding titratable acidity, fat content, density at 15 °C (g/mL) and cryoscopic Index (°H), according to the Association of Official Analytical Chemists (AOAC, 2012). pH was determined using a digital pH meter (Model PG1800, Cap Lab, SP, Brazil). Carbohydrates (lactose, galactose, and glucose) and organic acids (lactic, citric and formic) were also assessed (Costa et al., 2016). All analyses were performed in triplicate.

Regarding bacteriological analyses, Enterobacteriaceae, Enterococcus, lactic acid bacteria (LAB), Mesophiles, coagulase positive Staphylococcus and Salmonella (APHA, 2001) were determined. Colony forming units were counted and expressed as log CFU/g. Coliforms at 45 °C and Coliforms 30 °C were also analyzed and expressed as Most Probable Number (MPN).

Cheese manufacturing process

Three goat milk cheese replicates were manufactured (n = 3) at the Queijaria Rancho dos Sonhos dairy industry. A commercial mesophilic starter culture composed by Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris (CHR Hansen R 704; Chr. Hansen, Valinhos, Brazil) was added to pasteurized milk at 32 °C and, after 2 h, 30 mL of commercial liquid rennet (Ha La; Chr. Hansen, Valinhos, Brazil) were added. After 60 min, the curd was cut in 1 cm3 cubes and the curd was stirred continuously at 32 °C for about 2 h before draining off some of the whey. The curd was then salted, placed in cylindrical molds and pressed. Finally, the cheeses were transferred to a drying room where they remained at 10 °C and 80% relative humidity for 90 days.

Milk and 0-, 5-, 10-, 15-, 20-, 30-, 40-, 50-, 70-, and 90-day-old cheese samples were taken from each replicate. Each sample was made up one of whole cheese piece (0.8 kg). All samples were transported to the laboratory chilled (5 °C) and then stored below freezing (− 20 °C), except when the analyses required fresh samples.

Physicochemical analyses

Moisture, ash, protein, fat, titratable acidity and pH contents were determined on day 0 and 90, according to the Association of Official Analytical Chemists (AOAC, 2012). Lipid oxidation was measured as 2-thiobarbituric acid reactive substances (TBARS) (Monteiro et al., 2012). Titratable acidity, pH, and lipid oxidation were determined during ripening (0, 5, 10, 15, 20, 30, 40, 50, 70, and 90-days). All physicochemical analyses were performed in triplicate.

Bacteriological analyses

Lactic acid bacteria, Enterobacteriaceae and Enterococcus bacteria were estimated in goat cheese (FIL-IDF, 1992). LAB were determined on two different media: LAB on MRS agar after incubation at 37 °C for 48–72 h, and Lactococcus on M17 agar after incubation at 30 °C for 18–24 h. Enterobacteriaceae and Enterococcus were enumerated on Violet-Red-Bile-Glucose (VRBG-agar, Merck) and Slanetz–Bartley (m-Enterococcus) agar, respectively, after incubation at 37 °C for 48 h. Colony forming units were counted and expressed as log CFU/g.

HPLC analysis

Carbohydrates (lactose, galactose, and glucose) and organic acids (lactic, formic, citric and acetic) from goat cheese were extracted following the method described by Costa et al., (2016), with adaptations.

Statistical analyses

Enterococcus growth curves were modeled using the DMFit 2.0 (IFR, Norwich, UK) statistical program based on predictive microbiology, according to Baranyi and Roberts (1994). An ANOVA test was used to examine the data obtained for microbiological and physicochemical analyses, which are reported as means (± standard deviations). All ANOVA results were subjected to Tukey’s test at p < 0.05. A principal component analysis (PCA) was also performed to identify clustering. All analyses were carried out using the XLSTAT version 2013.2.03 software (Addinsoft, Paris, France).

Results and discussion

Milk samples

Goat milk chemical parameters were determined as follows: fat 3.56 ± 0.27 (g/100 g milk), density at 15 °C 1.031 ± 0.01 (g/mL), cryoscopic index − 0.576 ± 0.02 (°H), titratable acidity 16.0 ± 0.31 (°D) and pH 6.7. These values are in accordance with Park et al. (2007) and Costa et al. (2013). Carbohydrate content mostly consisted of lactose (58.920 ± 1.042 mg/g), also presenting glucose (0.330 ± 0.014 mg/g) and galactose (0.111 ± 0.027 mg/g). Regarding organic acids, citric acid was present in higher amount (3.990 ± 0.016 mg/g), followed by lactic acid (0.581 ± 0.026 mg/g), and formic acid (0.253 ± 0.009 mg/g). Citric acid is considered the predominant organic acid in milk, present in the form of citrate. During storage, citric acid quickly disappears as a result of bacterial growth. Meanwhile, lactic and acetic acids are lactose degradation products (Costa and Conte-Junior, 2017). These data are similar to those reported by Costa et al. (2016).

Concerning the bacterial analyses, goat milk presented detectable mesophiles (7.46 ± 0.23 Log CFU/g), coliforms 30 °C (> 1.100 NMP) and coagulase positive Staphylococcus (3.62 ± 0.32 Log CFU/g) and negative Enterobacteriaceae, Enterococcus, LAB, Coliforms 45 °C and Salmonella counts, in accordance to the current legislation concerning goat milk (BRAZIL, 2000).

Chemical cheese composition

The goat milk cheese chemical of at the beginning and end of the maturation period (0 and 90 days) are summarized in Table 1. Moisture content decreased during the first days of ripening, which is expected. Moisture decreases are due to the acid development that occurs during ripening and microbial multiplication, resulting in cheese syneresis. Reduced casein hydration may be another contributing fact to moisture decrease, since the pH reaches the isoelectric point of casein. Similar moisture behavior was identified by García et al. (2016) during goat cheese ripening for 75 days. In addition, fat content also decreases during ripening. In this case, the decrease may be associated with the smaller size of goat milk fat globules which are, therefore, more susceptible to the ripening process (Skeie, 2014).

Table 1.

Chemical goat milk cheese composition at the beginning and end of the ripening time

Day Chemical composition (%)
Moisture Ash Protein Fat
0 42.29 ± 0.03b 6.89 ± 0.00a 24.41 ± 0.02a 24.50 ± 0.04b
90 28.15 ± 0.01a 7.51 ± 0.01a 23.02 ± 0.01a 19.11 ± 0.01a
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Values were expressed as mean ± standard deviation

a,bDifferent lower-case letters in the same column represent significant differences (p < 0.05); n = 3

Protein, results were constant during ripening, probably due to limited secondary proteolysis, which may have been influenced by the applied milk heat treatment (Miloradovic et al., 2016). The starter culture type also affects cheese proteolysis. Tabet et al. (2016) have been reported that Lactococcus, as L. lactis subsp. lactis strains displayed acidification activity, but not proteolytic activity. These results agree with those reported by Kondyli et al. (2016) for white-brined goat milk cheese matured for 180 days.

Ash content also remained constant at the end of the cheese maturation period (Table 1). The cheese salt content could have contributed to this behavior throughout the ripening period. In addition, constant pH values associated with low casein micelle demineralization may have also contributed to ash value maintenance. Sert et al. (2014) reported similar values at the end of ripening.

pH and titratable acidity

The pH and titratable acidity results are displayed in Fig. 1. The pH remained constant during the ripening period, whereas titratable acidity presented a significant increase. These values indicate that the observed pH and lactic acid values, as well as lack of lactose, could be indicators of successful cheese acidification throughout the ripening period, due to lactic microbiota activity (Tabet et al., 2016). Miloradovic et al. (2016) investigated the influence of heat treatment on milk pH, reporting that cheeses submitted to heat treatment at 65 °C for 30 min did not undergo pH decreases. These authors postulate that this lower heat treatment could reduce protein matrix permeability to rennet and microorganism activities. In addition, associated casein and phosphate systems are also known to interfere in the hydrogenation potential of goat milk cheese (Skeie, 2014). pH also indirectly affects cheese texture, by altering the activity of enzymes necessary for ripening. Increases in pH markedly alter cheese rheological properties and lead to softer curds (McSweeney, 2004). The fact that the pH remained constant during ripening suggest these microorganisms uptake the organic acids present in the curd and, consequently, allow for the development of ripening bacteria adapted to the curd composition and ripening environment, such as Enterococcus (Spinnler, 2017). Similar behavior was reported by Tabet et al. (2016) for goat milk cheese after 90 days of ripening.

Fig. 1.

Fig. 1

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Changes in pH and titratable acidity values of goat milk cheese under storage at 5 °C during ripening (90 days)

A significant increase in titratable acidity (59 °D) was observed, related to lactose fermentation by lactic microbiota leading to the production of organic acids (Costa and Conte-Junior, 2015), noted as an increase in lactic acid values until the end of the ripening period. Titratable acidity may also be influenced by the release of amino acids and free fatty acids after proteolysis and lipolysis, respectively. Cheese acidity is of paramount importance, since it is directly related to the predominant microbiota and biochemical reactions in the product.

Lipid oxidation

Goat milk cheese TBARs values during ripening (90 days) are presented in Fig. 2. TBARS results remained constant throughout the ripening period. TBARs levels are essential in cheese, since they allows for lipid oxidation assessments, which is influenced by other factors, such as the fatty acid profile of the initial milk sample and protective effects against lipid oxidation (Boutoial et al., 2013). Skeie (2014) reported that a rancid flavor is strongly correlated to the free fatty acid (FFA) content in milk, with short and medium-chain fatty acids (FA) reported as predominant in goat milk. However, Atasoy and Türkoǧlu (2009) reported that milk pasteurization reduces lipolysis levels and the amounts of available FFA throughout cheese ripening. Therefore, lipid oxidation is not a significant process in several cheeses (Delgado et al., 2011), probably due to the presence of natural milk antioxidants and a low redox potential.

Fig. 2.

Fig. 2

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Changes in TBARS values of goat milk cheese under storage at 5 °C during ripening (90 days)

Similar behaviors were found by Boutoial et al. (2013) for fresh goat milk cheese, while Delgado et al. (2011) reported an increase in malondialdehyde (MDA) during 30 days of raw goat milk cheese ripening.

Bacterial analyses

The evolution of the different microbial groups throughout the cheese ripening period (0-90 days) is presented in Table 2. Lactic acid bacteria (LAB), represented by the starter culture, and nonstarter lactic acid bacteria (NSLAB) were the predominant microbial groups.

Table 2.

Goat milk cheese bacterial counts (Log CFU/g) during ripening at 5 °C

Days Lactococcus LAB Enterobacteriaceae
0 8.49 ± 0.39b 8.97 ± 0.18c 4.58 ± 0.77a
5 8.28 ± 0.48ab 8.86 ± 0.45cb 4.76 ± 0.98a
10 8.24 ± 0.36ab 8.37 ± 0.33c 4.53 ± 1.11a
15 7.99 ± 0.64ab 8.30 ± 0.32c 4.09 ± 1.23a
20 8.05 ± 0.52ab 8.22 ± 0.09abc 4.42 ± 0.82a
30 8.00 ± 0.37ab 8.10 ± 0.10abc 4.78 ± 0.57a
40 7.80 ± 0.39ab 7.87 ± 0.03abc 4.79 ± 0.00a
50 7.31 ± 0.67ab 7.78 ± 0.18abc 3.66 ± 0.57a
70 7.06 ± 0.18ab 7.23 ± 0.54a 3.96 ± 0.64a
90 6.91 ± 0.40a 7.35 ± 0.40ab 4.09 ± 0.83a
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LAB Lactic acid bacteria

Values were expressed as mean ± standard deviation

a,bDifferent lower-case letters in the same column represent significant differences (p < 0.05); n = 3

Lactococcus was the predominant microbiota among lactic acid bacteria during cheese ripening. LAB and Lactococcus were present at the highest content on day 0 (8.97 ± 0.18 and 8.49 ± 0.39 Log CFU/g, respectively) and decrease at the end of ripening period (7.35 ± 0.40 and 6.91 ± 0.40 Log CFU/g, respectively). This may be a consequence of competition with other microbial groups, such as Enterococcus. The LAB group, mainly Lactococcus, contributes to the development of cheese biochemical, microbiological and sensorial characteristics.

Concerning Enterobacteriaceae counts, values remained constant throughout the ripening period (Table 2), indicating that, Enterobacteriaceae were not influenced by maturation time. This may be associated with certain inhibitory factors, such as high LAB concentrations and cheese acidity increases. The same behavior was reported by Oliszewski et al. (2013) during goat milk cheese ripening.

Growth modeling

Changes in Enterococcus counts during ripening are displayed in Fig. 3. The initial count was of 4.71 ± 0.20 Log CFU/g, increasing at the end of ripening period (6.02 ± 0.20 Log CFU/g). Enterococcus in goat milk is considered an indicator of inadequate sanitary conditions during milk and cheese production and processing or of the equipment and utensils used during processing (Oliszewski et al., 2013; Tabet et al., 2016). On the other hand, the persistence and increased counts of this microorganism during ripening have been attributed to its range of growth temperatures, high heat and salt tolerance and its ability to produce bacteriocins, which lead to better chances to compete and outweigh other microorganisms (Tabet et al., 2016).

Fig. 3.

Fig. 3

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Enterococcus counts during goat milk cheese ripening (90 days) at 5 °C

The highest Enterococcus recovery in these cheeses also corroborates Lactococcus growth difficulties after 50 days. It has been well-established that Enterococcus contribute to cheese aroma and flavor development, due to its proteolytic and lipolytic activities, and that it represents a considerable microbiota proportion in traditional cheeses produced with raw or pasteurized milk (Tabet et al., 2016).

Enterococcus growth parameters were determined as a 42.85 lag phase (days), 4.49 log phase (hours), and 6.02 number of colonies (log CFU/g) in the stationary phase. The lag phase was extensive, demonstrating difficulty in adapting to cheese ripening conditions. Microbial dynamics in cheese depend on several factors, such as milk composition, starter culture, rennet addition, salting, temperature, relative humidity (85–97%), pH, water activity, redox potential and moisture. In the present study, the high moisture content and lower acidity at the beginning of the maturation period (Table 1), as well as the competitiveness and inhibition provided by the starter culture, may have been determinant for the extensive lag Enterococcus phase (Guerzoni et al., 1999). Therefore, the characteristics and modifications observed during cheese ripening led to a longer adaptation period for this microorganism, extending the lag phase and, consequently, product shelf-life.

The generation time was short (log phase), indicating high growth rates with microorganism adaptation. Proteolytic and lipolytic activities during ripening may be either an indirect effect, leading to a shift of the microbial population (Guerzoni et al., 1999). Moreover, medium acidification favors Enterococcus growth, which is more acid-resistant than Lactococcus. The generation time was lower than that reported by Mcauley et al. (2015), but similar to their results when comparing Enterococcus growth at 4 °C and 7 °C, where storage at high temperatures led to shorter generation times.

Despite the high Enterococcus growth rate, indicating high growth rates with microorganism adaptation, this microorganism group reached the stationary phase before the end of the maturation period. The maximum viable count of Enterococcus was of 6.02 ± 0.20 Log CFU/g, lower than the valued reported by Mcauley et al. (2015), indicating that the cheese ripening conditions were able to contain microbial growth and lower cell counts during the stationary phase.

Carbohydrates and organic acids

Carbohydrate and organic acid contents in goat milk cheese during the ripening period are displayed in Table 3. Lactose contents decreased throughout the ripening period (about 1.11 mg/g), attributed to lactic microbiota growth, especially Lactococcus. In matured dairy products, lactose is metabolized by lactic acid bacteria during ripening, releasing glucose and galactose and synthesizing organic acids as byproducts (Bezerra et al., 2017; Costa and Conte-Junior, 2015). As a result, ripened cheese contains low lactose content. Therefore, the produced goat milk cheese can be considered “lactose-free”, and could be safely added to the diet of consumers presented lactose intolerance.

Table 3.

Carbohydrates and organic acids values (mean ± standard deviation) in mg/g in goat milk cheese during ripening at 5 °C

Parameter Ripening time (days)
0 5 10 15 20 30 40 50 70 90
Lactose 1.17 ± 0.09f 1.00 ± 0.05f 0.88 ± 0.05e 0.87 ± 0.04e 0.83 ± 0.04d,e 0.79 ± 0.07d 0.68 ± 0.11b,d 0.63 ± 0.03b,c 0.51 ± 0.05b 0.06 ± 0.07a
Glucose 0.03 ± 0.01a 0.05 ± 0.02a 0.03 ± 0.01a 0.04 ± 0.01a 0.03 ± 0.02a 0.03 ± 0.01a 0.02 ± 0.01a 0.03 ± 0.01a 0.03 ± 0.01a 0.01 ± 0.01a
Galactose 0.04 ± 0.01a 0.06 ± 0.03a 0.09 ± 0.01a 0.14 ± 0.01b 0.18 ± 0.01b,c 0.18 ± 0.01c 0.19 ± 0.01c 0.30 ± 0.01d 0.32 ± 0.01d,e 0.36 ± 0.01e
Citric acid 0.86 ± 0.06d,e 0.81 ± 0.07d,e 0.73 ± 0.02b 0.57 ± 0.02a 0.70 ± 0.05b 0.82 ± 0.02c,d 0.88 ± 0.13 0.81 ± 0.01c 0.69 ± 0.13b 0.93 ± 0.20e
Lactic acid 5.49 ± 0.11a 5.96 ± 0.11a,b 7.01 ± 0.33b 7.80 ± 0.43c 8.36 ± 0.26d 8.89 ± 0.88e 8.70 ± 0.14f 8.97 ± 0.39 g 9.03 ± 0.49 h 10.01 ± 0.29i
Formic acid 0.17 ± 0.03c 0.15 ± 0.01c 0.14 ± 0.03b,c 0.28 ± 0.01d 0.07 ± 0.04a 0.05 ± 0.04a 0.07 ± 0.12a 0.24 ± 0.02d 0.09 ± 0.31a,b 0.08 ± ±0.01a
Acetic acid 0.60 ± 0.08e 0.53 ± 0.01c 0.50 ± 0.07c 0.56 ± 0.05c 0.09 ± 0.05a 0.12 ± 0.08a 0.37 ± 0.19b 0.53 ± 0.01c,d 0.13 ± 0.63a 1.52 ± 0.05f
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Values were expressed as mean ± standard deviation

a–hDifferent lower-case letters in the same line represent significant differences (p < 0.05); n = 3

On the other hand, significant galactose accumulation is observed during ripening (Table 3), a result of lactose catabolism via β-galactosidase (Costa and Conte-Junior, 2015), explaining the increased galactose values (0.32), in agreement agreed with the study published by Porcellato et al. (2015) for Cheddar cheese. Glucose content remained constant during ripening (Table 3), characterizing lactose hydrolysis production and concomitant consumption by microbiota. This sugar can also be consumed via different pathways, such as the Embden–Meyerhof pathway, which leads to several intermediary products and organic acids, alcohols, and other volatile substances as final products (Bezerra et al., 2017), including the lactic and citric acids found in the present study.

Regarding organic acids, lactic acid presented the highest value (Table 3). This organic acid is the most abundant in all cheeses, resulting from lactose hydrolysis by microbial metabolism (Tofalo et al., 2015). Lactic acid contents increased significantly during cheese ripening, displaying a 4.52 mg/g increase. Dynamic biochemical metabolic processes, especially lactate and citrate, are essential precursors for a series of reactions leading to the production of lactic, acetic, citric and formic acids. Furthermore, several lactic acid bacteria species, as Lactococcus, metabolize carbohydrates into trace amounts of acetic acid, formic acids and ethanol, by the homofermentative metabolic pathway.

Citric, acetic and formic acids contents fluctuated during ripening (Table 3), suggesting their production and consumption by microbial metabolism (Costa and Conte-Junior, 2015). The citric acid fluctuation may be due to volatile compound production by lactic acid bacteria metabolism (Bezerra et al., 2017). Despite this, the increases in citric acid contents at the end of the ripening period may be associated with increased galactose and Enterococcus counts, suggesting that the carbohydrate metabolism contributed to citric acid production. Moreover, according to Tofalo et al. (2015), formic acid can also be formed through direct glucose metabolism.

Acetic acid, on the other hand, originates from carbohydrate hydrolysis mainly by Enterococcus and Enterobacteriaceae, and by different lactic acid bacteria reactions, such as glycolysis and citrate metabolisms and lipolysis. The significant fluctuation observed during ripening most likely resulted from the subsequent use of acetic acid in the formation of other aromatic compounds (Bezerra et al., 2017). Nevertheless, acetic acid presented a substantial increase at day 90, at 1.52 ± 0.05 mg/g. Delgado et al. (2011) also reported higher acetic acid values in other goat milk cheeses.

This study demonstrated that cheese ripening time has direct effects on goat cheese ripening characteristics, related to the development of specific microbiota, predonminantly Lactococcus and Enterococcus. The hydrolysis of certain compounds, such as lactose, and the production of organic acids are essential to characterize these cheeses, which at the end of the ripening period, were characterized as “lactose-free”. In conclusion, the ripening period was critical for characteristic bacteriological and physicochemical goat milk cheese parameters.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 31 kb) (31.6KB, docx)

Acknowledgements

The authors thank the Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (process no. E-26/201.185/2014 and E-26/010.001.911/2015, FAPERJ, Brazil) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (process no. 311361/2013-7, 400136/2014-7 and 166186/2015-5, 439731/2016-0 and 150200/2017-0 CNPq, Brazil). The authors also thank the Rancho dos Sonhos Company.

Compliance with ethical standards

Conflict of interest

The authors declare no conflict of interest.

Human and animal rights

This article does not contain any studies with human or animal subjects performed by any of the authors.

Footnotes

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Contributor Information

Rodrigo V. Moreira, Email: rodrigo.vilela2vet@gmail.com

Marion P. Costa, Email: marioncosta@ufba.br

Beatriz S. Frasao, Email: beatrizfrasao@id.uff.br

Vivian S. Sobral, Email: vivianschwaab@gmail.com

Claudius C. Cabral, Email: ccabral@id.uf.br

Bruna L. Rodrigues, Email: brunalrmlk@yahoo.com.br

Sérgio B. Mano, Email: sergiomano@id.uff.br

Carlos A. Conte-Junior, Email: carlosconte@id.uff.br

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