J Sci Food Agric 1994,65,303-306

Composition and Potential Uses of Mesquite Pods-(Prosopis paZZida L) : Comparison with Carob Pods (Ceratonia siliqua L) Laura Bravo," Nora Gradosb and Fulgencio Saura-Calixto"* a Instituto del Frio (CSIC), Departamento de Nutricibn y Metabolismo, Ciudad Universitaria, 28040 - Madrid, Spain

(Received 24 September 1993; revised version received 14 January 1994; accepted 3 March 1994)

Facultad de Ingenieria. Universidad de Piura, Apartado 353, Piura, Peru

Abstract: The composition of mesquite pods (Prosopis pallida L) (PP), a legume cultivated in the large desert areas of Peru, was studied. These fruits have at the present time very little practical or commercial use. Taking into account the morphological and compositional similarities to Mediterranean carob pods (Ceratonia siliqua L) (CS), which are widely used in the food industry, some applications of PP are considered. PP shows better nutritional properties than CS, mainly owing to its lower polyphenolic content and higher protein digest- ibility.

Key words : mesquite pods, Prosopis pallida, carob pods, composition, uses.

INTRODUCTION

The tree legume Prosopis spp occurs in arid zones of America, Africa and Asia, where 44 species have been reported (Becker et al 1984). Prosopis trees produce indehiscent pods that are palatable to humans and animals.

Prosopis pallida (PP) is a specie which can be found growing in the large desert areas of Peru. The use of the fruits-mesquite pods-is currently almost completely non-existent. Extension of this culture has been recom- mended to prevent desertification. To achieve this objective it is essential to increase the utilisation of the fruits and thereby the economic viability of this culture.

On the other hand, Ceratonia siliqua (CS) is a peren- nial tree of the Leguminosidae family which is widely cultivated in the Mediterranean area. The fruit-arob pod-is a valuable export for some countries, and its uses in the food industry are well established (Ancarani 1976).

Mesquite and carob pods have some compositional and morphological similarities. The objective of our study was to study the composition of PP pods and, by

* To whom correspondence should be addressed.

comparison with CS, to suggest some potential uses for the American pod.

EXPERIMENTAL

Mesquite pods were collected from 25 trees in the desert area of Piura (Peru).

Prior to analysis, the pulp, including exo-, meso- and endocarp (original moisture content 100 g kg-') was dried (vacuum, 5 5 ° C 48 h) and ground (particle size ~ 0 . 5 mm). Seeds, which are made up of pericarp, germ and endosperm, were roasted (160"C, 12 min) and ground in a high-speed mill. Germ was separated (screening by air classifier) and the endosperm-pericarp mixture was filtered to remove the pericarp after extrac- tion of the water-soluble fraction. Ethanol was then added to the filtrate, and the precipitated fraction was washed with acetone, dried and ground (<0.5 mm) giving a gum powder.

The insoluble and soluble dietary fibre contents of the pulp were determined according to Prosky et a1 (1988). The polysaccharide content of the fibre fractions was determined as the sum of neutral sugars (quantified by gas-liquid chromatography (GLC) as alditol acetates according to Englyst and Cummings (1988), and uronic

303 J Sci Food Agric 0022-5142/94/$09.00 0 1994 SCI. Printed in Great Britain

304 L Bruvo, N Grados, F Saura-Calixto

acids (quantified as described by Scott (1979) after acidic hydrolysis. The residue corresponded to Klason lignin.

The neutral sugar composition of the seed gum was determined, after acid hydrolysis of the polysaccharide, by analysing the liberated sugars as alditol acetates by GC (Englyst and Cummings 1988).

Other analytical methods used are listed in Table 2.

RESULTS AND DISCUSSION

Mesquite and carob pods show similar morphological aspects. There are only small differences in length, width, thickness and pulp weight, as can be seen in Table 1. PP yields fewer seeds than CS.

The analytical results for the major constituents of PP pulp are shown in Table 2. Some compositional data of CS taken from the literature (Saura-Calixto and Caiiellas 1982; Saura-Calixto 1987, 1988) are also included for comparative purposes.

As to the seeds, the germ contains about 65 g kg-' protein and the components of the cuticula are lignin and polysaccharides (Saura-Calixto et a1 1991a).

The gum was the main component of the endosperm (940 g kg-' DM). The proportions of galactose and mannose were 410 and 550 g kg-', respectively. These values for this galactomannan are similar to those of guar gum (400 and 600), the gum most commonly used by the food industry, but the mannose level is lower than that of carob pod gum (23 : 77) (Gaisford et a1 1986).

TABLE 1 Morphological parameters of mesquite and carob pods"

~ ~

Prosopis pallida Ceratonia siliqua

Length (cm) 19.20 f 1.69 14.56 f 1.97* Width (cm) 1.57 f 0.12 1.82 f 0.16* Thickness (cm) 0.83 f 0.12 0.88 f 0.06* Pod weight (g) 11.98 f 1.79 14.91 f 2.32* Pulp weight (g) 10.93 f 1.80 12.95 f 2.35* Weight of seeds (9) 1.05 f 0.20 1.96 f 0.37* Number of seeds per pod 11.00 f 1.60* Moisture (g kg- ') (n = 6) 155.8 +_ 1.7*

Mean values f SD (n = 100). Mean values significantly differents *P < 0.05

25.48 f 3.53 100.9 f 0.1

(Student's t-test).

TABLE 2 Composition of Prosopis pallida and Ceratonia siliqua pods (g kg- DM)

Prosopis pallida" Ceratonia siIiquab

Pulp Total soluble sugars' 484.9 f 25.6 410-520 Reducing sugarsd 21.4 f 0.8 79-148 Total polysaccharides (NS + UA)e 217.8 f 5.2 126 Klason lignin 104.4 +_ 2.1 41 Total soluble polyphenols/ 8.2 f 0.1 13-38 Condensed tanninsg 4.1 f 0.3 164-179 Protein (N x 6.25) 81.1 k0.8 27742 Fat (light petroleum extraction) 7.7 f 1.2 5-1 1 Ash (SSOOC, 5 h) 36.0 f 1.7 27-33

Seeds Endosperm gum (galactose : mannose ratio) 1 : 1.36 1 : 3.35

a Experimental values. Mean f SD (n = 5).

Saura-Calixto et al(1991b) and Gaisford et a1 (1986). ' Anthrone-thiourea method (Southgate 1976).

Range of values. Data taken from (Saura-Calixto and Caiiellas (1982), Saura-Calixto (1988),

Automated neocuproine glucose method (Bittner and Manning 1966). NS, neutral sugars; UA, uronic acids. Folin-Ciocalteau's method (Montreau 1972).

9 HCl/BuOH treatment (Saura-Calixto 1988).

Composition and potential uses of mesquite pods 305

TABLE 3 Dietary fibre (DF) components and associated compounds (g kg-' DM) in mesquite and

carob pulps

Prosopis pallida" Ceratonia siliquab

Insoluble DF Neutral polysaccharides Acidic polysaccharides Klason lignin

Neutral polysaccharides Acidic polysaccharides

DF-associated compounds Condensed tannins Resistant protein Soluble polyphenols

Total D F Total insoluble fraction (fibre + associated compounds)

Soluble DF

306 174.7 f 4.6 26.9 f 0.6

104.4 f 2.1 16.2 7.7 f 0.8 8.5 f 1.5

3.3 f 0.4 22.0 f 1.3 0.8 f 0.1

322.2 348.3

139 91 7

41 28 13 15

171 18 9

167 365

Experimental values. Mean f SD ( n = 5) . Data taken from Saura-Calixto and Caiiellas (1982), and Saura-Calixto (1987; 1988).

Soluble sugars account for about 50% of the pulp. Sucrose is the main constituent of this fraction (95% of total sugars). Glucose, fructose, galactose and arabinose are minor constituents. A similar composition, with lower percentage of sucrose (70%) was reported for CS (Saura-Calixto 1987).

One of the main differences between both pods lies in their polyphenolic composition. PP contains an appre- ciably smaller amount of both soluble and condensed tannins than CS. The amounts of protein and dietary fibre in mesquite pods are higher than in CS.

The analysis of the indigestible dietary fibre residues of PP pulp revealed only small amounts of associated compounds (resistant protein and condensed tannins) (Table 3). In contrast, the original protein and con- densed tannins of CS pulp remained quantitatively in fibre residues (Saura-Calixto 1988).

Nutritional evaluation

PP pods are presently utilised very little, while CS is widely used as a source of either animal or human food.

By comparing the composition of the two pulps the following can be inferred.

0 Both materials are excellent sources of energy because of their high content of soluble sugars.

0 The protein content is higher in PP than in CS (Table 2). The digestibility of PP protein is higher than that of CS as well, only a small proportion of PP protein (27%) remains indigestible associated to fibre residues (resistant protein), while the per- centage of resistant protein of CS was 67% of the total protein (Saura-Calixto et a1 1991b) (Table 3). In uiuo studies performed with Wistar rats showed

TABLE 4 Potential uses of Prosopis pallida pods

Pulp Syrup (water extraction) Cacao substitute (roasting) Coffee substitute (flour, after partial removal of sugars) Sugar production (extraction, crystallisation) (Loo 1969) Ethanol production (fermentation) (Ancarani 1976) High dietary fibre (DF) material48% total DFdextract of soluble sugars and dry) High D F material enriched in soluble DF (as above and adding 10-20% of seed gum) Protein concentrate (fungal or bacterial inoculation) (Macris and Kokke 1977; Caiiellas et a1 1989) Animal feed (directly or mixed with other nutrients) (Meyer et a1 1986)

Gum from endosperm and protein concentrates from germ (in a single process) Seeds

306 L Bravo, N Grados, F Saura-Calixto

a good correlation between resistant protein in dietary fibre residues and protein excreted in faeces (Bravo et a1 1992, 1993). PP contain a significantly smaller amount of con- densed tannins and soluble polyphenols than in CS. The adverse effects of these antinutrients such as growth depression, decrease in protein digest- ibility and inhibition of digestive enzymes (Singleton 1981) are limiting aspects of the amount of CS pulp to be used in food products, while it should be less significant or negligible for PP pulp.

Potential uses

Table 4 summarises the proposed potential uses for mesquite pods, taking into account their composition and nutritional evaluation as well as the present uti- lisation of CS pods.

The Prosopis pallida gum could probably be used in the food industry similarly to guar and carob bean gums, although further studies into its physicochemical and rheological properties as food additives are needed. Nevertheless, the lower yield of gum per seed in PP pods when compared with CS (Table 1) should be taken into account for commercial purposes.

REFERENCES

Ancarani L 1976 La “ceratonia siliqua”: produzione, impieghi, commercio. Rass Chim 4 174-182.

Becker R, Sayre R N, Saunders R M 1984 Semiarid legume crops as protein resources. J Am Oil Chem SOC 61 931-938.

Bittner D L, Manning J 1966 Automated neocuproine glucose method : critical factors and normal values. Technicon Sym- posium 1 33-36.

Bravo L, Goiii I, Saura-Calixto F 1992 Effects of dietary fibre and tannins from apple pulp on the composition of faeces in rats. Br J Nutr 67 463-473.

Bravo J, Mafias E, Saura-Calixto F 1993 Dietary non- extractable condensed tannins as indigestible compounds: effects on faecal weight, and protein and fat excretion. J Sci Food Agric 63 63-68.

Caiiellas J, Pou J, Mulet A 1989 Protein enrichment of carob kibbles after sugar extraction. Lebensm Wiss Techno1 22

Englyst H N, Cummings J H 1988 Improved method for mea- surement of dietary fiber as non-starch polysaccharides in plant foods. J AOAC 71 804-814

Gaisford S E, Harding S E, Mitchell J R, Bradley T D 1986 A comparison between the hot and cold water soluble frac- tions of two locust bean gum samples. Carbohydr Polym 6

Loo T G 1969 Aspects of the isolation of sugar from Cera- tonia siliqua. Pub1 Royal Trop lnst 288, 11-12.

Macris B J, Kokke R C 1977 Kinetics of growth and chemical composition of Fusarium monilijorme cultivated on carob aqueous extract for microbial production. Eur J App l Microbiol4 93-99.

Meyer D, Becker R, Gumbmann M R, Vohra P, Neukom H, Saunders R M 1986 Processing, composition, nutritional evaluation, and utilization of mesquite (Prosopis spp.) pods as a raw material for the food industry. J Agric Food Chem

Montreau F R 1972 Sur le dosage des composes phknoliques totaux dans les vins par la mkthode Folin-Ciocalteau. Conn Vigne Vin 24 397-404.

Prosky L, Asp N-G, Schweizer T F, Devries J W, Furda I 1988 Determination of soluble, insoluble and total dietary fiber in foods and food products: interlaboratory study. J

Saura-Calixto F 1987 Determinacion de la composicion quimica de la algarroba (Ceratonia siliqua). Azucares, taninos, pectinas y aminoacidos. Anal Brornatol39 81-93.

Saura-Calixto 1988 Effect of condensed tannins in the analysis of dietary fibre in carob pods. J. Food Sci 53 1769-1771.

Saura-Calixto F, Caiiellas J 1982 Components of nutritional interest in carob pods (Ceratonia siliqua). J Sci Food Agric

Saura-Calixto F, Abia R, Clavijo G 1991a Caracteristicas quimicas del endocarpio del fruto del algarrobo piurano (Prosopis pallida). Bol SOC Quim Peru 57 245-250.

Saura-Calixto F, Gofii I, Mafias E, Abia R 1991b Klason lignin, condensed tannins and resistant protein as dietary fibre constituents : determination in grape pomaces. Food Chem 39 299-309.

Scott R W 1979 Colorimetric determination of hexuronic acids in plant materials. Anal Chem 51 936-941.

Singleton V L 1981 Naturally occurring food toxicants: phe- nolic substances of plant origin common in foods. Ado Food Res 27 149-242.

Southgate D A T 1976 Determination of Food Carbohydrates. Applied Science Publishers Ltd, London, UK.

73-77.

423-442.

34 914-919.

AOAC 71 1017-1023.

33 1319-1323.