Characteristics of Milk, Cheddar-Like and White Cheese Obtained from Three Goat Phenotypes during Three Lactation Periods

Abstract

Goat's milk from three phenotypes: Shami, Local, and Mixed was collected during three lactation periods in 2002. The milk was analyzed for moisture, protein, fat, ash, and lactose content. Also milk was examined for yeast, mold and bacterial content. Cheddar and white cheese were manufactured from goat's bulk milk and examined for chemical composition and evaluated for color, taste and flavor, appearance, and texture and aroma. Results showed that the chemical composition of goat's milk varied significantly during the whole year and also among the three goat phenotypes. Local goats produced milk at the first lactation period with highest (44.6%) fat content: the lowest fat content was 29.8% for the Mixed color phenotype at the end of the year. Protein showed the same trend. Shami goat produced milk lower in lactose and ash content than the mixed color breed, whereas the Local (black) produced milk having intermediate content of lactose and ash. Cheddar and white cheese were highly acceptable. Their composition varied—cheddar cheese was higher in protein and NSF but slightly lower in fat content. White cheese retained more lactose. Goat's milk of Shami, Local (black) and Mixed color phenotypes were found to be highly contaminated with bacteria and mold due to lack of hygiene. Milk contained low number of pathogenic bacteria. Using a pasteurization temperature at 73°C for 16 seconds was found to eliminate them.

Keywords:

• Lactation periods
• Chemical composition
• Microbiological Quality
• Sensory Characteristics
• Cheddar-like cheese
• White Cheese
• Goat phenotypes

INTRODUCTION

The goat's milk production ranks third in the world after bovine and buffalo milk. Dairy goat farming plays an important role in developing countries. Goat's milk provides one of the principle sources of animal protein in many regions, such as the Middle East, Southeast Asia, and some tropical countries. Goat's milk also serves as a good substitute to cow's milk and is often recommended by the medical profession in situations where bovine milk may bring about allergic responses in individual consumers.[1]

Goat is a very well adapted animal to the diverse environmental conditions in Jordan. There are few breeds of goats raised in Jordan, including: the Local goat breed, which is known as Balady; Shami goat which is red in color; and from Syrian origin (also known as Damascus goat); and, the Mixed or colored goat that is a product of crossing between Local and Shami goats or other hybrids. Balady (Local) goat is of Jordanian origin, whereas Shami has been introduced to Jordanian farmers from Syria due to its milk productivity. Goat farming is considered as an important socio-economic activity in Jordan. There are one million heads, mainly Local (black), Shami and their hybrid goat phenotypes. Goats in Jordan are raised for milk, meat, and hair production. Goats are raised in small livestocks. Goat milk is very popular in the Middle East and is consumed as liquid milk or is used to produce the traditional dairy products such as yoghurt, white cheese, labaneh, Jameed, sour milk, kishek, butter, ghee, and others. The goat milk industry is still considered a home industry; the farmer and his family members are usually responsible for feeding, management, animal medical care, hand milking, processing and marketing the products. The demand for meat and milk in the Middle East is increasing annually and is projected at 3.7 and 3.1%, respectively.

Because the goat farmers in Jordan lack the sound knowledge about milk technology, farming systems and management, a program was initiated by our group in order to study the microbial and chemical composition of milk and cheese obtained from three goat breeds, as well as to report on the variation on the chemical composition of goat milk during lactation periods.

MATERIALS AND METHODS

Sampling

Goat milk samples, approximately one liter each, were collected from farms in the Ajloun area once every week during the years 2002–2003 to be tested for chemical composition and microbial content. Samples were transported on ice to the laboratory and kept in refrigerator at 4°C until analysis, which was usually carried out on the same day. Goat's milk samples were collected from three breeds, Shami, Local, and Mixed. All animals were healthy, 3 to 5 years old, and weighing 50–60 kg. Other milk samples were collected from bulk samples to examine the composition of bulk good's milk, as well as to test for cheddar and white cheese manufacturing.

Chemical Analysis

Moisture, fat, protein (N × 6.38), ash, and solid non fat (NSF) of goat's milk samples were determined according to standard procedures outlined by Richardson.[2] Lactose content was calculated by difference. Averages were recorded for each lactation period. Lactation periods were proposed as First semester or lactation period to cover goat's milk collected during the months of January, February, March, and April. The second lactation semester included May, June, July, and August. The third lactation period covered September, October, November, and December. The same procedures were used to analyze white and cheddar cheese made from bulk goat's milk during the same lactation periods.

Microbiological Analysis

Goat's milk samples also were subjected to microbiological analysis to determine TPC (total plate count), yeast, mold, Staphylococci, S. aureus, Streptococci, Enterobacter, E. coli, coliforms, Salmonella and Shigella. Standard procedures were followed as outlined by Vanderzant.[3] The averages of cfu/ml (colony forming unit per ml) were recorded.

Cheddar-like Cheese Manufacturing

Ten kg of goat milk were used to produce around one kg of cheddar cheese. A small water bath and small cheese vat (45 × 40 × 25 cm) were used to represent double jacketed cheese vat. Yoghurt starter, annatto, and rennet enzyme were used, and the cheese was prepared according to the procedure outlined by Kosikowski.[4]

White Cheese Manufacturing

Ten kg of goat's milk were pasteurized at 73°C for 16 seconds, and then cooled to 35°C; rennet was added. Curd was formed after 40 minutes; curd was cut into small cubes and separated from the whey. The curd was pressed overnight. Curd was cut into 4 × 5 cm and covered with dry salt for 24 hours. Cheese cuts were removed from the salt and kept in brine (12% salt). White cheese pieces were subjected to chemical and microbiological analysis.

Trained Sensory Evaluation

An eight-member trained descriptive panel was trained according to the spectrum methodology. The Spectrum method involves scoring perceived intensities with reference to pre-learned scales using standard attribute names with their standards that define a scale of intensity[5] and general acceptability in duplicates. Panelists attended an orientation session in which the panelists were able to narrow down the list of references for each descriptor. The panelists used the orientation session to improve their reproducibility and accuracy. A present score by the panelists for color (20), taste and flavor (30), texture and appearance (25), and aroma (25). Each property was given a score (as shown in parentheses). The panelist was asked to taste the cheese and to give a high score if it was liked and a lower score if it was not liked by the panelist. The intensity scale anchored by references as defined by Spectrum methodology was used in assigning values to the various descriptors.[6]

Statistical Analysis

The collected data were subjected to statistical analysis using MSTATC computer program (MSTATC program, Michigan State University). The averages were compared, and the LSD (least significant difference) between the means were computed according to Steel and Torrie.[7]

RESULTS AND DISCUSSION

The chemical composition of goat's milk varied significantly among Shami, Local, and Mixed phenotypes and lactation periods as shown in Table 1. Data in Table 1 show the chemical composition of pooled milk collected from 6 to 10 goats from each phenotype during each lactation semester. The protein content of Shami goat varied significantly from lactation semester to the other lactation semester during the year. Protein content ranged from 17.3% at the end of lactation to 23.7% for the first four lactation months. It was noticed also that the milk protein and other milk components varied from week to week or from month to month. Milk obtained from Local breed contained higher protein than milk obtained from Shami goat and ranged from 24.6% (first semester) to 20.6% (at the second semester). Protein content was the highest in milk collected from the Mixed breed at the first lactation semester (25.6%). Shami goat was introduced to Jordan due to its high milk productivity. The Local black goat phenotype is known for its low milk production, but it is favored for its meat.

Table 1 Chemical composition of goat milk collected at three lactation periods from Shami, Balady, and Mixed goat phenotypes ^a

Goat breed	Lactation semester	Protein (%)	Fat (%)	Lactose (%)	Ash (%)
	1	23.7 ^a∗	44.3 ^a	26.0^c	5.2^c
Shami (red)	2	18.3^cd	39.8^ab	35.6^b	5.0^c
	3	17.3^d	35.1^bc	34.9^b	5.5^bc
	1	24.6 ^a	44.6 ^a	25.9^c	5.0^c
Local (black)	2	20.6^bc	44.5 ^a	34.4^b	5.5^bc
	3	22.7^ab	35.0^bc	40.5 ^a	6.0^ab
	1	25.6 ^a	35.3^bc	34.1^b	5.2^c
Mixed (colored)	2	17.6^cd	34.4^bc	41.6 ^a	6.4 ^a
	3	18.9^cd	29.8^c	44.9 ^a	6.4 ^a
LSD P < 0.05		3.1	5.8	4.7	0.7
^a = Data are average of 16 samples collected through four months as a sample per week and computed on dry weight basis. ∗Means in columns followed by the same letter are not significantly different according to LSD.

Fat content as presented in Table 1 varied significantly and ranged from 44.6% for the first lactation semester for Local breed to 29.8% for the third lactation semester of the Mixed goat breed. Lactose content also varied significantly and ranged from 44.9% for third semester of Mixed breed to 25.9% for milk obtained from Local breed at the first semester. Sung[8] reported that the major milk components varied significantly among goat breeds (Alpine, Nubian, Saanen, and Toggenburg). Data on protein, fat, and lactose shown in Table 1 are in agreement with similar values reported by earlier work.[9,8,10]

Goat flocks raised by Jordanian farmers involve a mixture of Local, Shami, and Mixed phenotypes. Farmers pool the milk collected from the whole flock and either sell or process it into traditional (Laban, Labaneh, white cheese, Jameed, butter milk, butter, ghee, and kishek) dairy products. These products are marketable. A sample from bulk milk was drawn every week during three lactation periods to be tested for chemical composition. Another sample was taken to produce cheddar cheese and to examine its chemical composition. Table 2 shows the data on bulk milk chemical composition. Fat, protein, ash, lactose, and nonsolid fat contents were found to vary significantly during lactation periods. Protein content of bulk milk was found to be the highest during the second semester (20.5%) and lowest during the first semester (19.1%). Fat contents also varied significantly (P ≤ 0.05) and were found to be the highest (35.8%) during the third lactation semester and lowest during the second semester (32.3%). Ash content did not show significant variation during the one year lactation period. Ash content ranged from 6.3 to 5.6% as shown in Table 2. These data are in agreement with data reported on goat and cow's milk composition reported by Hadjipanayiotou.[11]

Table 2 Chemical composition of goat milk collected at three lactation periods ^a

Lactation semester	NSF (%)	Ash (%)	Lactose (%)	Protein (%)	Fat (%)
First semester	63.1^b∗	5.6 ^a	38.4^b	19.1^b	37.0 ^a∗
Second semester	67.7 ^a	6.3 ^a	41.0 ^a	20.5 ^a	32.3^b
Third semester	64.2^b	6.2 ^a	38.8^b	19.3^ab	35.8 ^a
LSD P < 0.05	2.9	1.6	2.2	1.3	2.9
^a = Data are average of 16 samples collected through four months as a sample per week and computed on dry weight basis. ∗Means in columns followed by the same letter are not significantly different according to LSD.

Lactose and SNF varied significantly (P ≤ 0.05), and the highest values for lactose and NSF are reported for the second lactation period (41 and 67.7%, respectively) as shown in Table 2. The major components of goat milk varied significantly during the lactation periods. It is obvious that the protein, fat, lactose, and ash content of milk are influenced by several factors such as breed,[12] nutrition, animal health, management, and environment. Jordanian goat farmers follow the open system because goat industry is expensive to farmers who reley on free grazing.

The data on chemical composition of cheddar cheese made from bulk goat's milk are presented in Table 3. Differences in protein, fat, ash, lactose, and NSF content are shown in Table 3, were not statistically different (P ≤ 0.05) during the lactation periods. As shown in Table 3, the chemical composition of cheese varied but not significantly as affected by lactation period. Those data are in agreement with similar data reported by Fresno[1] on Spanish goat's milk cheese (Armada variety).

Table 3 Chemical composition of cheddar cheese made from bulk goat milk collected at three lactation periods ^a

Lactation semester	Protein (%)	Fat (%)	Ash (%)	Lactose (%)	NSF (%)
First semester	38.7 ^a∗	35.0 ^a	10.5 ^a	15.8 ^a	65.0 ^a
Second semester	37.2 ^a	38.6 ^a	10.2^b	14.1 ^a	65.1 ^a
Third semester	38.0 ^a	36.9 ^a	10.3^ab	14.9 ^a	63.2 ^a
LSD P < 0.05	1.8	10.1	0.3	10.0	11.5
^a = Data are average of 16 samples collected through four months as a sample per week and computed on dry weight basis. ∗Means in columns followed by the same letter are not significantly different according to LSD.

Table 4 shows the data on sensory evaluation. As expected, cheddar cheese made from bulk goat's milk during three lactation periods did not differ significantly in color, appearance, taste and texture, or aroma. The total scores ranged from 68.2% (third semester) to 76.8% (first semester). Panelists are very familiar with the white cheese, but not the cheddar, which might explain the non significant variation in sensory evaluation of cheese characteristics. The goat cheddar cheese was acceptable during the three milking periods and scored higher than 75%, except for the third lactation semester (68%).

Table 4 Sensory characteristic of cheddar cheese made from bulk goat milk collected at three lactation periods (data average of 16 samples and computed on dry weight basis) ^a

Lactation semester	Color ( 20)	Appearance (15)	Taste (30)	Texture (15)	Aroma (20)	Total (100)
First semester	17.8 ^a∗	10.5 ^a	23.4 ^a	10.8 ^a	14.3 ^a	76.8 ^a
Second semester	18.6 ^a	12.0 ^a	22.2 ^a	8.3 ^a	15.0 ^a	76.0 ^a
Third semester	14.3 ^a	8.3 ^a	21.3 ^a	9.3 ^a	14.8 ^a	68.2 ^a
LSD P < 0.05	5.3	5.8	9.3	4.0	5.3	23.4
^a = Data are average of 16 samples collected through four months as a sample per week and computed on dry weight basis. ∗Values in columns followed by the same letter are not significantly different according to LSD.

The chemical composition of white cheese made from bulk goat milk is presented in Table 5. Data show no significant variation for all major bulk milk components, except for ash content which varied significantly during the whole lactation period. Cheese quality is influenced by two important factors: milk composition and the effect of ripening, according to Boyazoglu and Morand-Fehr.[13] The values reported in this investigation on cheese chemical composition are in agreement with similar values reported by earlier work.[14,15,16] Haenleina[15] reported the gross analysis of twenty type of cheeses, the Gjetost cheese of Norway, which is made from goat milk has 13.4% moisture, 42.6% lactose, 29.5%fat, 9.6% protein, and 4.8% ash.

Table 5 Chemical composition of white cheese made from bulk goat milk collected at three lactation periods ^a

Lactation semester	Protein (%)	Fat (%)	Ash (%)	Lactose (%)	NSF (%)
First semester	25.6 ^a∗	39.6 ^a	9.4 ^a	25.4 ^a	60.1 ^a
Second semester	26.1 ^a	43.3 ^a	9.6^b	20.7 ^a	56.2 ^a
Third semester	26.0 ^a	41.6 ^a	9.6^ab	23.0 ^a	58.5 ^a
LSD P < 0.05	0.6	4.1	0.3	5.8	4.1
^a = Data are average of 16 samples collected through four months as a sample per week and computed on dry weight basis. ∗Means in columns followed by the same letter are not significantly different according to LSD.

Data on microbiological examination of goat milk are shown in Table 6. TPC ranged from 1.3 × 10⁵ to 4.1 × 10⁵ cfu/ml. Yeast count ranged from 3.1 × 10³ (milk obtained from Mixed breed) to 7.9 × 10⁵ cfu/ml (milk obtained from Shami goat). Mold count was also high and ranged from 1.7 × 10³ to 8.7 × 10³ cfu/ml. Staphylococci was found to range from 6.4 × 10³ to 3.5 × 10³ cfu/ml (in Mixed goat breed milk during the second lactation semester). S. aureus was reported only once during the whole year at the first lactation period of the Mixed colored goat breed (three colonies were identified). Streptoccoci bacteria were found in the milk of the three breeds all the year around ranging from 10³ (first lactation period of the Mixed color breed) to 5.4 × 10³ cfu/ml (milk of the Local black milk at the second lactation semester), as shown in Table 6.

Table 6 Microbiological analysis of milk obtained from three goat breeds during three lactation periods ^a

Goat breed	Lactation semester	TPC	Yeasts	Molds	Staphylococcus	S. aeureus	Streptoccocus	Enterobacteriacea	E. coli	Coliforms	Salmonella	Shigella
	1	1.7 × 10^5	3.3 × 10^4	nd	2.0 × 10^3	−	1.7 × 10^3	6.9 × 10^4	−	nd∗	−	–
Shami	2	4.1 × 10^5	7.9 × 10^5	1.4 × 10^3	1.9 × 10^3	−	4.8 × 10^3	2.8 × 10^6	−	3.6 × 10^2	−	–
	3	2.7 × 10^5	6.4 × 10^5	3.7 × 10^3	3.5 × 10^3	−	2.8 × 10^3	6.5 × 10^2	−	5.2 × 10^1	−	–
	1	1.9 × 10^5	4.4 × 10^4	9.1	2.3 × 10^3	−	4.4 × 10^3	7.3 × 10^4	+	nd	+	–
Local	2	2.2 × 10^5	5.2 × 10^5	4.2 × 10^3	2.2 × 10^3	−	5.4 × 10^3	3.6 × 10^4	+	1.2 × 10^2	–	–
	3	1.3 × 10^5	1.2 × 10^5	8.7 × 10^3	2.8 × 10^3	−	2.8 × 10^3	6.5 × 10^3	+	9.3 × 10^1	–	–
	1	3.8 × 10^5	3.1 × 10^3	9.1	1.6 × 10^3	+	1.0 × 10^3	2.4 × 10^4	−	nd	–	–
Mixed	2	4.7 × 10^4	1.4 × 10^5	nd	6.4 × 10^2	−	1.2 × 10^3	Nd	−	nd	–	–
	3	2.0 × 10^5	1.6 × 10^5	7.5 × 10^3	2.8 × 10^3	–	5.2 × 10^3	7.2 × 10^3	+	9.4 × 10^1	–	–
^a = Data are average of 16 samples collected through four months as a sample per week; nd = not detected.

Psoni[17] also investigated the microorganisms in traditional Greek cheese prepared from raw goat milk, and reported the occurrence of Enterobacteriaceae, Coliforms, Staphylococci, lactic acid bacteria, Enterococci, and Yeast. The number of these organisms found were reduced as storage temperature is reduced from 15°C to 4°C. The values reported in this investigation (Table 7) were lower than the mean values reported by Psoni.[17]

Table 7 Microbiological examination of cheddar cheese ^a

Lactation semester	TPC	Yeasts	Molds	Streptococci
First semester	4 × 10^4	5 × 10^4	–∗	2 × 10^4
Second semester	3 × 10^4	7 × 10^4	–	1 × 10^4
Third Semester	6 × 10^4	5 × 10^4	–	1 × 10^4
^a = Data are average of 16 samples collected through four months as a sample per week; ∗– = not detected.

CONCLUSION

In conclusion, the results of the current investigation showed that the chemical composition of milk obtained from Shami, Local, and Mixed goat phenotypes varied significantly (P ≤ 0.05) during the whole year. It has been found that the milk of the three phenotypes produced acceptable cheddar-like cheese. Also the milk of the three phenotypes was found to contain a very low number of pathogens and highly contaminated with bacteria, but within the acceptable range. Heating the milk to 73°C for 16 seconds was found to eliminate the contaminating microorganisms.

ACKNOWLEDGMENTS

This research was supported by the USAID Middle East Regional Cooperation (MERC) program under project number PCE–G–00–00–00026, entitled “Multinational Approaches to Enhance Goat Production in the Middle East,” with participants in USA (E (Kika) de la Garza American Institute for Goat Research, Langston University); Egypt (Desert Research Center); Israel (The Volcani Center); Nutrition and Food Technology Department); Jordan (University of Science and Technology), and the Palestinian Authority (Al-Quds University).