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Mango seed uses: thermal behaviour of mango seed almond fat and its mixtures with cocoa butter
Bioresource Technology 92 (2004) 71–78
Mango seed uses: thermal behaviour of mango seed almond fat and its mixtures with cocoa butter J.A. Solıs-Fuentes a
a,*
, M.C. Dur an-de-Baz ua
b,1
Instituto de Ciencias B asicas, Universidad Veracruzana, Av. Dos Vistas s/n carretera Xalapa-Las Trancas, 91000 Xalapa, Ver., Mexico b Departamentos de Alimentos y Biotecnologıa y de Ingenierıa Quımica, PIQAyQA, Facultad de Quımica, UNAM, Edif. ‘‘E’’ planta baja, 04510 Mexico, DF Received 27 April 2003; accepted 10 July 2003
Abstract This paper deals with the physicochemical characterization, including thermal behaviour, by differential scanning calorimetry of mango seed almond fat (MAF), alone and in mixtures with cocoa butter (CB). Results showed that mango almond seeds contain about 5.28–11.26% (dw) of fat. The refraction index is 1.466, the saponification index 189.0 and the iodine index 41.76. Fatty acids found in MAF are oleic, stearic, and palmitic acids (40.81%, 39.07% and 9.29% (w/w), respectively) as well as smaller amounts of linoleic, with arachidic, behenic, lignoceric, and linolenic acids, among others. Calorimetric analysis showed that MAF crystallizes between 14.6 and )24.27 °C with a DHc of 56.06 J/g and melts between )17.1 and 53.8 °C, with fusion maxima at 18.54 °C and 40.0 °C for the a and b polymorphic forms. Their fusion enthalpies are 70.12 and 115.7 J/g. The MAF solids content profile is very similar to that of CB, both in stabilized and non-stabilized samples. The mixing compatibility was analyzed using isosolids curves of mixtures of different compositions. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Mango almond fat; Cocoa butter; Fat blends; Phase change; Fusion enthalpies; Isosolids diagrams
1. Introduction The identification and application of new materials is important for the development of new technological approaches towards the use of traditional raw materials. Agroindustrial residues may become unconventional sources for these traditional raw materials (Solıs-Fuentes, 1998). Vegetable fats and oils are widely used in the food, pharmaceutical, cosmetic and chemical industries and are normally obtained from oilseeds such as sesame seed, soy bean, cotton seed and oil (Gutcho, 1979; Birker and Padley, 1987; O’Brien, 1998). Among these fat and oil sources, cocoa butter (CB) is highly appreciated because of its physical and chemical characteristics. * Corresponding author. Tel.: +52-2288-12-5745; fax: +52-2288-129963. E-mail addresses: [email protected] (J.A. Solıs-Fuentes), mcduran@ servidor.unam.mx (M.C. Duran-de-Baz ua). 1 Fax: +52-55-5622-5303.
0960-8524/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2003.07.003
Developing countries, the traditional producers of these seeds as well as of other agricultural products, are currently confronting environmental challenges due to the excess of agricultural wastes associated with production and exportation trends. To help reverse these problems, attention has been drawn towards the possible use of some of these agroindustrial wastes as nonconventional sources of useful materials, including the industrial use of fats and oils (Ben-Gera and Kramer, 1969; Maurya and Chawdhary, 1977; El-Zanati and Zaher, 1990). The physical, chemical and nutritional properties of fats and oils are limiting factors for their use in certain industrial sectors. Thus, obtaining nutritionally sound products for the food industry will greatly depend on the physical and/or chemical characteristics of the fat and oil formulations. Among these physical and chemical characteristics, thermal behaviour and phase changes are particularly important. In the food industry, for example, vegetable oil hydrogenation modifies its thermal behaviour and stability, making possible its use as a
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J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
substitute for traditional saturated fats of animal origin as lard, butter, etc. (Bertoli et al., 1995; O’Brien, 1998). However, new trends are starting to use less processed fats and oils because of the findings on the role played by trans fatty acids in some human health aspects (Khosla and Sundram, 1996; Solıs-Fuentes and Dur an-de-Baz ua, 2001). These trends open up new perspectives for the use of natural-origin vegetable fat mixtures as alternative sources of fatty products with adequate physical characteristics, such as melting or fusion point, solid contents, and consistency. These mixtures should also possess adequate nutritional properties (Williams et al., 1997; Kloek et al., 2000; Toro-V azquez et al., 2000). Mango seed almonds fat (MAF) has been the subject of several research studies because some of its characteristics show resemblance to those of CB (Narashima-Char et al., 1977; Lakshminarayana et al., 1983; Dhinigra and Kapoor, 1985; MdAlı et al., 1985; MdAli and Dimick, 1994; Jimenez-Berm udez et al., 1995; SolısFuentes, 1998). However, there are no studies of thermal and phase behaviour of MAF from its different varieties, and particularly the physicochemical properties of MAF from Manila variety are scarce. The Manila mango (Mangifera indica, L.) variety is a widely cultivated and processed agricultural product in Mexico, due to its particularly delicious and delicate flavour, its lack of fibres, and the smallness of its seed. Considering that Manila mango might be an interesting source of fat, the aim of this research was: to determine the general composition of mango, var. Manila, its almond seed characteristics, including its fat (MAF) composition and some specific properties. The MAF thermal and phase behaviour were studied and its interactions in mixtures with cocoa butter (CB) were investigated using differential scanning calorimetry (DSC) and drawing the resulting isosolids diagrams.
2. Methods 2.1. Sampling Mangoes from Mangifera indica, L., Manila variety were obtained from a plantation located in the coastal mango-producing zone of the State of Veracruz in Mexico. Two stages of physiological ripeness or maturity were selected, pre-mature and mature, in order to compare the fat contents and the physical and chemical characteristics of both stages.
parts removed (skin, pulp and seed and, from seeds, the almonds) and weighed. Pulp chemical analyses confirmed the ripeness stage. Moisture content (Horwitzs, 1980), ash content (Horwitzs, 1980), titrable acidity (by neutralization), reducing and total sugars content (Lane and Eynon method, cited by Southgate, 1991), pH value (potentiometer measurement), and tannins content (Folin–Denis method, cited by Horwitzs, 1980) analyses were performed. Almonds were also characterized by measuring their content of moisture, ash, fat, crude fibre, protein (Horwitzs, 1980), tannins (Folhin–Denis method, cited by Horwitzs, 1980), and cyanides (alkaline titration). 2.3. Crude fat extraction and further purification Once free of their external protective layer, seed almonds of mature fruits were dehydrated in an oven at 60 °C until they reached a moisture content of about 10%. Once dried, they were manually crushed and ground and stored in polyethylene bags at 5 °C until use. Fat extraction from dried almond seed meal was performed in a Soxhlet apparatus utilizing hexane as solvent. A 6-h extraction was carried out for total removal of fat. Solvent was removed from the resulting product under vacuum using a rotavapour. Fat was kept away from light and air at 5 °C until processing and analysis took place. 2.4. Fat purification MAF of mature fruits was purified using an adaptation of the Wesson method (Mehlenbacher, 1970): crude fat was dissolved in petroleum ether in a ratio 1:5 (w/v). Potassium hydroxide at 14% was added to dissolved fat (1 ml KOH per gram of dissolved fat) with vigorous stirring for 3 min. Then 50% ethyl alcohol was added in a ratio of 1:2.5 (w/v) while stirring and it was left to stand until phase separation. The ether phase contained the neutral fat. The soap alcohol phase was repeatedly reextracted with ether. Ether extracts were processed in a rotavapour to recover purified fat. Purified fat was kept in a freezer (5 °C) away from light until processing and/or analysis. 2.5. Physicochemical properties MAF refraction index, iodine index, saponification index, etc. were analyzed using officially approved techniques (Horwitzs, 1980; Hendrikse et al., 1994).
2.2. Fruits characterization 2.6. Fatty acids pattern The size and proportions of constitutive parts as well as the chemical composition for each stage of ripeness were determined in randomly sampled fruits. Three exemplars for each maturation stage were taken, their
Fatty acids present in the MAF were analyzed using gas chromatography coupled to mass spectroscopy, adapting the Bannon et al. (1982) and Hendrikse et al.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
(1994) methodology. Fat was converted into the corresponding methyl esters of its fatty acids. These were dissolved in heptane, separated by packed column chromatography and passed to a mass spectrometer for identification through comparison of the spectra with previously injected standards. 2.7. Fatty acids methylic esters preparation The boron trifluoride method (AOAC, 1995) was used for fatty acid methyl ester preparation and approximately 1 ml of the resulting heptane layer was transferred to a glass tube and injected into the chromatograph. Chromatograms and mass spectra for each fatty acid methyl ester were obtained. 2.8. Gas chromatography–mass spectroscopy Fatty acid methyl esters analysis was performed in a Hewlett Packard gas chromatograph model 5890 series II, coupled to a mass spectrometer with an electronic ionization detector. The system had an AT Silar capillary column 30 m long, 0.32 mm internal diameter and 0.25 lm film thickness. Compound identification was carried out using a data base complemented with internal standards of fatty acids methyl esters. Helium was the carrier gas with a flow of 0.4 mL/min and a pressure at 50 °C of 38 kPa. Injector temperature was 250 °C and starting oven temperature was 100 °C. The temperature programme was 2 min at 100 °C increased by 4 °C/min to 180 °C which was maintained for a final time of 5 min. The mass analyzer range was 10:450 m/z.
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The temperature programme for the calorimeter was: (a) Cooling to )60 °C and heating at 10 °C/min to 90 °C. Registration of the fusion profile. (b) Heating at 90 °C for 10 min, and cooling at 10 °C/ min to )60 °C. Registration of the crystallization profile. (c) Heating at 90 °C, cooling at )60 °C for 10 min, and heating at 10 °C/min to 90 °C. Registration of the profile and enthalpy of fusion. The enthalpies of fusion needed to melt the fat sample crystals, as well as the crystallization enthalpies needed to solidify them, were calculated using the area below the integration curve and the thermogram baselines. Temperature ranges of fusion and crystallization were determined using the thermograms, through the identification in the curves of the onset and offset temperatures for the phase changes. 2.11. Contents of solid fat The amounts of solids in the fats as a function of the temperature were calculated using DSC experiments, the Lambelet and Raemy (1983), methodology and the computational package Origin (Microcal, 1999). Since solid fat contents (SFC) depend on temperature these values may be presented as a function of temperature. Partial areas of the thermograms were calculated and correlated with solids percentages considering that at )60 °C, samples are 100% solids. 2.12. Thermal behaviour of mixtures MAF–CB
2.9. Cocoa butter Commercially available pure CB was characterized in the same way as MAF (iodine index and fatty acids analysis). 2.10. Thermal profile Samples of purified MAF, and purified CB, were fed to a differential scan calorimeter (Dupont Inst. DSC 910) equipped with a thermal analysis data station (Thermal Analysis 2100). The purging gas used was nitrogen at a flow of 20 mL/min. The instrument was calibrated with indium (melting point, 156.6 °C; DHf , 28.45 J/g). Samples between 5 and 15 mg were weighed in a thermobalance (TA), in aluminium SFI capsules with a precision of ±0.1 mg, which were then hermetically sealed. An empty sealed capsule was used as reference. In order to find the thermal history of the samples, many MAF and CB samples were previously tempered by heating at 90 °C for 5 min and then cooled at 24 °C for 24 h. These samples were then stored for 15 days at 5 °C.
A matrix was created with mixtures of MAF and CB in different proportions. Each sample was prepared with its duplicate and fusion profiles were studied using DSC, following the methodology and equipment described above. Samples were tested before and after stabilization (samples that were stored for 15 days at 5 °C). Solid fat contents were calculated as described above and the diagrams of isosolids were produced using the same Origin (Microcal, 1999) programme and the Statistica programme (StatSoft, 2000).
3. Results and discussion The physiological development of the mangoes used for MAF extraction was characterized using chemical analysis of the pulps. The average compositions (mean ± standard deviation of triplicate analyses) for unripe mango fruits pulps were: moisture content, 74.57 ± 0.26%; pH values of 3.40 ± 0.23; ash content, 1.11 ± 0.22; total sugar content, 24.50 ± 1.05%; titrable acidity, 7.55 ± 0.25; tannins, 0.089 ± 0.008%; and
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
nitrogen-free extract, NFE, 66.73 ± 1.04%, all dry basis, except moisture contents. Mature fruits had: moisture content, 85.07 ± 0.06%; pH values of 4.51 ± 0.09; ash contents, 2.59 ± 0.08%; total sugars, 90.25 ± 0.62%; titrable acidity, 4.1 ± 0.29; tannins, 0.018 ± 0.001%; and FNE, 3.02 ± 0.25%. These values and differences clearly show the inherent characteristics of unripe and mature fruits, with ripeness processes increasing sugar contents and reducing acidity and tannins. Physiological development had no significant effect on the weight of each portion of the fruit (peel, pulp, seed and almond). Values found for both unripe and mature fruits were: average weight 298 g, with peel, 16.11%; pulp, 66.51%; seed, 11.69%, and almond, 5.58%. The almond chemical composition is presented in Table 1, for both unripe and mature fruits. Mature fruits showed the logical changes in proteins, fats, crude fibres, ashes and tannins, resulting from the cellular differentiation and specificity of tissues related with maturity processes. The fat extracted and purified had a solid consistency at environmental temperature of 20–23 °C and presented a cream colour with a characteristic aroma. The physicochemical characteristics of purified samples MAF of mature fruits were: refractive index 1.466, acidity value 0.60% (as oleic acid), saponification index 189.0 and iodine index of 47.7 (average of two determinations). Table 2 presents the analytical results for the GC-ME for MAF and CB (the commercial CB sample had an iodine index of 43.8). In both types of fats, mango almond and cocoa, the fatty acids profiles show oleic, stearic and palmitic acids. For CB, these three fatty acids constitute more than 95% of the total content, giving this fat a relatively simple acylglyceride composition. Depending on the origin of the cacao bean, these acylglycerides vary from 80% to 95% (mainly POP and POS, with some as SOS, where P ¼ palmitic acid, O ¼ oleic acid, and S ¼ stearic acid). These compositions give unique physicochemical characteristics to this fat, determining its thermal and phase conduct (Timms,
Table 1 Chemical composition of Mexican mango var. Manila almonds Characteristics (%)
Unripe fruits a
Moisture contents Ashes contents Fat contents Crude fibre Proteins Tannins Cyanides FNEb a
Mature fruits
Average ±r
Average r
32.98 ± 1.63 1.45 ± 0.012 5.28 ± 1.13 1.24 ± 0.06 1.80 ± 0.02 0.04 ± 0.004 0.01 ± 0.0007 90.14 ± 0.86
19.80 ± 1.17 2.08 ± 0.036 9.36 ± 1.87 7.58 ± 0.32 4.62 ± 0.13 1.60 ± 0.034 0.006 ± 0.001 69.25 ± 6.18
Mean ± standard deviation of triplicate analyses. b Free nitrogen extract.
Table 2 Profile of fatty acidsa in the MAF and in a commercial sample of CB Fatty acid
MAF
CB
Palmitic Stearic Oleic Linoleic Linolenic Arachidic Behenic Lignoceric No identified
9.29 39.07 40.81 6.06 0.64 2.48 0.64 0.49 0.52
24.27 35.10 36.47 2.85 0.30 1.01 – – –
a
Average of duplicate analyses.
1980; Talbot, 1995). According to Table 2, CB has a little over 60% of saturated fatty acids whereas MAF has 52% and the ratio among saturated fatty acids to unsaturated ones is, for CB, 1.52 and for MAF, 1.09. These figures are within the reported values for MAF from other mango varieties, and for CB (MdAlı et al., 1985; Schlichter-Aronhime and Garti, 1988; SolısFuentes, 1998). Fig. 1 shows the thermograms of fusion for stabilized MAF and the solidification thermograms of the same fat after being heated until complete fusion and maintained at 90 °C for 10 min. As may be observed, profiles for phase change S–L and viceversa are relatively simple and closely correspond to the similarly relatively simple fatty acid composition. It is shown that, during fusion, there is a low melting point fraction with fusion starting at a temperature of )17.16 °C and a maximum of 5.32 °C, and a higher melting point fraction, with a less opened peak starting at 26.18 °C and presenting a maximum at 40.01 °C, completing the phase change at around 53.8 °C. The enthalpy change for this fusion process was 115.72 J/g. The cooling process for the melting fat starts the solidification step at 14.64 °C and
2
Cooling
3
4
Heat Flow > >Exo
74
1
1
3
5
2
Heating
4 -80 -60 -40 -20
0
20
40
60
80 100
Temperature, °C Fig. 1. Differential scanning calorimetry crystallization and fusion curves for stabilized MAF. Refer to Table 3 for (1, 2, 3, 4 and 5) transition temperatures.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
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2
Cooling
3
MAF
1
1
2
Heating
1
Heat Flow <
Heat Flow >>Exo
4
5
3
6
23 1
CB
5
4 2 5
3
4 -60 -40 -20
0
20
40
4
60
80
-80 -60 -40 -20
100
0
20
40
60
80 100
Temperature, ºC
Temperature, °C Fig. 2. Differential scanning calorimetry crystallization and fusion curves for stabilized CB. Refer to Table 3 for (1, 2, 3, 4 and 5) transition temperatures.
Fig. 3. Differential scanning calorimetry fusion curves for MAF and CB without stabilization. Refer Table 3 for (1, 2, 3, 4, 5, and 6) transition temperatures.
ends at )24.27 °C, with a crystallization maximum at 10.41 °C. A slight ‘‘shoulder’’ is observed at )9.90 °C, that might be assumed to be the solidification of the low fusion point fraction, constituted by triacylglycerides with unsaturated fatty acids. The value for DHc for this solidification process was 56.06 J/g. Fig. 2 shows the profile of fusion for the CB, stabilized under the same conditions as MAF, and the CB crystallization profile after being completely melted and maintained at 90 °C for 10 min. In this case, the observed fusion and crystallization profiles are also relatively simple and show a great resemblance with those for MAF. The CB also presented the two maxima for fusion. The first one corresponds to the low fusion point fraction, with a maximum temperature of 11.64 °C and the second one corresponds to the higher fusion temperature triacylglycerides with a maximum point at 36.51 °C. The DHf for the CB analyzed was 128.17 J/g. With respect to crystallization, it starts at 12.71 °C with a maximum at 6.38 °C, and a DHc of 56.98 J/g. Similarities in the thermal behaviour of MAF and CB are also evident in Fig. 3 that shows the fusion profiles
for both fats without stabilization and subjected to immediate heating after solidification with rapid cooling. Table 3 presents the more representative transition temperatures in the thermograms, allowing comparison of the CB with the MAF data. According to Hagemann (1988), vegetable origin lipids (fatty acids, acylglycerides, and fats and oils) present polymorphism, and in general, and with more frequency, solidify in three different crystalline forms: a, b0 , and b, with correspondingly higher fusion temperatures. Polymorph a (lowest fusion point) is generally present after rapid cooling processes from melted fat. Form b0 , with a higher melting or fusion point than the previous one, is generated through solidification of fat under certain conditions of temperature or due to transition from form a. Polymorph b, the most stable crystalline form, is produced from the other two forms by incubating at slightly higher fusion temperatures than for the a form. Polymorphism for CB has been widely studied (Lutton, 1957; Schlichter-Aronhime and Garti, 1988; Loisel et al., 1998) and there is still controversy with respect to the number and types of forms in which it crystallizes. One of the most accepted
Table 3 Transition point temperatures and crystallization and fusion enthalpies for MAF and CB Sample
DH (J/g)
Transition temperature (°C) 1
Crystallization MAF CB Fusion Stabilized MAF Non-stabilized MAF Stabilized CB Non-stabilized CB n.d.: Not determined.
2
3
4
56.06 56.98
14.64 12.71
10.41 6.38
)9.90 )15.22
)24.27 )26.17
115.72 70.12 128.17 80.02
)17.16 )15.94 )11.02 )3.50
5.32 )2.31 11.64 8.08
26.18 2.01 22.80 19.70
40.01 10.62 36.51 23.11
5
6
53.84 18.54 52.47 40.18
n.d. 42.23 n.d. n.d.
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Non-stabilized CB
100
Stabilized CB
60
Stabilized MAF
40 20
Non-stabilized MAF
Temperature °C
Solid Fat Content
26
80
0
18
10
50 60 70
6
80
14
2 0.0
-10
0
10
20
30
40
50
60
0.2
Temperature, °C Fig. 4. Solid fat content for stabilized and non-stabilized MAF and CB.
proposals is that it may be crystallized in six different polymorphs (Talbot, 1995). According to this, the fusion thermograms for CB in Figs. 2 and 3 correspond to forms a and b2 respectively, considering the typification of Larsson or to forms II and V as a function of the Wille and Lutton studies (Talbot, 1995). The thermal behaviour for MAF shown in Figs. 1 and 3 suggests that, following the CB case, it is also a bstable fat and different from the so-called b0 -stable fats such as those obtained from palm, soy or colza oil hydrogenation or those known as lauric fats from coconut or palm seeds. Fig. 4 shows the MAF and CB samples solids profiles, stabilized and without stabilization. Similarities can be observed in the behaviour of the solid and liquid phases of the fats due to the temperature effect, when subjected to stabilization. Once stable, MAF is softer than CB at lower temperatures and has a harder consistency at higher temperatures, preserving more solids than CB. This behaviour is probably due to the composition differences, since MAF has a somewhat higher oleic acid content that may have a ‘‘dilution effect’’ for the saturated fatty acids acylglycerides, slightly reducing the fusion point. MAF, on the other hand, contains saturated fatty acids of longer chain, such as behenic and lignoceric acids, that might be influencing the requirements for higher temperatures for MAF complete fusion. As it is well known, fats affect the functional properties of foods, cosmetics and pharmaceutical products. This can be positive or negative depending upon the final product, and may be a multiphase one. The fat phase of a product may be constituted by a fat of single origin or by several fats from different sources and of different compositions, and its stability greatly influences that of the product. The effect of deliberate mixing or the migration of the fat in the product on the thermal behaviour and consistency of the fat phases (resulting from the formation of eutectic products, modification of
0.4
0.6
0.8
1.0
MAF (Weight Fraction)
70
Fig. 5. Isoline diagram of solid fat content (SFC) for mixtures of MAF and CB in non-stabilized samples.
the polymorphic phases, phase separation, etc.) becomes a relevant issue for the overall product quality. Figs. 5 and 6 show the isosolids diagrams for mixtures of MAF and CB. This type of diagram links points of equal contents of solids in the fat, within a composition-temperature graph, as a way of analyzing the interaction of the components and the fusion profiles for the mixtures. If the lines are parallel and approximately horizontal, then the components exhibit good compatibility. If this is not the case, with the extreme case occurring when eutectic mixtures are formed (minimum points), softening effects occur, considering the pure components, or the formation of higher fusion points compounds (Birker and Padley, 1987; Talbot, 1995). In samples without stabilization, the isosolid diagram of Fig. 5 shows that MAF is slightly softer than CB and has a more evident softening effect in mixtures when its contribution to solids is 60–80% by weight. If its contribution to the mixtures is small, the effect is negligible and if higher, when solids content is small, the effect is compensated, and MAF requires higher temperatures than CB to melt. In fact, the profile of fusion for MAF is wider, melting starting at lower temperatures and phase changing completely at higher temperatures than CB.
50 SFC = 5 10 20 30 50 60 70
44 Temperature °C
-20
SFC = 5 10 20 30
22
38 32 26
80
20 0.0
0.2
0.4
0.6
0.8
1.0
MAF (Weight Fraction)
Fig. 6. Isoline diagram of solid fat content (SFC) for mixtures of MAF and CB in stabilized samples.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
The diagram shows a lower compatibility between MAF and CB than between CB and other fats such as Coberine, with isolines more parallel and horizontal during its mixing with CB (Talbot, 1995). It is, however, much more compatible than milk fat, lauric fats and hydrogenated cottonseed oil (Birker and Padley, 1987; Talbot, 1995). Improved compatibility for the stabilized forms type b, shown in Fig. 6 is found with no softening effect at compositions of lower than 20% of MAF, and a harder mixture for compositions higher than 80% of MAF. Again, a wide fusion profile for MAF is shown, requiring lower temperatures than CB to have 80% solids and higher temperatures to melt the last 5% solids of the pure state fat. The diagram of the stabilized mixtures shows the much better compatibility of MAF with CB when compared with lauric fats and with those coming from the hydrogenation of vegetable oils. Based on the results found in this study, mango almond fat from mature fruits of the Manila variety (MAF), widely produced in Mexico, has physicochemical characteristics and a fatty acids profile close to those of CB. The MAF curves for solid–liquid phase change are relatively simple and shows a great resemblance with those of CB. However, the MAF fusion curve is wider than that for CB. The SFC MAF profiles show, just as CB’s, a very steep slope around 30–40 °C. MAF thermal behaviour with and without stabilization suggests the presence of a and b crystalline forms, making it a bstable fat, just as CB. The isosolid diagrams for mixtures of MAF and CB showed that there is compatibility between both fats, even better than that of mixtures of CB with milk fat, lauric fats, or hydrogenated cottonseed oil. Therefore, MAF may be used as a partial substitute for CB in some of its multiple applications. Its properties and thermal conduct also make it suitable for use in mixtures with vegetable oils for specialty fatty products with specific consistencies and characteristics. Finally, MAF and its use would give added value to those residues present in large quantities in the mango nectars and canned and dried products industries in tropical countries.
References AOAC, 1995. In: Cunniff, P. (Ed.), Official Methods of Analysis. AOAC International, Arlington, Virginia. Bannon, C.D., Craske, J.D., Hai, N.T., Harper, N.L., O’Rourke, K.L., 1982. Analysis of fatty acid methyl esters with accuracy and reliability. J. Chrom. 247, 63–69. Ben-Gera, I., Kramer, A., 1969. The utilization of food industries wastes. Adv. Food Res. 17, 77–152. Bertoli, C., Hosszu-Sackett, K., Melachouris, N., Truifler, H., 1995. Preparation of butterfat and vegetable butter substitutes. USA Patent 5395629. Birker, P.J.M.W.L., Padley, F.B., 1987. Physical properties of fats and oils. In: Hamilton, R.J., Bhati, A. (Eds.), Recent Advances in
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Chemistry Technology of Fats and Oils. Elsevier, New York (Chapter 1). Dhinigra, S., Kapoor, A., 1985. Nutritive value of mango seed kernel. J. Sci. Food Agric. 36, 752–756. El-Zanati, E.M., Zaher, F.A., 1990. Utilization of rice bran oil to produce an antifoamer. JAOCS 67 (1), 61–63. Gutcho, M., 1979. Edible oils and fats. Recent Developments. Noyes Data Co., New Jersey. Hagemann, J.W., 1988. Thermal behavior and polymorphism of acylglycerides. In: Garti, N., Sato, K. (Eds.), Crystallization and Polymorphism of Fats and Fatty Acids, vol. 31. Marcel Dekker, New York (Chapter 2). Hendrikse, P.W., Harwood, J.L., Kates, M., 1994. Analytical methods. In: Gunstone, F.D., Hornwood, J.L. (Eds.), The Lipids Handbook, second ed. Chapman and Hall Chemical Database, New York. Horwitzs, W., 1980. Official Methods of Analysis of the Association of Official Analytical Chemists. AOAC, Washington, DC. Jimenez-Berm udez, M., Silva-Hernandez, E.R., Solıs-Fuentes, J.A., Duran-de-Baz ua, M.C., 1995. La grasa de semilla de mango como posible sustituto de la manteca de cacao. In: I Congreso Iberoamericano de Ingenierıa de los Alimentos, November 4–7, 1995. Campinas, S.P. Brazil. Khosla, P., Sundram, K., 1996. Effects of dietary fatty acid composition on plasma cholesterol. Prog. Lipid Res. 35 (2), 93–132. Kloek, W., Walstra, P., Van Vliet, T., 2000. Crystallization kinetics of fully hydrogenated palm oil in sunflower oil mixtures. JAOCS 77 (4), 389–398. Lakshminarayana, G., Chandrasekhara-Rao, T., Ramalingaswamy, P.A., 1983. Varietal variations in content characteristics and composition of mango seed and fat. JAOCS 60 (1), 88–89. Lambelet, P., Raemy, A., 1983. Isosolid diagrams of fat from thermal analysis data. JAOCS 60 (4), 845–847. Loisel, C., Keller, G., Lecq, G., Bourgaux, C., Ollivon, M., 1998. Phase transitions and polymorphism of cocoa butter. JAOCS 75 (4), 425–439. Lutton, E.S., 1957. On the configuration of cocoa butter. JAOCS 34, 521. Maurya, K.R., Chawdhary, D.N., 1977. Utilization of mango wastes. Ind. Food Packer 31, 83–84. Mehlenbacher, V.C., 1970. Analisis de grasas y aceites. Ediciones Urmo, Bilbao. MdAlı, A., Gafur, M.A., Rahman, M.S., Ahmed, G.M., 1985. Variations in fat content and lipid class composition in ten different mango varieties. JAOCS 62 (3), 520–523. MdAli, A.R., Dimick, P.S., 1994. Thermal analysis of palm midfraction, cocoa butter and milk fat blends by differential scanning calorimetry. JAOCS 71 (3), 299–302. Microcal, 1999. Origin 6.0. Microcal Software Inc., Northampton, MA. Narashima-Char, B.L., Reddy, B.R., Thirumala-Rao, S.D., 1977. Processing mango stones for fat. JAOCS 54, 494–495. O’Brien, R.D., 1998. Fat and Oils. Technomic Pub. Co., Lancaster, Penn. Schlichter-Aronhime, J., Garti, N., 1988. Solidification and polymorphism in cocoa butter and the blooming problems. In: Garti, N., Sato, K. (Eds.), Crystallization and Polymorphism of Fats and Fatty Acids, vol. 31. Marcel Dekker, New York (Chapter 9). Solıs-Fuentes, J.A., 1998. El aprovechamiento de residuos s olidos y lıquidos de la agroindustria alimentaria, cinco ejemplos. M.S. Thesis. Facultad de Quımica, UNAM. Mexico, D.F. Solıs-Fuentes, J.A., Duran-de-Baz ua, M.C., 2001. Los acidos grasos trans en los alimentos y algunos efectos de su consumo en la salud. Revista Ciencia (Mexico) 52 (1–2), 4–14. Southgate, D.A.T., 1991. Determination of Food Carbohydrates. Elsevier Applied Science, London. StatSoft, 2000. Statistica for Windows. StatSoft Inc., Tulsa. Timms, R.E., 1980. The phase behavior of mixtures of cocoa butter and milk fat. Lebensm. Wiss. Technol. 13, 61–65.
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Talbot, G., 1995. Fat eutectics and crystallisation. In: Beckett, S.T. (Ed.), Physico-Chemical Aspects of Food Processing. Blackie Academic and Professional. Chapman and Hall, London (Chapter 7). Toro-V azquez, J.F., Brice~ no-Montelongo, M., Dibildox-Alvarado, E., Char o-Alonso, M., Reyes-Hernandez, J., 2000. Crystallization
kinetics of palm stearin in blends with sesame seed oil. JAOCS 77 (3), 297–310. Williams, S.D., Ransom-Painter, K.L., Hartel, R.W., 1997. Mixtures of palm kernel oil with cocoa butter and milk fat in compound coatings. JAOCS 74 (45), 357–366.
Mango seed uses: thermal behaviour of mango seed almond fat and its mixtures with cocoa butter J.A. Solıs-Fuentes a
a,*
, M.C. Dur an-de-Baz ua
b,1
Instituto de Ciencias B asicas, Universidad Veracruzana, Av. Dos Vistas s/n carretera Xalapa-Las Trancas, 91000 Xalapa, Ver., Mexico b Departamentos de Alimentos y Biotecnologıa y de Ingenierıa Quımica, PIQAyQA, Facultad de Quımica, UNAM, Edif. ‘‘E’’ planta baja, 04510 Mexico, DF Received 27 April 2003; accepted 10 July 2003
Abstract This paper deals with the physicochemical characterization, including thermal behaviour, by differential scanning calorimetry of mango seed almond fat (MAF), alone and in mixtures with cocoa butter (CB). Results showed that mango almond seeds contain about 5.28–11.26% (dw) of fat. The refraction index is 1.466, the saponification index 189.0 and the iodine index 41.76. Fatty acids found in MAF are oleic, stearic, and palmitic acids (40.81%, 39.07% and 9.29% (w/w), respectively) as well as smaller amounts of linoleic, with arachidic, behenic, lignoceric, and linolenic acids, among others. Calorimetric analysis showed that MAF crystallizes between 14.6 and )24.27 °C with a DHc of 56.06 J/g and melts between )17.1 and 53.8 °C, with fusion maxima at 18.54 °C and 40.0 °C for the a and b polymorphic forms. Their fusion enthalpies are 70.12 and 115.7 J/g. The MAF solids content profile is very similar to that of CB, both in stabilized and non-stabilized samples. The mixing compatibility was analyzed using isosolids curves of mixtures of different compositions. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Mango almond fat; Cocoa butter; Fat blends; Phase change; Fusion enthalpies; Isosolids diagrams
1. Introduction The identification and application of new materials is important for the development of new technological approaches towards the use of traditional raw materials. Agroindustrial residues may become unconventional sources for these traditional raw materials (Solıs-Fuentes, 1998). Vegetable fats and oils are widely used in the food, pharmaceutical, cosmetic and chemical industries and are normally obtained from oilseeds such as sesame seed, soy bean, cotton seed and oil (Gutcho, 1979; Birker and Padley, 1987; O’Brien, 1998). Among these fat and oil sources, cocoa butter (CB) is highly appreciated because of its physical and chemical characteristics. * Corresponding author. Tel.: +52-2288-12-5745; fax: +52-2288-129963. E-mail addresses: [email protected] (J.A. Solıs-Fuentes), mcduran@ servidor.unam.mx (M.C. Duran-de-Baz ua). 1 Fax: +52-55-5622-5303.
0960-8524/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2003.07.003
Developing countries, the traditional producers of these seeds as well as of other agricultural products, are currently confronting environmental challenges due to the excess of agricultural wastes associated with production and exportation trends. To help reverse these problems, attention has been drawn towards the possible use of some of these agroindustrial wastes as nonconventional sources of useful materials, including the industrial use of fats and oils (Ben-Gera and Kramer, 1969; Maurya and Chawdhary, 1977; El-Zanati and Zaher, 1990). The physical, chemical and nutritional properties of fats and oils are limiting factors for their use in certain industrial sectors. Thus, obtaining nutritionally sound products for the food industry will greatly depend on the physical and/or chemical characteristics of the fat and oil formulations. Among these physical and chemical characteristics, thermal behaviour and phase changes are particularly important. In the food industry, for example, vegetable oil hydrogenation modifies its thermal behaviour and stability, making possible its use as a
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substitute for traditional saturated fats of animal origin as lard, butter, etc. (Bertoli et al., 1995; O’Brien, 1998). However, new trends are starting to use less processed fats and oils because of the findings on the role played by trans fatty acids in some human health aspects (Khosla and Sundram, 1996; Solıs-Fuentes and Dur an-de-Baz ua, 2001). These trends open up new perspectives for the use of natural-origin vegetable fat mixtures as alternative sources of fatty products with adequate physical characteristics, such as melting or fusion point, solid contents, and consistency. These mixtures should also possess adequate nutritional properties (Williams et al., 1997; Kloek et al., 2000; Toro-V azquez et al., 2000). Mango seed almonds fat (MAF) has been the subject of several research studies because some of its characteristics show resemblance to those of CB (Narashima-Char et al., 1977; Lakshminarayana et al., 1983; Dhinigra and Kapoor, 1985; MdAlı et al., 1985; MdAli and Dimick, 1994; Jimenez-Berm udez et al., 1995; SolısFuentes, 1998). However, there are no studies of thermal and phase behaviour of MAF from its different varieties, and particularly the physicochemical properties of MAF from Manila variety are scarce. The Manila mango (Mangifera indica, L.) variety is a widely cultivated and processed agricultural product in Mexico, due to its particularly delicious and delicate flavour, its lack of fibres, and the smallness of its seed. Considering that Manila mango might be an interesting source of fat, the aim of this research was: to determine the general composition of mango, var. Manila, its almond seed characteristics, including its fat (MAF) composition and some specific properties. The MAF thermal and phase behaviour were studied and its interactions in mixtures with cocoa butter (CB) were investigated using differential scanning calorimetry (DSC) and drawing the resulting isosolids diagrams.
2. Methods 2.1. Sampling Mangoes from Mangifera indica, L., Manila variety were obtained from a plantation located in the coastal mango-producing zone of the State of Veracruz in Mexico. Two stages of physiological ripeness or maturity were selected, pre-mature and mature, in order to compare the fat contents and the physical and chemical characteristics of both stages.
parts removed (skin, pulp and seed and, from seeds, the almonds) and weighed. Pulp chemical analyses confirmed the ripeness stage. Moisture content (Horwitzs, 1980), ash content (Horwitzs, 1980), titrable acidity (by neutralization), reducing and total sugars content (Lane and Eynon method, cited by Southgate, 1991), pH value (potentiometer measurement), and tannins content (Folin–Denis method, cited by Horwitzs, 1980) analyses were performed. Almonds were also characterized by measuring their content of moisture, ash, fat, crude fibre, protein (Horwitzs, 1980), tannins (Folhin–Denis method, cited by Horwitzs, 1980), and cyanides (alkaline titration). 2.3. Crude fat extraction and further purification Once free of their external protective layer, seed almonds of mature fruits were dehydrated in an oven at 60 °C until they reached a moisture content of about 10%. Once dried, they were manually crushed and ground and stored in polyethylene bags at 5 °C until use. Fat extraction from dried almond seed meal was performed in a Soxhlet apparatus utilizing hexane as solvent. A 6-h extraction was carried out for total removal of fat. Solvent was removed from the resulting product under vacuum using a rotavapour. Fat was kept away from light and air at 5 °C until processing and analysis took place. 2.4. Fat purification MAF of mature fruits was purified using an adaptation of the Wesson method (Mehlenbacher, 1970): crude fat was dissolved in petroleum ether in a ratio 1:5 (w/v). Potassium hydroxide at 14% was added to dissolved fat (1 ml KOH per gram of dissolved fat) with vigorous stirring for 3 min. Then 50% ethyl alcohol was added in a ratio of 1:2.5 (w/v) while stirring and it was left to stand until phase separation. The ether phase contained the neutral fat. The soap alcohol phase was repeatedly reextracted with ether. Ether extracts were processed in a rotavapour to recover purified fat. Purified fat was kept in a freezer (5 °C) away from light until processing and/or analysis. 2.5. Physicochemical properties MAF refraction index, iodine index, saponification index, etc. were analyzed using officially approved techniques (Horwitzs, 1980; Hendrikse et al., 1994).
2.2. Fruits characterization 2.6. Fatty acids pattern The size and proportions of constitutive parts as well as the chemical composition for each stage of ripeness were determined in randomly sampled fruits. Three exemplars for each maturation stage were taken, their
Fatty acids present in the MAF were analyzed using gas chromatography coupled to mass spectroscopy, adapting the Bannon et al. (1982) and Hendrikse et al.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
(1994) methodology. Fat was converted into the corresponding methyl esters of its fatty acids. These were dissolved in heptane, separated by packed column chromatography and passed to a mass spectrometer for identification through comparison of the spectra with previously injected standards. 2.7. Fatty acids methylic esters preparation The boron trifluoride method (AOAC, 1995) was used for fatty acid methyl ester preparation and approximately 1 ml of the resulting heptane layer was transferred to a glass tube and injected into the chromatograph. Chromatograms and mass spectra for each fatty acid methyl ester were obtained. 2.8. Gas chromatography–mass spectroscopy Fatty acid methyl esters analysis was performed in a Hewlett Packard gas chromatograph model 5890 series II, coupled to a mass spectrometer with an electronic ionization detector. The system had an AT Silar capillary column 30 m long, 0.32 mm internal diameter and 0.25 lm film thickness. Compound identification was carried out using a data base complemented with internal standards of fatty acids methyl esters. Helium was the carrier gas with a flow of 0.4 mL/min and a pressure at 50 °C of 38 kPa. Injector temperature was 250 °C and starting oven temperature was 100 °C. The temperature programme was 2 min at 100 °C increased by 4 °C/min to 180 °C which was maintained for a final time of 5 min. The mass analyzer range was 10:450 m/z.
73
The temperature programme for the calorimeter was: (a) Cooling to )60 °C and heating at 10 °C/min to 90 °C. Registration of the fusion profile. (b) Heating at 90 °C for 10 min, and cooling at 10 °C/ min to )60 °C. Registration of the crystallization profile. (c) Heating at 90 °C, cooling at )60 °C for 10 min, and heating at 10 °C/min to 90 °C. Registration of the profile and enthalpy of fusion. The enthalpies of fusion needed to melt the fat sample crystals, as well as the crystallization enthalpies needed to solidify them, were calculated using the area below the integration curve and the thermogram baselines. Temperature ranges of fusion and crystallization were determined using the thermograms, through the identification in the curves of the onset and offset temperatures for the phase changes. 2.11. Contents of solid fat The amounts of solids in the fats as a function of the temperature were calculated using DSC experiments, the Lambelet and Raemy (1983), methodology and the computational package Origin (Microcal, 1999). Since solid fat contents (SFC) depend on temperature these values may be presented as a function of temperature. Partial areas of the thermograms were calculated and correlated with solids percentages considering that at )60 °C, samples are 100% solids. 2.12. Thermal behaviour of mixtures MAF–CB
2.9. Cocoa butter Commercially available pure CB was characterized in the same way as MAF (iodine index and fatty acids analysis). 2.10. Thermal profile Samples of purified MAF, and purified CB, were fed to a differential scan calorimeter (Dupont Inst. DSC 910) equipped with a thermal analysis data station (Thermal Analysis 2100). The purging gas used was nitrogen at a flow of 20 mL/min. The instrument was calibrated with indium (melting point, 156.6 °C; DHf , 28.45 J/g). Samples between 5 and 15 mg were weighed in a thermobalance (TA), in aluminium SFI capsules with a precision of ±0.1 mg, which were then hermetically sealed. An empty sealed capsule was used as reference. In order to find the thermal history of the samples, many MAF and CB samples were previously tempered by heating at 90 °C for 5 min and then cooled at 24 °C for 24 h. These samples were then stored for 15 days at 5 °C.
A matrix was created with mixtures of MAF and CB in different proportions. Each sample was prepared with its duplicate and fusion profiles were studied using DSC, following the methodology and equipment described above. Samples were tested before and after stabilization (samples that were stored for 15 days at 5 °C). Solid fat contents were calculated as described above and the diagrams of isosolids were produced using the same Origin (Microcal, 1999) programme and the Statistica programme (StatSoft, 2000).
3. Results and discussion The physiological development of the mangoes used for MAF extraction was characterized using chemical analysis of the pulps. The average compositions (mean ± standard deviation of triplicate analyses) for unripe mango fruits pulps were: moisture content, 74.57 ± 0.26%; pH values of 3.40 ± 0.23; ash content, 1.11 ± 0.22; total sugar content, 24.50 ± 1.05%; titrable acidity, 7.55 ± 0.25; tannins, 0.089 ± 0.008%; and
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
nitrogen-free extract, NFE, 66.73 ± 1.04%, all dry basis, except moisture contents. Mature fruits had: moisture content, 85.07 ± 0.06%; pH values of 4.51 ± 0.09; ash contents, 2.59 ± 0.08%; total sugars, 90.25 ± 0.62%; titrable acidity, 4.1 ± 0.29; tannins, 0.018 ± 0.001%; and FNE, 3.02 ± 0.25%. These values and differences clearly show the inherent characteristics of unripe and mature fruits, with ripeness processes increasing sugar contents and reducing acidity and tannins. Physiological development had no significant effect on the weight of each portion of the fruit (peel, pulp, seed and almond). Values found for both unripe and mature fruits were: average weight 298 g, with peel, 16.11%; pulp, 66.51%; seed, 11.69%, and almond, 5.58%. The almond chemical composition is presented in Table 1, for both unripe and mature fruits. Mature fruits showed the logical changes in proteins, fats, crude fibres, ashes and tannins, resulting from the cellular differentiation and specificity of tissues related with maturity processes. The fat extracted and purified had a solid consistency at environmental temperature of 20–23 °C and presented a cream colour with a characteristic aroma. The physicochemical characteristics of purified samples MAF of mature fruits were: refractive index 1.466, acidity value 0.60% (as oleic acid), saponification index 189.0 and iodine index of 47.7 (average of two determinations). Table 2 presents the analytical results for the GC-ME for MAF and CB (the commercial CB sample had an iodine index of 43.8). In both types of fats, mango almond and cocoa, the fatty acids profiles show oleic, stearic and palmitic acids. For CB, these three fatty acids constitute more than 95% of the total content, giving this fat a relatively simple acylglyceride composition. Depending on the origin of the cacao bean, these acylglycerides vary from 80% to 95% (mainly POP and POS, with some as SOS, where P ¼ palmitic acid, O ¼ oleic acid, and S ¼ stearic acid). These compositions give unique physicochemical characteristics to this fat, determining its thermal and phase conduct (Timms,
Table 1 Chemical composition of Mexican mango var. Manila almonds Characteristics (%)
Unripe fruits a
Moisture contents Ashes contents Fat contents Crude fibre Proteins Tannins Cyanides FNEb a
Mature fruits
Average ±r
Average r
32.98 ± 1.63 1.45 ± 0.012 5.28 ± 1.13 1.24 ± 0.06 1.80 ± 0.02 0.04 ± 0.004 0.01 ± 0.0007 90.14 ± 0.86
19.80 ± 1.17 2.08 ± 0.036 9.36 ± 1.87 7.58 ± 0.32 4.62 ± 0.13 1.60 ± 0.034 0.006 ± 0.001 69.25 ± 6.18
Mean ± standard deviation of triplicate analyses. b Free nitrogen extract.
Table 2 Profile of fatty acidsa in the MAF and in a commercial sample of CB Fatty acid
MAF
CB
Palmitic Stearic Oleic Linoleic Linolenic Arachidic Behenic Lignoceric No identified
9.29 39.07 40.81 6.06 0.64 2.48 0.64 0.49 0.52
24.27 35.10 36.47 2.85 0.30 1.01 – – –
a
Average of duplicate analyses.
1980; Talbot, 1995). According to Table 2, CB has a little over 60% of saturated fatty acids whereas MAF has 52% and the ratio among saturated fatty acids to unsaturated ones is, for CB, 1.52 and for MAF, 1.09. These figures are within the reported values for MAF from other mango varieties, and for CB (MdAlı et al., 1985; Schlichter-Aronhime and Garti, 1988; SolısFuentes, 1998). Fig. 1 shows the thermograms of fusion for stabilized MAF and the solidification thermograms of the same fat after being heated until complete fusion and maintained at 90 °C for 10 min. As may be observed, profiles for phase change S–L and viceversa are relatively simple and closely correspond to the similarly relatively simple fatty acid composition. It is shown that, during fusion, there is a low melting point fraction with fusion starting at a temperature of )17.16 °C and a maximum of 5.32 °C, and a higher melting point fraction, with a less opened peak starting at 26.18 °C and presenting a maximum at 40.01 °C, completing the phase change at around 53.8 °C. The enthalpy change for this fusion process was 115.72 J/g. The cooling process for the melting fat starts the solidification step at 14.64 °C and
2
Cooling
3
4
Heat Flow > >Exo
74
1
1
3
5
2
Heating
4 -80 -60 -40 -20
0
20
40
60
80 100
Temperature, °C Fig. 1. Differential scanning calorimetry crystallization and fusion curves for stabilized MAF. Refer to Table 3 for (1, 2, 3, 4 and 5) transition temperatures.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
75
2
Cooling
3
MAF
1
1
2
Heating
1
Heat Flow <
Heat Flow >>Exo
4
5
3
6
23 1
CB
5
4 2 5
3
4 -60 -40 -20
0
20
40
4
60
80
-80 -60 -40 -20
100
0
20
40
60
80 100
Temperature, ºC
Temperature, °C Fig. 2. Differential scanning calorimetry crystallization and fusion curves for stabilized CB. Refer to Table 3 for (1, 2, 3, 4 and 5) transition temperatures.
Fig. 3. Differential scanning calorimetry fusion curves for MAF and CB without stabilization. Refer Table 3 for (1, 2, 3, 4, 5, and 6) transition temperatures.
ends at )24.27 °C, with a crystallization maximum at 10.41 °C. A slight ‘‘shoulder’’ is observed at )9.90 °C, that might be assumed to be the solidification of the low fusion point fraction, constituted by triacylglycerides with unsaturated fatty acids. The value for DHc for this solidification process was 56.06 J/g. Fig. 2 shows the profile of fusion for the CB, stabilized under the same conditions as MAF, and the CB crystallization profile after being completely melted and maintained at 90 °C for 10 min. In this case, the observed fusion and crystallization profiles are also relatively simple and show a great resemblance with those for MAF. The CB also presented the two maxima for fusion. The first one corresponds to the low fusion point fraction, with a maximum temperature of 11.64 °C and the second one corresponds to the higher fusion temperature triacylglycerides with a maximum point at 36.51 °C. The DHf for the CB analyzed was 128.17 J/g. With respect to crystallization, it starts at 12.71 °C with a maximum at 6.38 °C, and a DHc of 56.98 J/g. Similarities in the thermal behaviour of MAF and CB are also evident in Fig. 3 that shows the fusion profiles
for both fats without stabilization and subjected to immediate heating after solidification with rapid cooling. Table 3 presents the more representative transition temperatures in the thermograms, allowing comparison of the CB with the MAF data. According to Hagemann (1988), vegetable origin lipids (fatty acids, acylglycerides, and fats and oils) present polymorphism, and in general, and with more frequency, solidify in three different crystalline forms: a, b0 , and b, with correspondingly higher fusion temperatures. Polymorph a (lowest fusion point) is generally present after rapid cooling processes from melted fat. Form b0 , with a higher melting or fusion point than the previous one, is generated through solidification of fat under certain conditions of temperature or due to transition from form a. Polymorph b, the most stable crystalline form, is produced from the other two forms by incubating at slightly higher fusion temperatures than for the a form. Polymorphism for CB has been widely studied (Lutton, 1957; Schlichter-Aronhime and Garti, 1988; Loisel et al., 1998) and there is still controversy with respect to the number and types of forms in which it crystallizes. One of the most accepted
Table 3 Transition point temperatures and crystallization and fusion enthalpies for MAF and CB Sample
DH (J/g)
Transition temperature (°C) 1
Crystallization MAF CB Fusion Stabilized MAF Non-stabilized MAF Stabilized CB Non-stabilized CB n.d.: Not determined.
2
3
4
56.06 56.98
14.64 12.71
10.41 6.38
)9.90 )15.22
)24.27 )26.17
115.72 70.12 128.17 80.02
)17.16 )15.94 )11.02 )3.50
5.32 )2.31 11.64 8.08
26.18 2.01 22.80 19.70
40.01 10.62 36.51 23.11
5
6
53.84 18.54 52.47 40.18
n.d. 42.23 n.d. n.d.
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J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78 30
Non-stabilized CB
100
Stabilized CB
60
Stabilized MAF
40 20
Non-stabilized MAF
Temperature °C
Solid Fat Content
26
80
0
18
10
50 60 70
6
80
14
2 0.0
-10
0
10
20
30
40
50
60
0.2
Temperature, °C Fig. 4. Solid fat content for stabilized and non-stabilized MAF and CB.
proposals is that it may be crystallized in six different polymorphs (Talbot, 1995). According to this, the fusion thermograms for CB in Figs. 2 and 3 correspond to forms a and b2 respectively, considering the typification of Larsson or to forms II and V as a function of the Wille and Lutton studies (Talbot, 1995). The thermal behaviour for MAF shown in Figs. 1 and 3 suggests that, following the CB case, it is also a bstable fat and different from the so-called b0 -stable fats such as those obtained from palm, soy or colza oil hydrogenation or those known as lauric fats from coconut or palm seeds. Fig. 4 shows the MAF and CB samples solids profiles, stabilized and without stabilization. Similarities can be observed in the behaviour of the solid and liquid phases of the fats due to the temperature effect, when subjected to stabilization. Once stable, MAF is softer than CB at lower temperatures and has a harder consistency at higher temperatures, preserving more solids than CB. This behaviour is probably due to the composition differences, since MAF has a somewhat higher oleic acid content that may have a ‘‘dilution effect’’ for the saturated fatty acids acylglycerides, slightly reducing the fusion point. MAF, on the other hand, contains saturated fatty acids of longer chain, such as behenic and lignoceric acids, that might be influencing the requirements for higher temperatures for MAF complete fusion. As it is well known, fats affect the functional properties of foods, cosmetics and pharmaceutical products. This can be positive or negative depending upon the final product, and may be a multiphase one. The fat phase of a product may be constituted by a fat of single origin or by several fats from different sources and of different compositions, and its stability greatly influences that of the product. The effect of deliberate mixing or the migration of the fat in the product on the thermal behaviour and consistency of the fat phases (resulting from the formation of eutectic products, modification of
0.4
0.6
0.8
1.0
MAF (Weight Fraction)
70
Fig. 5. Isoline diagram of solid fat content (SFC) for mixtures of MAF and CB in non-stabilized samples.
the polymorphic phases, phase separation, etc.) becomes a relevant issue for the overall product quality. Figs. 5 and 6 show the isosolids diagrams for mixtures of MAF and CB. This type of diagram links points of equal contents of solids in the fat, within a composition-temperature graph, as a way of analyzing the interaction of the components and the fusion profiles for the mixtures. If the lines are parallel and approximately horizontal, then the components exhibit good compatibility. If this is not the case, with the extreme case occurring when eutectic mixtures are formed (minimum points), softening effects occur, considering the pure components, or the formation of higher fusion points compounds (Birker and Padley, 1987; Talbot, 1995). In samples without stabilization, the isosolid diagram of Fig. 5 shows that MAF is slightly softer than CB and has a more evident softening effect in mixtures when its contribution to solids is 60–80% by weight. If its contribution to the mixtures is small, the effect is negligible and if higher, when solids content is small, the effect is compensated, and MAF requires higher temperatures than CB to melt. In fact, the profile of fusion for MAF is wider, melting starting at lower temperatures and phase changing completely at higher temperatures than CB.
50 SFC = 5 10 20 30 50 60 70
44 Temperature °C
-20
SFC = 5 10 20 30
22
38 32 26
80
20 0.0
0.2
0.4
0.6
0.8
1.0
MAF (Weight Fraction)
Fig. 6. Isoline diagram of solid fat content (SFC) for mixtures of MAF and CB in stabilized samples.
J.A. Solıs-Fuentes, M.C. Duran-de-Bazua / Bioresource Technology 92 (2004) 71–78
The diagram shows a lower compatibility between MAF and CB than between CB and other fats such as Coberine, with isolines more parallel and horizontal during its mixing with CB (Talbot, 1995). It is, however, much more compatible than milk fat, lauric fats and hydrogenated cottonseed oil (Birker and Padley, 1987; Talbot, 1995). Improved compatibility for the stabilized forms type b, shown in Fig. 6 is found with no softening effect at compositions of lower than 20% of MAF, and a harder mixture for compositions higher than 80% of MAF. Again, a wide fusion profile for MAF is shown, requiring lower temperatures than CB to have 80% solids and higher temperatures to melt the last 5% solids of the pure state fat. The diagram of the stabilized mixtures shows the much better compatibility of MAF with CB when compared with lauric fats and with those coming from the hydrogenation of vegetable oils. Based on the results found in this study, mango almond fat from mature fruits of the Manila variety (MAF), widely produced in Mexico, has physicochemical characteristics and a fatty acids profile close to those of CB. The MAF curves for solid–liquid phase change are relatively simple and shows a great resemblance with those of CB. However, the MAF fusion curve is wider than that for CB. The SFC MAF profiles show, just as CB’s, a very steep slope around 30–40 °C. MAF thermal behaviour with and without stabilization suggests the presence of a and b crystalline forms, making it a bstable fat, just as CB. The isosolid diagrams for mixtures of MAF and CB showed that there is compatibility between both fats, even better than that of mixtures of CB with milk fat, lauric fats, or hydrogenated cottonseed oil. Therefore, MAF may be used as a partial substitute for CB in some of its multiple applications. Its properties and thermal conduct also make it suitable for use in mixtures with vegetable oils for specialty fatty products with specific consistencies and characteristics. Finally, MAF and its use would give added value to those residues present in large quantities in the mango nectars and canned and dried products industries in tropical countries.
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