Physicochemical and sensory characteristics of milk from goats supplemented with castor or licuri oil

Article Outline

• Abstract
• Introduction
• Materials and Methods
  • Experimental Design
  • Physicochemical Determinations
  • Sensory Analysis
  • Statistical Analysis
• Results and Discussion
• Conclusions
• Acknowledgments
• References
• Copyright

Abstract 

The purpose of this study was to evaluate the influence of castor and licuri palm oils supplemented to milking goats on the physical, chemical, and sensory characteristics of milk. A double Latin square experimental design (5×5) using 10 confined crossbred Moxotó-Alpine goats was performed according to the following treatments: nonsupplemented (control), 3% castor oil, 5% castor oil, 3% licuri oil, and 5% licuri oil. Oils in each treatment were supplemented in the dry matter. Castor oil supplementation reduced the fat content and increased the lactose and density of milk. Considering the sensory analysis, a lower acceptability was observed for milk from goats supplemented with castor oil. On the other hand, licuri oil supplementation led to higher acceptability scores for flavor and odor of goat milk.

Key words: acceptability, chemical composition, Syagrus coronata, Ricinus communis

Back to Article Outline

Introduction 

The effects of dietary fats on milk composition have been widely studied (Delacroix-Buchet and Lamberet, 2000; Morand-Fehr et al., 2007, Vasta et al., 2008). Although it is known that ruminant diets must not contain high fat percentage because this could inhibit ruminal fermentation by cellulolytic microorganisms (Jenkins, 1993), even low levels of fat in ruminant diets could lead to major changes in composition and physicochemical traits of milk. Such changes depend predominantly on the fat amount and its fatty acid profiling (Chilliard et al., 2003).

Lipid composition plays an important role in the nutritional quality of goat milk. Lipids are involved in the color and flavor of dairy products, in the yield and firmness of cheese, and in the sensory characteristics of yogurt (Vargas et al., 2008). The presence of small fat globules and high amounts of short- and medium-chain fatty acids in goat milk leads to major changes in the content of free fatty acids during lipolysis, which influences the flavor of products (Chilliard et al., 2003, Haenlein, 2004, Bernard et al., 2009). Flavor and odor are known to be important milk quality traits; they are especially important for goat milk because the sensory attributes play an important role in the acceptability of milk and dairy products.

Of the several factors that might be associated with the sensory attributes and quality of goat milk, feeding is considered to be a key factor. Animal feeding systems are shown to be very important in giving particular features to the milk used in the production of certain cheese types (Alonso et al., 1999; Scintu and Piredda, 2007). Therefore, it is plausible to think that the inclusion of some oils in the diet of goats could add value to goat milk. Although fat supplementation could have a major effect on chemical and sensory characteristics of goat milk, little attention has been paid to the development of feeding strategies using vegetable oils to produce desirable quality traits in goat milk.

Licuri (Syagrus coronata) is a palm tree that is well adapted to semiarid areas of Brazil. Licuri oil is predominantly made up of saturated fatty acids and particular sensory attributes. It has been increasingly used for cooking purposes and might become an important economic commodity for local extractive communities and regions with agricultural limitations.

The cultivation of the castor bean (Ricinus communis L.) also presents an economical opportunity for family agriculture in semiarid northeast Brazil because this plant is very resistant to drought, presents good market value, and can be cultivated together with other vegetables, especially beans. Castor oil has a high polyunsaturated fatty acid profile, and byproducts of oil extraction from castor beans have a high content of protein (Azevedo and Lima, 2001) and could be used in animal feeding after detoxification.

Based on the fatty acid profiles of licuri and castor oils and the potential of these plants to improve the agricultural development of semiarid regions in northeast Brazil, this study evaluated the effects of including licuri or castor oils in the diet of goats on physicochemical and sensory attributes of milk.

Back to Article Outline

Materials and Methods 

Experimental Design 

The experiment was performed at the Field Station for Small Ruminant Research of the Federal University of Paraiba (João Pessoa, Brazil). Ten multiparous crossbred Moxotó × Alpine goats, at d 51 of lactation and weighing 40kg on average, were penned individually; drinking water and feed were provided ad libitum. Diets were formulated according to NRC (1981) to meet the nutritional requirements of goats producing 2kg of milk daily with 4% fat. Feed was supplied as a TMR twice daily in excess (20%) to ensure ad libitum intake. Buffel hay and sliced cactus pear leaves were mixed into the experimental diets. The treatments consisted of the following 5 groups: nonsupplemented (control), 3% castor oil, 5% castor oil, 3% licuri oil, and 5% licuri oil. Oils in each treatment were supplemented in the DM. Experimental diet compositions are shown in Table 1.

Table 1. Percentage composition of ingredients in the diets¹ and chemical composition of rations according to licuri oil or castor oil supplementation levels

1Diets: nonsupplemented (control), 3% castor oil, 5% castor oil, 3% licuri oil, and 5% licuri oil. Oils in each treatment were supplemented in the DM.

2Byproduct of corn flakes.

3Composition per kilogram: 180g of Ca; 90g of P; 10g of Mg; 900mg of F; 3,600mg of Zn; 1,000mg of Cu; 1,500mg of Mg; 80mg of Co; 12mg of Se; 150mg of I; 93g of Na; 145g of Cl; 15g of S; 15,000IU/kg of vitamin A; 27,000IU/kg of vitamin D3; 421mg of vitamin E.

The trial lasted 75 d and comprised 5 experimental periods of 15 d each. The first 12 d of each period was used for adaptation to the diets and the following 3 d were used for data collection.

The goats were manually milked twice daily. Before milking, the udder was cleaned and the strip-cup test was performed to detect mastitis. Postdipping was performed after milking using a commercial iodine solution. Milk yield (kilograms/day) was determined during the last 3 d of each experimental period. A composed sample per animal was collected using proportional amounts from morning and afternoon milkings and used for physicochemical and sensory analyses. Previously sterilized stainless steel bottles (500mL) were used for milk storage.

Physicochemical Determinations 

Physicochemical analyses were carried out on 50 composed milk samples from 5 treatments and 5 periods in a double Latin square design (5 × 5 × 2). Protein content was determined according to AOAC (1998) methods 991.20 and 991.23. Milk DM was obtained according to AOAC (1998) method 925.23. Fat content of milk samples was determined by the Gerber method according to IAL (2005) protocol 433/IV. Lactose was determined by the Fehling reduction method according to IAL (2005) protocol 432/IV, and ashes were determined by milk incineration at 550 to 570°C. Density was measured by a thermolactodensimeter at 15°C and acidity was determined by endpoint titration and expressed as lactic acid.

Sensory Analysis 

Composed milk samples from the 5 periods in each treatment were pasteurized at 65°C for 30min, transferred to sterile amber glass containers, and kept under refrigeration until analyses. Sensory analyses were performed according to Stone and Sidel (1993) in individual booths isolated from noise and odors. Samples (50mL) were served at 7°C in glasses coded with 3-digit random numbers. Between samples, crackers and plain water were served to cleanse the palate. Quantitative descriptive analysis (QDA) was performed in triplicate using 12 trained panelists (50% women, 50% men; 22–38 yr of age). Intensity of goatish odor, goatish flavor, rancid flavor, and sweet flavor was assessed based on a nonstructured 9-cm intensity scale ranging from 1 (extremely weak) to 9 (extremely strong). A glossary of these descriptors is presented in Table 2. Because each sample was related to a given treatment, the panelists tasted 5 samples 3 times (repetitions) each.

Table 2. Glossary of quality descriptors of goat milk developed in consensus by the sensory panel

For the acceptance test, the attributes flavor and odor were evaluated by 48 nontrained panelists (42% women, 58% men; 20–40 yr of age) according to a hedonic scale ranging from 1 (dislike very much) to 9 (like very much). Panelists were frequent goat milk consumers that were recruited from students, employees, and professors at the Federal University of Paraiba, Brazil.

Statistical Analysis 

A simultaneous double Latin square (5 × 5) experimental design was used, with 10 animals randomly distributed into 5 treatments and 5 periods. The statistical model used in the analysis of the physicochemical data was the following:

where Y_ijkl is the observation of goat j in period k submitted to treatment i, with i, j, and k=1, 2, 3, 4, 5; μ is the general effect of the mean; Q_i is the effect of the Latin square, with Q=1,2; T_i is the effect of treatment i, with i=1, 2, 3, 4, 5; P_k is the effect of period k; A is the effect of goat l in square i, with l=1, 2, 3, 4, 5; QT is the interaction of the effect of Latin square i with treatment j; and ξ_ijk is the random error associated with each observation Y_ijkl.

The statistical model of sensory analysis data contained only the fixed effect of the treatment. Treatment means were compared by Tukey test at 5% error probability using statistical software (SAS, 1999).

Back to Article Outline

Results and Discussion 

According to the proposed model, no square effect was observed, but significant differences (P<0.01) between treatments were observed for fat, lactose, dry extract, and density. No differences (P>0.05) were observed in the composition of milk from goats supplemented with licuri oil compared with control animals (Table 3). On the other hand, the addition of 3% castor oil decreased (P<0.05) milk fat content by about 17% (Table 3). This finding could be explained by the high amount of ricinoleic acid, a monounsaturated acid, found in castor oil; the increase of unsaturated fatty acid concentrations led to partial biohydrogenation of fat (Lana et al., 2005; Silva et al., 2007). The decrease in the content of milk fat in cows is most likely caused by 2 conditions in the rumen: 1) abnormal fermentation with pH decrease and 2) an acetate:propionate ratio less than 3 caused by concentrate excess as well as the presence of unsaturated fat in the diet (NRC, 2001). Moreover, Cenkvàri et al. (2005) reported that the supplementation of linseed oil with Ca-soap (Ca-Agcl) decreased fat in goat milk. It must also be considered that in case of intense biohydrogenation, the proportion of saturated fatty acids will be greater, which can reduce their availability in the intestines. This could explain the decrease in fat when using castor oil. In this sense, the high percentage of saturated fatty acids in licuri oil, mostly lauric acid (C12:0), might explain the consistency in the fat contents of milk from goats supplemented with licuri oil, which is in accordance with previous findings (Jenkins et al., 2008; Bernard et al., 2009).

Table 3. Physicochemical composition of milk of crossbred Moxotó-Alpine goats without oil supplementation (control group) and supplemented with licuri oil or castor oil at levels of 3 and 5% in the DM

a–cMeans followed by different superscript letters in the same line differ by Tukey test at 5%.

Conversely, Chilliard et al. (2003) reported an increase in the fat contents of milk from goats fed different types of unsaturated oil. Moreover, a significant increase in the percentage of fat in milk from crossbred Moxotó goats fed 5% sunflower oil was observed (Fernandes et al., 2008).

It is noteworthy that the fat decrease in milk from goats supplemented with 5% castor oil was not statistically different (P>0.05) from the control group. In view of the knowledge already available, the results shown herein support the hypothesis that the percentage of fat in milk might vary according to the fat sources and concentrations. Indeed, it has been shown that fat contents in goat milk differ considerably in studies using different fat sources, soluble carbohydrates, and fiber levels (Chilliard et al., 2003).

Castor oil supplementation increased milk lactose contents (P<0.05) compared with the control and licuri oil-supplemented groups, which is in accordance with previous studies evaluating fat supplementation in goats receiving isocaloric diets (Sklan, 1992; Fernandes et al., 2008). Furthermore, a strong correlation between lipid supplementation and lactose production was observed in goats fed protected fat (Sanz Sampelayo et al., 2002). The increase in lactose contents in milk could be associated with the spare of some fatty acids normally used in the fat synthesis or acetyl CoA derived from fatty acids used in the lactose synthesis in mammary glands (Bauman et al, 2006). On the other hand, no effect of licuri oil supplementation on milk lactose contents was observed (P>0.05). Indeed, Chilliard et al. (2003) observed no significant differences in lactose contents between milk samples from nonsupplemented and supplemented goats using different types of vegetable oils.

Castor oil supplementation increased milk density significantly (P<0.05) as shown in Table 3. This could be explained by the increase in lactose and the decrease in fat in milk from goats supplemented with castor oil because fat has lower density than other milk constituents. No differences (P>0.05) were observed between treatments regarding protein, ashes, and acidity.

Results of QDA are shown in Table 4. There was no effect (P>0.05) of licuri oil supplementation on the sensory attributes of goat milk. Supplementation with 3 and 5% of castor oil led to a slightly stronger (P<0.05) goatish odor. Rancid flavor was more intense (P<0.05) when castor oil was included in the animal diet; scores were 5.3 and 5.5 for 3 and 5% of castor oil inclusion rates, respectively. It is known that higher amounts of fat in milk can lead to high rates of lipolysis and proteolysis and therefore promote more intense rancid flavor (Chilliard et al., 2003). However, it is important to consider that the more evident rancid flavor was seen in milk samples with decreased fat contents (3% castor oil). Furthermore, physicochemical and sensory properties and sensory acceptability were not affected by the percentage of vegetable oil (3 and 5%) when milk samples from the same type of oil were considered. Therefore, the present findings suggest that the rancid flavor could be linked to the lipid composition of the oil because unsaturated fatty acids are much more reactive than saturated fatty acids (Attaie and Richter, 1996; Soryal et al., 2005). In fact, castor oil shows high contents of polyunsaturated fatty acids. It must be considered that hydrolytic reactions of triglycerides produce fatty acids of low molecular weight (butyric, caproic, and caprylic acids), which lead to unpleasant odor and flavor (Zan et al., 2006).

Table 4. Average sensory scores¹ of quantitative descriptive analysis for milk of crossbred Moxotó-Alpine goats without oil supplementation (control group) and supplemented with licuri oil or castor oil at levels of 3 and 5% in the DM

a,bMeans followed by different superscript letters in the column differ by Tukey test at 5%.

1Scored based on a nonstructured 9-cm intensity scale ranging from 1 (extremely weak) to 9 (extremely strong).

To identify the sensory attributes that most contributed to distinguishing the differences between the samples of milk from the goats fed diets containing licuri or castor oils, a principal component (PC) analysis was performed using the mean values given by the panelists and the repetitions using a correlation matrix (Figure 1).

• 
  • View Large Image
  • Download to PowerPoint

• Figure 1. 

  Principal component analysis of the milk of Moxotó crossbred goats fed diets containing licuri or castor oils. F1 and F2 refer to principal components 1 and 2, respectively.

The first 2 components together were able to explain 98.66% of the variability between the samples. According to the PC chart, PC1 discriminated castor oil samples that were stronger in all descriptors, and PC2 discriminated 3 and 5% samples from each other and control from licuri samples by sweet flavor. It is interesting because there was no significant difference in the sweet flavor of milk from oil-supplemented goats in QDA analysis (Table 4). The correlation matrix results (data not shown) indicate a positive correlation between sweet flavor and goatish flavor. The high correlation between rancid flavor and goatish odor (Figure 1) could indicate the fact that goatish odor of goat milk could be linked to the hydrolysis of fatty acids, which is known to cause rancid flavor.

Considering the acceptance test (Table 5), no differences (P>0.05) between milk from goats supplemented with licuri oil and control animals were observed regarding odor and flavor traits. The smaller odor score (P<0.05) seen in milk samples from goats supplemented with 5% licuri oil when compared with castor oil supplementation is probably a result of the higher intensity of goatish odor observed for those samples (Table 4).

Table 5. Average acceptance scores¹ for milk of crossbred Moxotó-Alpine goats without oil supplementation (control group) and supplemented with licuri oil or castor oil at levels of 3 and 5% in the DM

a–cMeans followed by different superscript letters in the column differ by Tukey test at 5%.

1Scored according to a hedonic scale ranging from 1 (dislike very much) to 9 (like very much).

There was a significant reduction (P<0.01) in the palatability (flavor) of milk from goats supplemented with castor oil when compared with milk from the control group, which could be attributed to fat rancidity. In fact, the flavor of goat milk is highly correlated to the lipid contents and lipolysis in milk. According to Jaubert et al. (1997), the intensity of flavor varied significantly because of lactation period, fat, and free fatty acid contents and somatic cell counts. On the other hand, factors such as breed, herd size, pH, acidity, and protein concentration have not been shown to play an important role in the sensory attributes. Despite these statements, it can be noted that even though the milk from animals supplemented with licuri oil presented a higher fat percentage compared with the animals receiving castor oil, no differences regarding the sensory characteristics (flavor and odor) were detected by the assessors. This is possibly because of the richness of saturated fatty acids in licuri oil.

Back to Article Outline

Conclusions 

The inclusion of castor oil as a supplement in goat feed modifies the physicochemical characteristics of the milk, especially fat content, aside from accentuating the rancid flavor in the sensory profile. On the other hand, licuri oil did not influence any of the parameters studied. Further studies on the characterization of fatty acid profiles and volatile compounds in milk from goats supplemented with vegetable oils could contribute to understanding the physical, chemical, and sensory changes in milk and, consequently, to developing animal feeding strategies aimed at improving goat milk quality attributes.

Back to Article Outline

Acknowledgments 

The authors thank BNB (FUNDECI/Banco do Nordeste) and CAPES (Coordenação de Aperfeiçoamento de Nível Superior) for financial support. We are also thankful to Tricia Gearhart and Erin Hisrich from The Ohio State University for the English review. We also thank Deborah dos Santos Garruti from CNPAT/Embrapa and Raimundo N. B. Lobo from CNPC/Embrapa for assistance with the statistical analysis.

Back to Article Outline

References 

1. Alonso L, Fontecha J, Lozada L, Fraga MJ, Juarez M. Fatty acid composition of caprine milk: Major, branched-chain, and trans fatty acids. J. Dairy Sci. 1999;82:878–884
   • View In Article
   • Abstract
   • Full-Text PDF (134 KB)
   • CrossRef
2. AOAC. Official Methods of Analysis. 16th ed. 4th rev.. Arlington, VA: Association of Official Analytical Chemists; 1998;
   • View In Article
3. Attaie R, Richter RL. Formation of volatile free fatty acids during ripening of Cheddar-like hard goat cheese. J. Dairy Sci. 1996;79:717–724
   • View In Article
   • Abstract
   • Full-Text PDF (861 KB)
   • CrossRef
4. Azevedo DMP, Lima EF. Aspectos econômicos do agronegócio da mamona. In:  Azevedo DMP,  Lima EF editor. O Agronegócio da Mamona no Brasil. Campina Grande, PB, Brazil: Embrapa Algodão; 2001;p. 21–42
   • View In Article
5. Bauman DE, Mather IH, Wall RJ, Lock AL. Major advances associated with the biosynthesis of milk. J. Dairy Sci. 2006;89:1235–1243
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (236 KB)
   • CrossRef
6. Bernard L, Shingfield KJ, Rouel J, Ferlay A, Chilliard Y. Effect of plant oils in the diet on performance and milk fatty acid composition in goats fed diets based on grass hay or maize silage. Br. J. Nutr. 2009;101:213–224
   • View In Article
7. Cenkvàri É, Fekete S, Feble H. Investigation on the effects of Ca-soaps of oil linseed on rumen fermentation in sheep on milk composition of goats. J. Anim. Physiol. Anim. Nutr. (Berl.). 2005;89:172–178
   • View In Article
   • MEDLINE
   • CrossRef
8. Chilliard Y, Ferlay A, Rouel J, Lamberet G. A review of nutritional and physiological factors affecting goat milk lipid synthesis and lipolysis. J. Dairy Sci. 2003;86:1751–1770
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (357 KB)
   • CrossRef
9. Delacroix-Buchet A, Lamberet G. Sensorial properties and typicity of goat dairy products. In: Proceedings of the 7th International Conference on Goats, Tours, France. Little Rock, AR: International Goats Association; 2000;p. 559–563
   • View In Article
10. Fernandes MF, Queiroga RCRE, Medeiros AM, Costa RC, Bomfim MAD, Braga AA. Physico-chemical characteristics and fatty acid profile of milk of crossbred Moxotó goats supplemented with cottonseed or sunflower oil. Braz. J. Anim. Sci. 2008;37:703–710
    • View In Article
11. Haenlein GFW. Goat milk in human nutrition. Small Rumin. Res. 2004;51:155–163
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (96 KB)
    • CrossRef
12. IAL. Normas Analíticas do Instituto Adolfo Lutz [Analytical Guidelines of Instituto Adolfo Lutz]. São Paulo, Brazil: Instituto Adolfo Lutz; 2005;
    • View In Article
13. Jaubert, G., J. O. Bodini, and A. Jaubert. 1997. Flavor of goat farm bulk milk. Pages 89–93 in Recent Advances in Goat Research. Cahiers Options Méditerranéennes. V. 25. 6th International Conference on Goats, Beijing, China. P. Morand-Fehr, ed. CIHEAM-IAMZ, Saragossa, Spain.
    • View In Article
14. Jenkins TC. Lipid metabolism in the rumen. J. Dairy Sci. 1993;7:3851–3863
    • View In Article
15. Jenkins TC, Wallace RJ, Moate PJ, Mosley EE. Recent advances in biohydrogenation of unsaturated fatty acids within the rumen microbial ecosystem. J. Anim. Sci. 2008;86:397–412
    • View In Article
16. Lana RP, Camardelli MML, Queiroz AC, Rodrigues MT, Eifert EC, Miranda EN, et al. Use of soybean oil and propolis in the diets of milking goats. R. Bras. Zootec. 2005;34:650–658
    • View In Article
17. Morand-Fehr P, Fedele V, Decandia M, Le Frileux Y. Influence of farming and feeding systems on composition and quality of goat and sheep milk. Small Rumin. Res. 2007;68:20–34
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (288 KB)
    • CrossRef
18. NRC. Nutrient Requirement of Dairy Goats. Washington, DC: National Academy of Sciences; 1981;
    • View In Article
19. NRC. Nutrient Requirements of Dairy Cattle. 7th ed.. Washington, DC: National Academy of Sciences; 2001;
    • View In Article
20. Sanz Sampelayo MR, Pérez L, Martín Alonso JJ, Amigo L, Boza J. Effects of concentrates with different contents of protected fat rich in PUFAs on the performance of lactating Granadina goats. Part II. Milk production and composition. Small Rumin. Res. 2002;43:141–148
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (91 KB)
    • CrossRef
21. SAS Institute. SAS User's Guide: Statistics. Cary, NC: SAS Institute; 1999;Version 8.0
    • View In Article
22. Scintu MF, Piredda G. Typicity and biodiversity of goat and sheep milking products. Small Rumin. Res. 2007;68:221–231
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (204 KB)
    • CrossRef
23. Silva MMC, Rodrigues MT, Branco RH, Florentino CA, Sarmento JLR, Queiroz AC, et al. Suplementação de lipídios em dietas para cabras em lactação: Consumo e eficiência de utilização de nutrientes [Effects of fat supplements on intake and efficiency of nutrient utilization in lactating dairy goats]. R. Bras. Zootec. 2007;36:257–267
    • View In Article
24. Sklan D. A note on production responses of lactating ewes to calcium soaps of fatty acids. Anim. Prod. 1992;55:288–291
    • View In Article
25. Soryal K, Beyene FA, Zeng B, Bah BK. Effect of goat breed and milk composition on yield, sensory quality, fatty acid concentration of soft cheese during lactation. Small Rumin. Res. 2005;58:275–281
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (114 KB)
    • CrossRef
26. Stone H, Sidel JL. Sensory Evaluation Practices. 2nd ed.. London, UK: Academic Press; 1993;
    • View In Article
27. Vargas M, Cháfer M, Albors A, Chiralt A, González-Martínez C. Physicochemical and sensory characteristics of yogurt produced from mixtures of cows’ and goats’ milk. Int. Dairy J. 2008;18:1146–1152
    • View In Article
28. Vasta V, Nudda A, Cannas A, Lanza M, Priolo A. Alternative feed resources and their effects on the quality of meat and milk from small ruminants. Anim. Feed Sci. Technol. 2008;150:175–186
    • View In Article
29. Zan M, Stibilj V, Rogelj I. Milk fatty acid composition of goats grazing on alpine pasture. Small Rumin. Res. 2006;64:45–52
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (150 KB)
    • CrossRef