Chapter 7
Agro - Industrial Utilization (continued)

TABLE 2
Composition of Experimental Diets to Test the Vitaminic Effect of P. juliflora Pod Syrup

Legend: Diets with:
M     : milk.
IV     : incomplete vitamin complex distributed for free.
CV   : complete vitamin mix prepared in accordance with the recommendations of WHTR-3/UNUP-129 (1980).
S      : P. juliflora pod syrup.
F      : P. juliflora pod flour.
Np   : Non-protein diet.

Results and Discussion

Pod Processing

The main problem in P. juliflora pod flour processing resulted from its high content of soluble sugars, which makes grinding and sifting difficult. Meyer et al. (1980) overcame this difficulty by modifying the disc mill, a solution not applicable in this case, as it could not be used by the Brazilian Northeast's rural communities. Souza et al. (1983) showed a method for extracting Prosopis juliflora seeds for germination purposes, which consisted of 4 to 8 minutes boiling and the addition of strong acids, a process not suitable for food preparation. The P. juliflora pod processing method described here has the advantage of being easy to apply in rural conditions, in addition to making use of the entire pod (Figure 1).

Chemical Analyses

The 12.4% protein concentration found in the whole pod (Table 3) is in line with the values found by Azevedo (1957) and by Del Valle (1983). Lipid content, at 1.3%, is similar to that reported by Barbosa (1977) and Campos (1980), of 0.83% and 1.1%, respectively, and different from that found by Del Valle (1983), of 3.2%. The 5.2% lipid content and 21.8% protein content in flour were considerably higher that those found in whole pods (Table 3). This relative increase is due to the removal of soluble sugars for making syrup and the removal of fibers through sifting. In this regard, P. juliflora pod flour could be considered better than similar foodstuffs commonly found in the region (Table-incap, 1961).

The 19.2% fiber content, although high, is no reason for concern, as it can be brought down to the recommended levels by adding other fiber-poor components, such as corn and wheat. Although a certain drop in protein content occurs, mixture values are not affected. Zolfaghari (1984) improved protein value of a diet by supplementing wheat flour with 30% P. glandulosa flour, giving a per of 1.5, significantly higher than that for a 100% wheat flour diet.

The removal of soluble sugars from the pods (Fig. 1) made the flour less hygroscopic, reducing moisture to 9.7%; this contributed to making pods last longer, as they are easily deteriorated by insects and micro-organisms. Table 3 summarizes the amounts of calcium, iron, phosphorus and manganese, which are similar to those reported for other legumes (Table-incap, 1961). Starch test was negative, confirming the findings of Becker and Grosjean (1980).

Anti-nutrients

Hegnauer (1958) reported cyanate in P. juliflora pods in the form of glycosides, but no quantification was performed. Park (1977) did not detect cyanate in P. tamarugo; Cruse (1973), and Becker and Grosjean (1980) could not demonstrate cyanate release in P. velutina or P. glandulosa. In this research study, no cyanate release was detected with the picric acid method either in P. juliflora pods or flour samples. Trypsin inhibitor activity, at a rate of 0.22 iu/mg of sample, and of 0.40 iu/mg of protein, was found in Prosopis juliflora raw pod extract; after heating, this activity disappeared completely. No hemoaglutinant activity was detected either in pods or in flour.

Aminogram

Table 4 shows the amino acid composition of flour compared with the amino acid composition of whole pods (Del Valle et al., 1983) and with the requirements of the rats and standard score. The aminogram of P. juliflora pod flour differs from the aminograms reported by Figueiredo (1975) and by Becker (1981), as these authors only determined them for seeds. The flour analyzed here has other components in addition to seeds, and some amino acids are removed by extracting syrup and by sifting. A 44% loss was observed in sulfurated amino acids; 36% for valine and 26% for lysine, when compared with those reported by Del Valle et al., (1983). Flour aminogram showed lysine, threonine and methionine plus cystein as first, second and third limiting amino acids, respectively (Table 4). Nevertheless, flour amino acids are better, compared with those of fao/who (1973) standard score, than compared with those of rat requirements; this was taken into consideration when the findings of the biological tests for protein quality were analyzed (Table 5). Worthy of mention is the fact that P. juliflora pod flour meets the essential amino acid requirements of adult people (fao/who, 1973).

Nutritional Evaluation

Table 5 shows the effects of P. juliflora pod flour on rat growth and the per and npr values (1.2 and 2.6, respectively), being these lower than those of the standard protein, but superior to those of cereals found commonly in the region, such as corn flour (per 0.7) and wheat flour (per 0.68) (Satterlee, 1977). The 1.2 per value found for P. juliflora pod flour was lower than that reported by Del Valle (1983), of 1.4 for whole pods. This difference can be accounted for by the loss of essential amino acids during processing. P. juliflora pod flour nutritional value is higher than that of other species of Prosopis, as shown by Becker (1980), who found negative per for P. pubescens.

Animal weight gain (Figure 2), with 52.8% of that shown by animals fed on casein, was below normal, but showed linear behavior, suggesting thereby that it may have been due to lack of amino acids. No toxic factor interfered with animal performance once the anti-nutritional factors were neutralized by the manufacturing process.

Table 5 shows that although diet intake with P. juliflora pod flour was similar to that for the standard diet, Net Protein Utilization did not correspond to the value expected, being a mere 32, even though digestibility was 79%. This npu value is lower than that reported by Del Valle et al. (1983), of 39.8 for whole pods. This suggests the hypothesis that amino acid loss can be the factor responsible for the decrease in flour nutritive value. Several authors have discussed the nature of this association (Allison, 1949; Bressani, 1977; Coelho et al., 1978; whtr/unup-1980), and suggest that the drop may be due to other factors. The high fiber content in the flour probably hinders complete enzymatic protein digestion, as suggested by Del Valle et al. (1983). Bressani (1977) observed that the relative excess of an essential amino acid can diminish protein utilization. In this study, the relative excess of arginine found in P. juliflora pod flour can activate the urea cycle and decrease dissemination of other amino acids, as well as compete with intestinal absorption of lysine. The absence of starch in Prosopis juliflora observed in this study agrees with the data reported by Becker and Grosjean (1980) for P. velutina and P. glandulosa; the polysaccharide found by Figueiredo (1975) and by Meyer et al. (1980) does not seem to really supply the calculated amount of calories.

Protein and Lipid Analysis

The serum protein values differ significantly (P<0.005) from the normal values for the rat breed (Table 6), but this can be attributable to the low protein content of the experimental diets. No difference was observed between the serum protein values for both groups (casein and Prosopis juliflora), suggesting more influence of the amount of protein in the diet that of its quality. The liver protein levels of animals fed on experimental diets were similar to those normal for the Westar breed. Prosopis juliflora protein quality appears to have no significant effect on rat serum protein.

Serum triglyceride values for both groups were below those normal for the Wistar breed, and the lowest values found for animals fed on P. juliflora pod flour agreed with the large liver lipid deposit of these animals (Table 6). These data are in line with the findings of Kihlberg et al., (1964) for diets with 10% protein, where liver fat content was 16.0% for casein diets, 26.7% for wheat flour and 30.6% for rye bread. The liver fat deposit caused by a diet with 10% protein shows that part of the problem was more a result of protein level in the diet than of protein quality.

Analysis of the Effects of P. juliflora Pod Syrup

The addition of P. juliflora pod syrup to good-quality protein, such as casein, does not affect negatively per, npr and digestibility values (Table 7), considering protein content (5.0%) and lack of toxicity. The presence of large amounts of digestible carbohydrates makes it possible to use it as calory source in food preparations where sweeteners are required.

It is a known fact that good-quality protein utilization is negatively affected when the diet is prepared with an insufficient vitamin complex, as shown in Table 8. The diets' nutritional parameters (Table 8) show that diet 9, made up of P. juliflora pod flour, presented a nutritive value similar or better than that of diet 6, which contains incomplete vitamin complex; similarly, the nutritive value of diet 5, made up of milk and P. juliflora pod syrup, was similar to that of diet 2, with milk and complete vitamin complex, and a little better than that of diet 1, with milk and incomplete vitamin complex, as evidenced by the per and npr values of these diets. The findings for P. juliflora pod flour digestibility containing syrup and/or vitamin are compatible with those reported in literature for wheat flour (77%) and corn meal (72%) (Satterlee et al., 1977).

The data presented suggest the existence of a vitamin complex in P. juliflora pod syrup adequate for meeting the animals' metabolic needs.

TABLE 3
Proximate Composition of P. juliflora Pods and Flour with Dry Weight Base

^a: In mg/100 g Ca 12; P 333; Fe 6.6; Mn 120.
^b: INCAMP table (1961)

TABLE 4
Essential Amino Acid Composition of P. juliflora Pod Flour

a: Expressed in g/16g N
b: Data from Del Valle et al. (1983)
c: FAO/WHO (1973)
d: NRC (1972)
e: Not essential for adults.

Figure 2. Weight gain of rats fed on diets containing P. juliflora pod flour and casein. Each point represents the mean ± standard deviation for six rats.

TABLE 5
P. juliflora Protein Quality

a: All diets contained 10% protein.
b: Results expressed as mean value ± standard deviation.
c: Results obtained at pools of animals, due to the demands of the method.

TABLE 6
Blood Serum and Liver Proteins and Triglycerides^(a) in Rats Fed on P. juliflora Pod Flour

(a) Triglycerides were determined in pools of serum and liver from 6 rats.
(b) Results obtained (mean ± standard deviation) from 6 rats from this laboratory's colony.
(c) Data from Waynforth (1980).
(d) Data from Flores et al. (1969).
(e) Results of mean ± standard deviation.

TABLE 7
Effects of P. juliflora Pod Syrup on Milk Protein Quality

a: Diets were adjusted to contain 10% protein at the expense of corn starch.
b: Results obtained from pools of 6 rats.

TABLE 8
Assessment of the Vitaminic Effect of P. juliflora Pod Syrup on Milk Protein and P. juliflora Pod Flour Protein Quality

a All diets were adjusted to contain 10.0% protein at the expense of corn starch, according to WHTR - 3/UNUP - 129 (1980), being thereby modified as regards carbohydrates and vitamins. Non-protein diets were used for each type of diet with the purpose of determining NPR.

Conclusions

The trials revealed important factors brought about by P. juliflora pod flour processing, such as an increase in protein content in comparison with whole pods, elimination of antinutritive substances, such as cyanogenetic glycosides, hemoaglutinant activity, trypsin and chemotrypsin inhibitors. The nutritive parameters analyzed as per, npr, npu and digestibility showed values similar to those of other common legumes or higher than those of other plant proteins. Some factors interfere with the nutritive value of the by-products studied, such as amino acid imbalance and high ash level, frequently found in foodstuffs of plant origin. The value of serum protein for animals fed on Prosopis juliflora was similar to those of the control group, while liver triglycerides were higher. Such variations were probably due more to protein quantity than to quality. The addition of P. juliflora pod syrup to foodstuffs of animal and plant origin, respectively, keeps the protein utilization efficiency rates constant. The substitution of a vitamin complex by P. juliflora pod syrup kept the same performance of the animals tested, suggesting thereby vitamin content in the syrup.

Acknowledgments

This research project received financial support from cnpq (National Scientific and Technological Development Council), Proc. No. 01700015/82. The authors express their gratitude to Dr. A.J. Pausztai, of Rowet Research Institute (Aberdeen, Scotland), for the npu tests and for the amino acid analyses of P. juliflora pod flour.

References

allison, j. b., 1949: “Biological evaluation of proteins,” Advan. Protein Chem., 5: 155.

aoac, 1970: “Official methods of analysis,” horwitz, w., (Ed.), Association of Official Analytical Chemists, Washington, dc.

azevedo, g., 1957: “Relatório de viagem ao Peru, Chile, Argentina e Uruguai,” Ed. Min., Agricultura.

barbosa, h. p., 1977: “Valor nutritivo da algaroba (Prosopis juliflora (Sw) dc), através de ensaio de digestibilidade em carneiros,” M. Sc. thesis, Universidade Federal de Viçosa, Viçosa, Minas Gerais.

barros, n.a.t., 1981: “Substitução do melaço da cana de açucar pelo da algarobeira na alimentação de carneiros,” M. Sc. thesis, Universidade da Paraíba, Areia, pb.

becker, r., 1981: “The nutrition value of Prosopis pods,” u.s. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, Berkeley, ca.

becker, r. and grosjean, o.k., 1980: “A compositional study of pods of two varieties of Mesquite (Prosopis glandulosa and Prosopis velutina),” J. Agric. Food Chem. 28: 22.

bressani, r., 1977: “Nutrification in foods,” In: Nutritional Evaluation of Food Processing, harris, r.s. and karmas, e. 2nd Ed., avi Publishing Co., Westport, Connecticut.

campos, J., 1980: “Tabelas para cálculo de racões,” M. Sc. thesis, Imprensa Universitária, Universidade Federal de Viçosa, Viçosa, mg.

clark, e.p. and collip, J.b., 1923: “Study of the Tisdall method of determination of blood serum calcium with a suggested modification,” J. Biol. Chem., 63: 461.

coelho, l. c. b. b.; medeiros, r. b. and flores, h., 1978: “Stability to storage of amino acid composition and biological quality of irradiated macaçar beans, Vigna unguiculata, L. Walp.,” J. Food. Sci. 43: 215.

comite interdepartamental de nutricion para la Defensa Nacional, Institutos Nacionales de la Salud, 1961: “Tabla de composición de alimentos para uso en América Latina,” Instituto de Nutrición de Centro América y Panamá, Apartado Postal 1188, Ciudad de Guatemala, Guatemala, Centro América.

cruse, r. r., 1973: “Desert plant chemurgy,” Econ. Bot. 27: 210.

del valle, f.r.; escobedo, m.; muñoz, m. J.; ortega, r. and bourges, h., 1983: “Chemical and nutritional studies on mesquite beans (Prosopis juliflora),” J. Food Sci. 48: 914.

fao/who, 1973: “Energy and protein requirements,” Ad hoc Expert Committee World Health Organization Tech. Report, Series No. 522, Rome, Italy.

figueiredo, a.a., 1975: “Lebensmittelchemisch relevanter Inhaltsstoff der Schoten der Algarobeira (Prosopis juliflora dc),” Ph. D. thesis, Würzburg, Germany.

fiske, c.h. and subbarow, v., 1925: “The colorimetric determination of phosphorus,” J. Biol. Chem. 66: 375.

flores, h.; sierralta, w. and monckeberg, f., 1969: “Triglyceride transport in protein depleted rats,” J. Nutr. 100: 375.

nrc, 1972: “Nutrient requirements of domestic animals,” No. 10, Nutrient requirements of laboratory animals, 2nd Ed., Washington, dc, National Academy of Sciences, National Research Council.

osborne, t. b. and mendel, l. b., 1919: “The nutritive value of wheat kernel and its milling products,” J. Biol. Chem. 37: 557.

pak, n.; araya, h. and cafati, c., 1977: “Calidad proteica y contenido de hemoglutininas en semillas y en estado seco de frijoles (Phaseolus vulgaris) var. coscorrón,” Arch. Latinoamer. Nutr. 27: 91.

richardson, m.; campos, f. d. a. c.; moreira, r.a.; ainouz, i.l.; begbie, r.; watt, w.b. and pusztai, a., 1984: “The complete amino acid sequence of the major (alpha) subunit of the lectin from the seeds of Diolea grandiflora (Mart),” Europ. J. of Bioch. 144: 101.

satterlee, l. d.; kendrick, j.g. and miller, g. a., 1977: “Rapid in vitro assays for estimating protein quality,” Nut. Reports Int. 16: 197.

soloni, f.g., 1971: “Simplified manual micromethod for determination of serum triglycerides,” Clin. Chem. 17: 529.

souza, s.m.; lima, p. c. f. and araujo, m. s., 1983: “Sementes de algaroba: Métodos e custos de beneficiamento,” Revista Brasileira de Sementes, 5: 51.

thivend, p.; mercier, c. and guilbot, a., 1972: “Determination of starch with glucoamylase,” Ch. 14, in: Methods in carbohydrate chemistry, Vol. 4, whistler, r. l. and bemiller, j.n. (Ed.), Academic Press, New York, ny, p.100.

waynforth, h. b., 1980: “Experimental and surgical technique in rat,” Academic Press, London, p. 240.

whtr-3/unup-129, 1980: “Nutritional evaluation of protein foods,” pellet, p.l. and young, v.r., (Ed.), The United Nations University, Shibuya-ku, Tokyo.

zolfaghari, r., 1984: “Nutritional evaluation of honey from mesquite pod and seed (Prosopis glandulosa),” Dissertation Abstracts International B 45: 722.

zucas, s. m. and arruda, a. a. r., 1968: “Determninação do manganes na fração cinzas do alimento,” Rev. da Fac. de Farm. e Bioq. de São Paulo, Vol. 6: 23.

A Contribution to the Study of Alternative Sources of Food: Coffee-Substitute from P. juliflora Pods

Renata Lúcia Vieira
Nonete Barbosa Guerra
Edleide M. Freitas Pires

Nutrition Department
Universidade Federal de Pernambuco

Introduction

Literature published in 1943 (Algaroba: Estudios, utilidades, aplicação, 1960) on the uses of the P. juliflora fruit, a leguminous tree, record its use as food for human consumption. In Argentina, several by products thereof were consumed, the species most commonly used being Prosopis nigra, Prosopis alba and Prosopis panta, by people living in semi-arid areas. Among these products, were the “añapa,” crushed pods with water or milk, and fermented alcoholic beverages, such as “aloja”.

P. juliflora pods were first sun-dried and then stored for consumption during the winter; for this purpose, they were ground and the resulting flour was sifted. Among its many uses, this flour was also used as “wrapping” for mistol cakes, made from Zizyphus mistol Gris.; for ellaborating “patay,” by mixing the flour with water, molding the dough and then baking. It was an important foodstuff for people living in the central and northern provinces, as replacement for traditional bread.

In Santiago del Estero, consumption of “bolanchao” —made from mistol paste and wrapped in P. juliflora pod flour—was common. As early as the 1940's, the Dietetics Regulation Bureau of Buenos Aires set standards for these products according to their composition. Subsequent studies showed them to be food items with high assimilable calcium content, as well as good sources of thiamine and riboflavin.

A substitute for coffee was prepared from Prosopis nigra and related species, similar to the use of Ceratonia siliqua in Europe. In the Brazilian Northeast, the species used in the preparation of a substitute of traditional coffee is P. juliflora.

Other types of legumes, known as “Nescafé,” “morró,” “salsa,” “mangirioba,” “mucunã” and others, abundant in the semi-arid region of the State of Pernambuco, are also being used by the rural population for preparing a substitute for traditional coffee.

In recent studies (Azevedo, 1982) on the importance of P. juliflora for the semi-arid Brazilian Northeast, particular attention is given to its adaptability and ability to thrive under the edaphoclimatic conditions prevailing in that region, and focus on the contribution this species can make to the regional agricultural and livestock economy.

The utilization of P. juliflora in the semi-arid Northeast as an alternative source of food gains increasing importance, envisaging it for replacing a number of traditional food items, such as coffee, bread and others. Its acceptability as coffee substitute derives mainly from its organoleptic characteristics. Additionally, this legume has physico-chemical characteristics that are very compatible with the legal requirements set forth in the standards for extracts obtained from fruits or cereals, such as coffee and malt, respectively.

Material and Methods

The material used as coffee substitute was obtained from pods collected at the semi-arid region of the State of Paraíba; the comparative material was made up by various samples of coffee purchased at the local market (Recife). The P. juliflora pods were first left to dry on the plant itself, then laid under the sun to complete drying. Once dried, they were subjected to torrefaction in clay pots and then ground by hand, so as to replicate the process employed in its region of origin.

The product thus obtained, as well as the samples of commercial coffee, were subjected to physico-chemical analyses.

Moisture content, fixed and acid-soluble mineral residues, caffeine, aqueous, alcoholic and ether extracts, and group B vitamins were measured, according to the standards set forth by the Instituto Adolfo Lutz.

Furfural content in aqueous extract was determined by the qualitative method (Villavechia, 1963); total nitrogen, mineral salts, and total and reducer sugar content were determined by volumetric methods (Schweizerisches Lebensmittel Buch, 1964). Tannin content was also measured, as per Burns.

Results and Discussion

Legislation regarding physico-chemical standards for foodstuffs sets forth, for coffee, the limits presented in Table 1. The substitute made from P. juliflora pods showed values comparable to those required, as shown in Table 2. Mean value of the different variables resulting from these analyses constitute quality indicators. The characteristics of the product showed some variation, derived from the corresponding variation in the process parameters, such as temperature and duration of roasting, and uniformity of exposure to heat. The structural changes occurring in the compounds when the pod is heated, together with the release of compounds prompted by the temperature under which the process was carried out, lead to changes in yield, physico-chemical and organoleptic characteristics such as aroma, color and, consequently, to variations in product acceptability.

The handicraft quality of the process at the regions where the samples were collected is the principal factor behind the lack of final product uniformity; the correction of these factors, however, can be relatively easy to achieve, without eliminating the manual treatment altogether, just by adding certain controls to the processes already used by the local population.

Coffee made from P. juliflora pods has an aroma which, in fact, is similar to that of traditional coffee, resulting not only from caramelization of sugar, but also from hydrolysis and elimination of several compounds, depending both qualitatively and quantitatively on the roasting methods. The aromatizing agents of natural origin have a tradition of use that exempted them for many years from toxicologic tests (Fennaroli's Book of Flavor Ingredients, 1971). Furfural has long been known to be present in the aroma of toasted coffee, being the caramelization of sugar used for reconstituting coffee's natural aroma. The presence of furfural in its substitute made from P. juliflora was verified by qualitative tests, occurring with intensitites similar to those detected for traditional coffee. The presence of high sugar content (specifically 44.13% saccharose) in P. juliflora pods used in the process leads to great similitude between the aroma of the substitute and the aroma of traditional coffee. Theoretical assumptions were compatible with the results of sensorial perception.

TABLE 1
Physico-Chemical Characteristics of Roasted Ground Coffee

TABLE 2
Physico-Chemical Characteristics of Coffee Substitute Made from P. juliflora Pods

According to the comparative reference data (Table 1), the product under study presented a high content of mineral residue; however, this residue was constituted mainly by calcium, thereby lending it a higher nutritive value. Caffeine content, although influenced by variations in the process, showed advantage from the economic point of view, same as the high concentration of aroma observed by sensorial analyses, which lends the product a higher extraction yield. The low fat content does not affect final product quality, when assessed from the dietary point of view. It is rather a point of advantage in the food market.

The tannin content (close to 2.0%) found in the samples contributed to accentuate its characteristic aroma; it does not interfere, as confirmed by sensorial analysis, with the acceptability of the product as a substitute for coffee.

Despite the high nitrogen content found (close to 6.8% in N × 6.25), it was completely absent in the hot aqueous extract, which affords certain atoxic character to the final product.

It was also expected that the product would provide good amounts of complex B vitamins, which could be verified by carrying out the corresponding analyses.

Conclusions

The following conclusions may be derived from the findings of this study:

1. The material under study has good physico-chemical and organoleptic characteristics for the end uses considered;

2. From the toxicologic viewpoint, it presents characteristics that are similar to those of traditional coffee, which it substitutes in certain regions;

3. From the economic viewpoint, the product has probable potential for industrial or semi-industrial application, with satisfactory performance.

References

algaroba: 1960: “Estudios, utilidades, aplicação,” 5th Ed., 90 p.

almeida, j. t. de, 1983: “Algarobeira: promissora forrageira para a região semi-árida,” Salvador, ba., In: Serie de Estudos Diversos, 13, emater-ba.

azevedo, c. de, 1982: “Algarobeira na alimentação animal e humana,” In: Proceedings, I Simpósio Brasileiro sobre Algaroba, Natal, emparn, pp. 238–239.

associacao brasileira das industrias de alimentos, 1978: “Compêndio de Normas e Padrões para Alimentos,” Res., pp. 12–78.

burns, r. f.,: “Methods of the tannin analysis for forage crop evaluation,” University of Georgia, College of Agricultural Sciences, Tec. Bul. 32.

fennaroli's handbook of flavor ingredients, 1971, Cleveland, Ohio, Chem. Rubb.

figueiredo, a., 1984: “Algarroba: promissora alternativa para o Nordeste brasileiro,” (Compilation of findings and data from 1970 to date), In: Proceedings, vii Congresso Brasileiro de Ciencia e Technologia de Alimentos, Fortaleza, pp. 142–143.

instituto adolf lutz, 1976: “Normas analíticas do Instituto Adolf Lutz,” São Paulo, (1).

rachie, k. o. et al., 1979: “Tropical legumes: Resources for the future,” Nat. Acad. of Sci. Wash.

schweizerisches lebensmittelbuch, 1964, Erster Band, Eidgen, Drucksachen und Materialzentrale, Bern.

villavechia, v., 1963: “Tratado de Química Analítica Aplicada,” Vol. ii, Gili Ed., Barcelona.

Evaluation of Flour from Prosopis juliflora and Prosopis pallida Pods in Bakery and Extrusion-Cooking Products

Gastón E. Cruz Alcedo

Industrial Engineer
Universidad de Piura, Peru
Collaborating Scientist at the Natural Resource Investigation Program

Introduction

The district of Piura, in the north of Peru, has 150,000 ha of Prosopis trees, which average a pod output of 2,000 kg/ha/year. Total output is distributed as follows: commercial crop: 60,000 metric tons; in situ consumption: 180,000 metric tons; lost output: 60,000 metric tons. Consumption refers to animal feed (Castro, 1982; Min. Agric. Peru, 1980).

The two main species present are Prosopis juliflora and Prosopis pallida (Ferreyra, 1984).

Dr. Javier Pulgar Vidal, a Peruvian historian and geographer, has stated that pre-inca cultures from this region named this tree Ta-co, which meant “food crop,” and before sugar cane arrived, ancient Peruvians drank “yupisín,” a sweet beverage made by adding water to ground ripe pods. At present, there are manufacturers of “algarrobina” in Piura, a kind of syrup made by concentrating a Prosopis pod infusion (Castro, 1982).

The pods, in addition to being an energy source and having a relatively hih protein value, can be produced at low cost (Azevedo, 1960).

Flour has been manufactured from dry ripe pods, which, despite its almost total lack of starch, can be used in composite flours (Meyer, 1984).

This paper presents the findings of the rheologic tests on composite flours with these pods, and their utilization in bread, biscuits and extruded snacks.

Materials and Methods

Pod drying, milling and separation to obtain flour were performed at the Universidad de Piura chemistry laboratory (whose Faculty of Engineering is carrying out a Natural Resource Research Program and an afforestation program with Prosopis sp.).

With the assistance of the Farinology Laboratory of the Escuela Superior Politécnica del Litoral (espol), Guayaquil, Ecuador, rheologic tests on composite flours were performed, together with bakery and extrusion-cooking experiments.

Figure 1. Pod structure.

Flour elaboration process

Prosopis pod flour is obtained by grinding only the fruit pericarp, because seed and endocarp are very hard and, therefore, difficult to grind. Figure 1 shows a pod diagram (Castro, 1982).

The pods, previously broken in 4- to 5-cm-long pieces, were dried in a gas oven, at a constant 60° C for 8 hours.

A Corona manual disc-mill was then used, setting the gap between discs at 3 to 4 mm, so as to allow endocarp and seed to pass without breaking. The product was then sifted consecutively through 1.2-mm and 250 μm sieves. Grading of particles passing through the second sieve was made using a laboratory rotary sieve.

To compare with results from other authors, some analyses of pod flour chemical composition were performed, in accordance with aoac Standard Methods (aoac, 1980).

Composite flours

Three samples were prepared with Prosopis pod flour sifted through 250 μm mesh and common wheat flour, to determine rheologic characteristics:

1. 100% wheat flour
2. 5% pod flour - 95% wheat flour
3. 10% pod flour - 90% wheat flour

To evaluate consistency and dough development time of these samples, a Barbender Farinograph with a 300-g mixing bowl and 60-rpm mixing speed was used, along with a Chopin Extensigraph to assess resistance and extensibility.

Leavened sweet bread

Bread was elaborated according to the traditional composition and procedure for “sweet bread” using wheat, detailed as follows:

Procedure: 1) Yeast activation, with sugar diluted in water, 10 min.; 2) Kneading: add the other ingredients in the bowl; mix for 3 min. at low speed and 10 min. at high speed; 3) First fermentation: 35 min.; 4) Manual molding.; 5) Second fermentation: 90 min.; 6) Electric oven: 215°C, 12 min.

Composition and procedure were modified when Prosopis pod flour was used, as follows:

wheat flour 500g = 96%
pod flour 20g = 4%
Water 190 ml

The remaining ingredients were not modified.

Procedure: 1) Yeast activation: 10 min.; 2) Kneading: 12 min.; 3) First fermentation: 35 min.; 4) Manual molding; 5) Second fermentation: 90 min.; 6) Baking: 230° C, 8 min.

Biscuits

Conventional composition for biscuits was taken as reference for the experiment:

To bake biscuits with composite wheat-pod flour, the modifications shown in Table 1 were made:

TABLE 1
Modified Ingredients for Biscuits with Composite Flour: Wheat-P. juliflora

Procedure: 1) Mix water, sugar, sugar syrup, powder milk, and pod flour; 2) Let it cool; 3) Add the other ingredients and knead until a homogeneous dough is formed; 4) Molding biscuits: samples A and B in Polin molding machine, in 24-unit trays. Samples C and D manually molded; 5) Electric oven: 205° C, 12 min.

Extrusion-cooking snacks

An espol gelatinization-extrusion Mapimianti Mod. G20 pilot plant was used to make frying-expandible flakes (such as cornflakes), using the following ingredients:

Extrusion-Cooking Snacks

Temperature in gelatinization worm: 8 – 110 – 140 - 125°C
Pressure at extruder head: 180 bar
Drying conditions: 50° C, 9 hours
Frying conditions: in vegetable oil, 200°C, 8 seconds.

Results and Discussion

Figure 2 shows a chart of the drying of 3.8 kg of pods, weighed several times during the process; moisture remaining at the end of drying was also measured.

In general, drying time and temperature must be increased when the pods are very thick. To avoid pod roasting, temperature must not exceed 70° C.

Figure 2. Drying curve for P. juliflora.

Pod moisture after drying must be lower than 7%; otherwise the disc mill will get clogged. It is important to sift immediately after milling, as the highly hygroscopic nature of the product makes it form clots after a few hours, rendering impossible the removal of seeds and endocarp.

Figure 3 shows the fractions obtained after separation. Although flour accounts for only 25% in this case, it is feasible to mill once more the exocarp fraction, raising flour yield up to 35%.

Figure 3. Products separated by sifting.

The following results were obtained from grading of Prosopis pod flour:

Table 2 shows the chemical composition of Prosopis pod flour obtained through the analyses performed. The composition of wheat (Pomeranz, 1978), rye, soybean, potato (Pyler, no date), and green banana (Paz and Quaglia, 1983) flours are also shown for comparison purposes.

TABLE 2
Chemical composition of flours, %

* Source: Meyer (1984).

It may be observed that Prosopis pod flour differs remarkably from other flours, particularly because of its lack of starch. This is one of the limiting factors for using this flour in leavened bread.

Prosopis pod flour vitamin and sugar content is being researched at present at Universidad de Piura.

Rheologic characteristics of pod-wheat composite flours

Figures 4, 5, and 6 show the farinograms for composite flour samples A, B and C, respectively.

These farinograms provide data on two important parameters: water absorption of dough at 500 b.u. consistency (Barbender Units, arbitrary units of consistency), related to optimum water content; and development time, which is related to optimum mixing time.

Development time is measured from the moment water is added to the dough until the point of maximum consistency is reached (9). The results are presented in Table 3.

TABLE 3
Farinographic Parameters

* Based on 300 g = 100% of flour

Lower water absorption is a consequence of lower wheat gluten content in composite flours (fao, 1973).

Figures 7, 8, and 9 are alveograms of wheat-pod composite flour samples A, B, C, respectively.

An alveogram provides information related to dough resistance and extensibility at a prefixed water content. For the test, a dough disc is held on the base plate of the alveograph. Then, air is forced through an orifice on the base plate under the dough disc, forming a bubble which expands until blowing up. The instrument plots pressure vs. time. Maximum height (P) and curve length (L) are used as a measure of extensibility and resistance against deformation. The area under the curve is proportional to deformation work (W). The P/L ratio expresses the balance between resistance and extensibility (Pomeranz, 1978).

Table 4 shows the alveographic values for the composite flours tested.

Figure 4. Farinogram of sample A

Figure 5. Farinogram of sample B.

Figure 6. Farinogram of sample C

Figure 7. Alveogram of sample A

Figure 8. Alveogram of sample B

Figure 9. Alveogram of sample C

TABLE 4
Alveographic Values

Resistance decreases with content of Prosopis pod flour, which, from a practical point of view, means less water absorption. Extensibility increases with Prosopis pod flour content, which seemingly entails easier kneading. However, when the bread manufacturing trial was made, composite pod flour kneading problems arose provoked by other factors.

Results of bread manufacturing trial

Although the alveographic values indicate significant kneading facility, dough containing 5% pod flour was very sticky, adhering to the mixing bowl. It was necessary to add wheat flour to correct this deficiency.

Figure 10 illustrates dough expansion during second fermentation. It can be seen that dough containing pod flour does not expand enough, producing thereby smaller volume bread.

Figure 10. Dough expansion

Baked bread was left to cool off, measuring thereafter the physical parameters shown in Table 5.

TABLE 5
Results from Bread Baking

An organoleptic examination was made by several people, with the following results:

Bread with pod flour, despite the smaller volume, presented an excellent appearance. Crumb was firm (good porosity), but less elastic than that from wheat flour when the bread was pressed with the fingers. The smell is very good. There is reportedly a slightly bitter aftertaste.

Results for biscuits

Samples A and B prepared at espol, were subjected to an acceptance test at the city of Piura. The corresponding questionnaire is shown in Figure 11 below.

Figure 11. Questionnaire concerning biscuit acceptance.

All organoleptic characteristics received good and regular qualifications. Most of the people reported a bitter but not disagreeable aftertaste, more perceptible on sample B. Samples C and D were tasted by many visitors at Universidad de Piura; they reported that both quality and taste were superior to those of commercial biscuits.

Results of extrusion-cooking trial

Table 6 shows that flakes with 10% of Prosopis pod flour expand farther after frying, which means a lighter product, with very good appearance. Color and taste are better than those from other conventional products of corn and wheat.

TABLE 6
Characteristics of Extrusion-Cooking Products

Conclusions

It is feasible to produce a fine powder with dry ripe Prosopis pods, milling these with a disc-mill and removing seeds and endocarp. This technology must be transferred to the rural areas of Piura district, since the necessary equipment is available at the local market and it does not require specialized operation.

Prosopis pod flour, due to its lack of starch, can be used in a 5%-mix with wheat flour to make leavened bread. High percentages of pod flour may cause substantial changes in the rheologic characteristics of the dough, such as less resistance, increased extensibility, adherence to kneading utensils, producing thereby bread with less elasticity and less volume than bread made from wheat flour.

In biscuit manufacturing, Prosopis pod flour replaced wheat flour up to 25%. Its high saccharose content makes it possible to decrease sugar requirements in traditional biscuit recipes. A slightly bitter aftertaste has been reported in the biscuits, which some people seem fo favor.

The best results were obtained with extrusion-cooking products. A pilot extrusion-cooking plant may be envisioned at Universidad de Piura to launch Prosopis pod flour products into the local market.

After the trials, some people who tasted the products reported constipation effects. Therefore, it is convenient to investigate the presence of some components in Prosopis pod flour which might cause this effect.

Some of the first experiments with Prosopis pod flour solubility in milk suggest that this flour could be used to manufacture an instantaneous soluble powder for breakfast beverages.

In the medium term, Universidad de Piura expects results of a work about utilization of Prosopis seeds to increase protein content of composite flours with lower cost than wheat flour and with high starch content.

References

aoac., 1980: “Official Methods of Analysis,” 13th Ed.

azevedo, g., 1960: “Algarroba,” Rio de Janeiro, Brazil.

castro, v., 1982: “Obtención de productos nutritivos y organoplásticos del fruto de algarrobo y su posible industrialización,” Piura, Peru.

fao, 1973: “Composite flour program,” Rome, Italy.

ferreyra, r., 1984: “Estudio sistemático de los algarrobos de la costa norte del Perú,” unmsm, Lima, Peru.

meyer, d., 1984: “Processing, utilization and economics of mesquite pods as a raw material for the food industry,” Zürich, Switzerland.

ministerio de agricultura del peru, 1980: “Estudio para el aprovechamiento integral de la algarroba,” Piura, Peru.

paz, r. and quaglia, g., 1983: “Caracterización química nutricional de la harina de banano verde y de sus productos derivados de amplio consumo,” Guayaquil, Ecuador.

pomeranz, y., 1978: “Wheat chemistry and technology,” Minnesota, usa.

pyler, e. j.: “Baking science and technology,” Chicago, usa.