Plant Foods for Human Nutrition 36:295-307 (1987) © Martinus Nijhoff/Dr W. Junk Publishers, Dordrecht - - Printed in the Netherlands

Soaking and cooking parameters of tepary beans: effects of cooking time and cooking temperature on hardness and activity of nutritional antagonists

SALAM A.R. KABBARA, ~ IBRAItlM R. ABBAS, JOSEPH C. SCHEERENS, ANN M. TINSLEY and JAMES W. BERRY

Department of Nutrition and Food Science, University of Arizona, Tucson, AZ 85721, USA I Present address for Ms S.A.R. Kabbara: 3524 W. Del Monte #4, Anahelim, CA 92804, USA

(Received April 18, 1986; accepted in revised form August 12, 1986)

Key words: tepary bean, bean hardness, scterema, antinutritionaI factor, lectin, chymotrypsin inhibitor, trypsin inhibitor

Abstract. Tepary samples were examined for patterns of hydration, dry matter losses during the processes of soaking and cooking, residual hardness in partially cooked samples and heat lability of endogenous proteinaceous antinutritional factors. At 24 °C, teparies imbibed water equivalent to their weight (100% hydration) in 4h and continued to absorb water rapidly for an additional 4 h before reaching an equilibrium hydration. During the processes of soaking and cooking, materials leached from raw beans represented 7.3 and 13.5 % of their dry weight, 4.3 and 12.4% of their protein content, 7.1 and 12.2% of their stored car- bohydrate and 22.4 and 33.4% of their mineral levels, respectively. In samples prepared at different cooking times (60, 90, 120, 150, 180min) and cooking temperatures (80, 85, 90, 95 °C), longer times and higher temperatures resulted in greater reductions in residual bean hardness; interactive effects of time and temperature treatments were significant. Residual activity of trypsin and chymotrypsin inhibitors in partially-cooked samples appeared to be negligible. In addition, at least 80 % of the original hemaglutinating activity of lectins in raw beans was lost during partial-cooking of samples under all cooking regimes.

Introduction

Tepa ry bean (Phaseolus acutifolius var. latifolius) is a nat ive legume o f southwes tern N o r t h Amer ica . The ag ronomic proper t ies o f t epary beans have been descr ibed by F r e e m a n [6], who cons idered them as a d rough t - adap ted , d isease-res is tant crop. Domes t i ca t ed variet ies have been t rad i - t ional ly g rown by the P a p a g o and P ima Ind ians for centuries. Tepar ies have been r epor t ed to yield seeds in quant i t ies exceeding 4600 K g / h a with supplementa l i r r iga t ion [10]. However , harves t weights o f 500-1000 K g / h a have been more c o m m o n l y repor ted [2, 3, 25, 38]. Tepar ies typical ly con ta in 23% crude prote in , a fac tor which is affected by the intensi ty o f water stress; levels o f p ro te in in t epary samples range f rom 13-29% [24, 30].

The poten t ia l o f t epary beans as a food source for people o f Afr ican and Midd le Eas tern regions has been par t i a l ly evalua ted [35]. Organo lep t i c eva lua t ion o f Niger ian and Saudi A r a b i a n food p roduc t s fo rmula ted with

296

teparies as a substitute for beans commonly used in these regions indicated dishes to be moderately to highly acceptable. The analysis of uncooked tepary samples for anti-nutritional factors revealed levels of flatulent oligosaccharides, trypsin inhibitors and phytic acid similar to those asso- ciated with other grain legumes. However, in comparison to other grain legumes, lectin levels uncovered in tepary samples were uncommonly high. Fully-cooked samples of beans exhibited substantially reduced levels of most nutritional antagonists. High levels of heat-labile proteinaceous antagonists were previously reported in both white seeded and brown seeded tepary varieties [34].

Tepary beans, like many other legumes, require a long cooking time. This attribute, coupled with high levels of nutritional antagonists, limit their usefulness in fuel-poor, arid areas [35]. Two factors inducing hard- ness in beans have been described [8]: hard shell (seed coat impermeability) and scelerma, a condition whereby cotyledons are unable to imbibe water even though barriers of the seed coat have been removed. Snyder [32] demonstrated the independent action of these two physical/physiological conditions.

If teparies are grown in fuel-poor areas, the probability for their con- sumption in a partially cooked state may be high. Possible nutritional consequences of consuming partially cooked teparies have not heretofore been assessed. The present study has been undertaken to illustrate the following: patterns of water absorption in soaked beans; relationships among cooking time, cooking temperature and bean hardness (sclerema); and heat-lability of proteinaceous nutritional antagonists in partially- cooked beans. In addition, the composition of soaking and cooking liquors was examined.

Materials and methods

Materials

Tepary beans, (a white seeded variety) donated by a commercial producer (W.D. Hood), were grown and harvested in Coolidge, AZ during the summer of 1982. They were subsequently stored in sealed containers at room temperature for at least 1 yr prior to use to exacerbate the hardness phenomenon [17].

Water absorption pattern

Tepary beans (20g) were soaked with 100ml of deionized water for different time intervals (from 0.5-24.0 h). Beans were occasionally stirred. The slurry was decanted and the beans were weighed. The absorption pattern was established by plotting time vs. weight of hydrated beans.

297

Examination of soaking and cooking liquors

Tepary beans (200 g in duplicate) were soaked at room temperature in 11 of deionized water for 12 h with continuous stirring. The soaking liquor was filtered through sintered glass and the volume of the clarified liquid was measured. Three 50 ml aliquots were transferred to previously dried, accurately weighed beakers for quantitative determination of total dissol- ved solids. The remainder of the liquor was freeze-dried and used in subsequent analysis of proximate composition.

Additional samples of teparies (200 g in duplicate) were soaked as described above. After removal of the soaking liquor, the beans were resubmerged in an additional 11 ofdeionized water and boiled for a period of 4 h, removed from the heat source and cooled to room temperature. The cooking broth was screened through a 60-mesh sieve and then standar- dized to 600 ml with deionized water. Three 25-ml aliquots were taken for the quantitative determination of total dissolved solids. The remainder of the liquid was prepared for proximate analysis as above.

Dissolved solids of soaking and cooking liquors were determined gravimetrically after oven-drying. Crude protein levels were quantified using the micro Kjeldahl method. Levels of additional components were obtained using the following techniques: ash by combustion of sample at 525 °C; crude fiber by the acid detergent method of Van Soest [36]; and carbohydrates (starch and free sugars) by colorimetry after combination with anthrone and sulfuric acid [4]. All analyses (except determinations of dissolved solids) were performed in duplicate.

Preparation of partially-cooked samples

Water (approximately 1600 ml held in duplicate 21 beakers) was preheated to the desired temperature on a hot plate controlled using a Dynapac-10 proportional temperature controller (Dynatronic Instruments Inc., Chica- go, IL). Temperature fluctuations in the liquid were minimized by sur- rounding the cooking vessels with a fiberglass sleeve and covering them with a fiberglass-filled pillow. The system was allowed to equilibrate 2-3 h prior to use.

Beans were prepared under sub-optimal cooking conditions (i.e. shor- tened soaking time, reduced cooking times and temperatures) to obtain partially cooked samples exhibiting various degrees of residual hardness and raw bean flavor. Duplicate groups of approximately 200 beans were pre-soaked in deionized water for 30 min, drained, and spread on paper towels for 3 min to dry bean surfaces. Groups were then resuspended in hot water, transferred to the pre-equilibrated cooking liquor, and cooked at one of four temperatures (80, 85, 90 and 95 °C) for one of five time intervals (60, 90, 120, 150 and 180min). After the cooking period, the

298

,0F /

2 0 ~ I .......... I [ I I I [ I I I I I I 0 4 8 12 16 20 24

SOAKING TIME (H)

Figure I. Hydration rate of tepary beans soaked at 24 °C.

cooking broth was drained and the beans were rinsed with cold water and allowed to reach room temperature. The relative hardness of partially- cooked beans was measured using 50 seed samples of each cooking repli- cate; the remainder of each replicate (approximately 150 beans) was frozen and lyophilized prior to evaluation for residual levels of proteinaceous nutritional antagonists.

Determination of bean hardness in partially-cooked samples

Bean seed coats were removed manually prior to determination of residual compressive strength in the cotyledon. The force necessary to fracture beans was measured with a Hunter Spring Force Gage (Hunter Spring Div., Hatfield PA); values were reported as duplicate means of 50 deter- minations [17].

Determination of antinutritionalfactor levels in raw and partially-cooked samples

Raw beans and lyophilized samples of partially-cooked beans were ground to pass through a 30 mesh screen, defatted with hexane on a Goldfisch apparatus (4 h extraction) and pulverized with a mortar and pestle. Trypsin inhibitor levels were quantified by the method of Kakade et al. [18] with minor modifications similar to those suggested by Hammer-

299

strand et al. [9,1 7]. Extracts containing inhibitors were added to solutions containing trypsin and benzoyl-DL-arginine-p-nitroanilide hydro- chloride; mixtures were incubated for precisely 10min. The amount of trypsin inhibition in incubated solutions was proportional to the decrease in absorbance of the trypsin-cleaved product (p-nitroanilide hydro- chloride) at 410nm. Replicates of spectrophotometer readings were av- eraged. Chymotrypsin inhibitor levels in pulverized materials were quan- tified in a similar manner. Spectrophotometric analysis (280 nm) of in- cubated extracts reflected the level of chymotrysin inhibition through reduced chymotrypsin cleavage of a casein substrate [28]. Values for digestive enzyme inhibitors were reported as trypsin or chymotrypsin inhibitor units (TIU/mg sample or CIU/mg sample) [18]. The semi-quan- titative microtitration method of Jaffe et al. [16] was used to estimate lectin levels in pulverized samples. Serial dilutions of sample extracts in normal saline were incubated with protease-treated rabbit red blood cells (previously found to be most responsive [34]) in multi-well microtitration plates; activity of lectins was equated with titer levels of the ultimate dilution effecting hemagglutination.

Results and discussion

Water absorption pattern

The pattern of water absorption by tepary beans is displayed in Figure 1. The hydration coefficient [ratio (w/w) of soaked vs dry beans] was ap- proximately 2.2 after 24 h of soaking. Beans absorbed water in quantities equivalent to their weight (100% hydration) in approximately 4h; they continued to imbibe water rapidly for an additional 4 h. Similar hydration coefficients and patterns of water absorption were exhibited by soybeans [39]. However, teparies appeared to surpass various strains of common bean (Phaseolus vulgaris L,) in their capacity for water absorption [7, 11, 12]. In the latter species, the rate of hydration was shown to be tem- perature dependent [27].

Examination of soaking and cooking liquors

Respectively, soaking and cooking liquors were determined to contain 1.9 and 4.2% total dissolved solids which resulted from the loss of 7.3 and 13.5% of the original dry weight of the bean (Table 1). By discarding both soaking and cooking liquors, one might expect to lose approximately 17% of the original protein, nearly 20% of the original carbohydrates and over 55% of the original mineral levels found within the raw beans.

Soaking liquors are traditionally discarded as they often contain high levels of flatulent sugars and other deleterious compounds [21], Of the material recovered from soaking liquors, over one-half was determined to be free sugars which represented about 7% of the carbohydrate present in

Tabl

e 1.

Com

posi

tion

of

raw

tep

ary

bean

s an

d di

ssol

ved

soli

ds in

the

ir s

oaki

ng a

nd c

ooki

ng l

iquo

rs ~

Sou

rces

C

om

po

nen

t

Dis

solv

able

C

rude

C

rude

D

iges

tibl

e C

arbo

hydr

ates

C

rude

A

sh

Oth

er c

soli

ds

prot

ein

fat

Tot

al b

Sta

rch

Sug

ar

fibe

r

Raw

bea

ns d

(g c

omp.

/100

g b

eans

) 20

.8

23.2

0.

8 59

.0

,e

, 6.

5 4.

4 *

Dis

solv

ed s

olid

s ¢

in s

oaki

ng l

iquo

r (g

com

p./1

00 g

sol

ids)

10

0.0

13.3

*

57.5

0.

3 57

.2

* 13

.5

15.7

D

isso

lved

sol

ids e

in

soa

king

liq

uor

(g c

omp.

/100

g b

eans

) 7.

3 1.

0 *

4.2

0.2

4.2

* 1.

0 1.

1 P

ropo

rtio

n (%

) of

* co

mpo

nent

lea

ched

fr

om r

aw b

eans

(g

los

t/g

orig

. pr

esen

t)

35.1

4.

3 *

7.1

* *

* 22

.4

* D

isso

lved

sol

ids f

in

coo

king

liq

uor

(g c

ornp

./10

0 g

soli

ds)

100.

0 21

.3

* 53

.7

9.5

44.2

1.

0 10

.9

l 1.9

D

isso

lved

sol

ids g

in

coo

king

liq

uor

(g c

omp.

/100

g b

eans

) 13

.5

2.9

* 7.

3 1.

3 6.

0 0.

2 1.

5 1.

6

Pro

port

ion

(%)

of*

com

pone

nt le

ache

d fr

om r

aw b

eans

(g

los

t/g

orig

. pr

esen

t)

64.9

12

.4

* 12

.2

* *

3.0

33.4

Pro

port

ion

(%)

of

com

pone

nt le

ache

d fr

om r

aw b

eans

(T

otal

) (g

los

t/g,

ori

g. p

rese

nt)

100.

0 16

.7

19.3

3.

0 55

.8

"Bea

n sa

mpl

es a

naly

zed

as is

; soa

king

liqu

or f

rom

sam

ples

soa

ked

for

12 h

at r

oo

m te

mpe

ratu

re; c

ooki

ng li

quor

fro

m s

ampl

es c

ooke

d fo

r 4

h in

boi

ling

wat

er.

b In

raw

bea

n sa

mpl

es, t

otal

car

bohy

drat

e ca

lcul

ated

by

diff

eren

ce;

in d

isso

lved

sol

ids,

tot

al c

arbo

hydr

ate

calc

ulat

ed f

rom

val

ues

dete

rmin

ed b

y st

arch

and

su

gar

anal

ysis

. c I

n di

ssol

ved

solid

s, o

ther

cal

cula

ted

by d

iffe

renc

e.

dFor

raw

bea

ns,

data

pre

viou

sly

repo

rted

in

[30]

. e

Whe

re a

ppro

pria

te,

no

t de

term

ined

, no

t ca

lcul

ated

, n

ot

appl

icab

le o

r be

low

lim

its o

f de

tect

ion.

f

Det

erm

ined

by

anal

ytic

al p

roce

dure

. gC

alcu

late

d w

ith

resp

ect t

o pe

rcen

tage

dry

wei

ght

of

bean

s w

hich

was

sol

uble

dur

ing

soak

ing

or c

ooki

ng:

(e.g

. cr

ude

prot

ein)

13.3

g p

rote

in/1

00 g

sol

ids

× 0

.073

sol

ids/

100

g be

ans

=

1.0

g pr

otei

n/10

0 g

bean

s.

h Cal

cula

ted

wit

h re

spec

t to

per

cent

age

of

com

po

nen

t or

igin

ally

pre

sent

in

dry

bean

s: (

e.g.

cru

de p

rote

in)

[1.0

g l

each

ed f

rom

100

g b

eans

/23.

2 g

orig

inal

ly p

rese

nt i

n be

ans]

×

100

=

4.3%

pro

tein

lea

ched

. ~C

alcu

late

d w

ith

resp

ect

to p

rop

ort

ion

of

com

po

nen

t lo

st d

urin

g th

e so

akin

g an

d co

okin

g pr

oces

ses

com

bine

d (e

.g.

crud

e pr

otei

n)

4.3%

ori

gina

lly p

rese

nt-l

ost d

urin

g so

akin

g +

12

.4%

ori

gina

lly

pres

ent-

lost

dur

ing

cook

ing

=

16.7

% o

rigi

nall

y pr

esen

t-lo

st in

soa

king

and

coo

king

liqu

ors.

302

300 F 80" / oo\ 25ol- \ ~ 8~ o

OOl- X \ ~ 150

/ \

5O

o I I I ....... I I 6o 90 ~z0 ~5o ~ao

T I M E (min)

Figure 2. Residual compressive strength (g) of beans cooked at various times and tem- peratures.

the raw beans. This process also extracted a modest portion of the protein content of the bean (approximately 4%). However, cold water-soluble starch could not be detected. A substantial portion of the original mineral content of the beans (22.4%) was presumed to have been leached during the soaking process. Losses of soluble components during soaking has been reported for seeds of other legume species [5, 20, 31, 39]. In soybeans, as much as 1.7% of the original protein and 40% of the original flatulent oligosaccharides were extracted into the soaking liquor [39] whereas solid losses during the soaking process were reported to exceed one-third of the dry weight of common bean under certain conditions [20]. The extent of leaching in both soybean and common bean was highly dependent upon the temperature during the soaking process.

In contrast, cooking broths are often retained in the product consumed or, in underdeveloped regions, they are fed to infants. Broths could be expected to contain approximately 13 % of the original solid weight of the raw beans. Of this material, over 20% is protein, over 10% is composed

303

of minerals, over 44% is sugar, and nearly 10% is hot water-soluble starch. The cooking process was estimated to remove nearly twice as much carbohydrate material than does the soaking process (12,2% vs. 7.1%, respectively). Ash content in cooking liquor was substantial and when mineral losses during this process were combined with losses occurring during the soaking process, they represented over one-half of the mineral content of the dry bean. In many areas, legumes are considered to be an important source of required minerals such as calcium, phosphorus and iron. Therefore, the advantages of discarding liquors may be somewhat offset by detrimental nutritional consequences.

Effect of cooking time and cooking temperature on bean hardness

The application of increasing amounts of compressive force to cooked beans most often resulted in their instantaneous cleavage upon reaching a critical force level. Unfortunately,equipment used for this determination was incapable of cleaving raw beans at the maximum force levels designed to be applied by the instrument [7].

In general, increased cooking time resulted in decreased hardness in partially-cooked beans (Figure 2). However, the magnitude of these effects varied with respect to temperature treatment. At 90 and 95 °C, statistically significant decreases in hardness were observed among samples cooked from 60 to 120rain. Longer cooking times failed to produce drastic differences in bean hardness, but since samples cooked 120 min or longer still retained the starchy, raw-bean flavor, they were still considered to be partially-cooked (see discussion below). Increases in cooking time had less effect upon the hardness of beans cooked at 85 °C and almost no effect upon beans cooked at 80 °C. With prolonged cooking under these con- ditions, it is doubtful that an edible product can be obtained; beans cooked in this manner appear to reach a plateau in the softening process which can only be overcome by increased cooking temperature.

Among samples cooked for a given period of time (e.g. 60 rain), mean values for bean hardness were significantly lower (with few exceptions) in samples as they were cooked at successively higher temperatures. Differen- ces in hardness of partially-cooked beans were greatest when samples were cooked for 150 min or longer.

Cookability of tepary and other beans

Bean cookability and/or the texture of the cooked product has been found to be influenced by a number of factors including: variety [11, 12, 23], growing conditions [14, 31, 37], moisture content of the stored bean [1, 19, 23, 31], chemical composition [22] and pretreatment by soaking in water or salt solutions [13, 20, 22, 29, 37, 40]. These factors may modify cooka- bility in beans by altering physical and chemical relationships of cellular and intercellular constituents (e.g. changes in morphology, the content of

304

Table 2. Effects of cooking time and cooking temperature on trypsin and chymotrypsin inhibitor activity in partially-cooked tepary samples a'b'c

Inhibitor Cooking time (rain)

Cooking temperature (°C)

80 85 90 95

Trypsin 60 9.2 2.3 1.8 1.7 inhibitor 90 2.8 2.3 2.6 3.1

120 2.0 1.3 3.1 3.4 150 2.1 2.1 2.5 2.0 180 1.7 2.3 2.5 2.9

Chymotrypsin 60 2.1 1.8 ,d , inhibitor 90 1.8 1.9 * *

a Tabular values represent the mean TIU/mg sample or CIU/mg sample for duplicate extractions; one TIU (CIU) is defined as a decrease in trypsin (chymotrypsin) activity resulting in a decrease in 0.01 absorbance units per 10 ml of reaction mixture compared with the absorbance of the 10ml sample blank. b Activity of trypsin inhibitor and chymotrypsin inhibitor in raw beans = 17.3 TIU/mg sample and 14.0 CIU/mg sample respectively. For values of trypsin inhibition, mean value of sample cooked at 80 °C for 60 rain signifi-

cantly higher than all others. a Values not determined.

minerals, protein and organic phosphorus compounds, and enzymatic activity) which may ultimately influence the rate of hydration, hydrogen bond disruption and other phenomenon associated with the process of cooking.

Neithammer [26] maintained that although tepary cooking time may vary depending on freshness, variety, location of production and/or on other unknown factors, it can be assumed that they will require a longer period to cook than other bean species commonly consumed in the U.S.A. Effects of storage conditions, pretreatment, and methods of preparation upon cookability and nutritional/organoleptic quality of teparies are cur- rently being studied.

The practical significance of the information reported herein lies not in the force values reported or in its contribution to the general understand- ing of the physical/chemical nature of the hard to cook phenomenon, but rather in the demonstration of interaction between the two cooking par- ameters and their effects upon bean hardness and the disappearances of proteinaceous antinutritional factors (see discussion below). Beans may never be purposely cooked at constant temperatures below that of boiling water. However, in fuel-poor, desertified areas where the introduction of teparies has been proposed [35], beans may be subjected to a variety of temperatures during the cooking process. It is under these conditions that the interaction of time and temperature upon cookability of the teparies may be of considerable importance to the nutritional and organoleptic quality of the consumed product. When teparies are consumed in areas where fuel is plentiful, they will most likely be simmered for several hours

305

Table 3. Residual activity of lectins in partially-cooked tepary samples "bx

Time (min) Temperature

80 85 90 95

60 2560 160 80 10 90 5120 136 160 10

120 528 128 128 224 150 1032 96 96 224 180 1088 80 144 22

a Values represent mean titer values of last serial dilution capable of agglutinating protease- treated rabbit red blood cells: Titer values = 2 ~, where n represents the mean number (integer or decimal fraction) of the last well exhibiting evidence of hemagglutination. bThe mean titer value for raw tepary samples = 24,576.

after they become soft. Beans will be considered "cooked" only when those starchy, beany flavors associated with the uncooked seed are lost. The cooking time required for the transition to organoleptic acceptability will be of little concern.

Heat stability of proteinaceous antinutritional factors

Mean values for residual trypsin inhibitor activity in partially-cooked samples are displayed in Table 2. No statistical differences among treat- ments existed except for the sample prepared at 80 °C for 60 min. This sample still possessed a modest level of trypsin inhibitor activity. All other treatment combinations were considered adequate to denature this pro- teinaceous nutritional antagonist long before beans were softened. These results strongly suggested the trypsin inhibitors of tepary bean to be heat labile, even under modest heat treatments. The trypsin inhibitor activity found in raw tepary beans (17.3 TIU/mg sample) and in partially-cooked samples (1.29 3.42TIU/mg sample, excluding the exceptional sample discussed above) agreed closely with values previously reported by Thorn and coworkers [34]. However, the extent of trypsin inhibitor activity in partially-cooked samples of this study was substantially lower than those published by Tinsley et al. [35] for fully-cooked samples.

Chymotrypsin inhibitor activity in raw tepary beans (14.0CIU/mg sample) has not been reported previously. However, an examination of partially-cooked samples suggested this nutritional antagonist to be more heat labile than its trypsin inhibitor counterpart. Results indicated little activity even when bean samples were prepared at 80 °C for only 60 min.

All cooking treatments reduced lectin activity by at least 80% of that displayed by raw bean samples (Table 3). In general, as with the other proteinaceous antinutritional factors studied, increased cooking time and cooking temperature resulted in decreased hemagglutination response. Samples cooked at temperatures of 85 °C or greater demonstrated only 0.04-0.90% of the original activity present. Similarly, the heat-labile nature of tepary lectins was previously reported by other authors [34, 35].

306

Although agglutination ability of partially-cooked tepary samples is dras- tically reduced from that displayed by raw beans, levels of activity present may still pose nutritional problems. The levels of activity remaining in most samples after heat treatment were nearly as great as values found in raw samples of other legumes [33, 34, 35]. The nutritional significance of lectin activity in these foodstuffs is further complicated by the imperfect relationship of hemagglutinating ability and toxicity. Jaffe [15] reported quantitative differences in agglutinating strength and toxicity among bean varieties within a species. Due to the ambiguity of this relationship, there appears to be no published precedent for determining safe levels of re- sidual lectin activity.

References

1. Albrecht WJ, Mustakas GC, McGhee JE (1966) Rate studies on atmospheric steaming and immersion cooking of soybeans. Cereal Chem 43:400

2. Bouscaren J, Waines JG, Boykin-Bouscaren LA (1983) Cultivation and use teparies in Sonora, Mexico. Desert Plants 5:38

3. Burgess MA (1983) The tepary connection: a visit with WD Hood. Desert Plants 5:3 4. Clegg KM (1956) The application of the anthrone reagent to the estimation of starch in

cereals. J Sci Food Agric 7:40 5. Ekpenyong TE, Borchers RL (1980) Effect of cooking on the chemical composition of

winged beans (Psophocarpus tetragonolubus). J Food Sci 45:1559 6. Freeman GF (1913) Tepary, a new cultivated legume from the Southwest. Bot Gaz

56:395 7. Ghaderi A, Hosfield GL, Adams MW, Uebersax MA (1984) Variability in culinary

quality, component interrelationships, and breeding implications in navy and pinto beans. J Amer Soc Hort Sci 109:85

8. Gloyer WO (1921) Sclerema and hard shell, two types of hardness of the bean. Proc Assoc Off Seed Anal I3:60

9. Hammerstrand GE, Black LT, Glover JD (1981) Trypsin inhibitors in soy products: modification of the standard analytical procedure. Cereal Chem 58:42

10. Hendry GW (1919) Bean Culture in California. CA Agr Exp Sta Bulletin 294 11. Hosfield GL, Uebersax MA (1980) Variability in physico-chemical properties and nutri-

tional components of tropical and domestic dry bean germplasm. J Amer Soc Hort Sci 105:246

12. Hosfield GL, Uebersax MA, Isleib TG (1984) Seasonal and genotypic effects on yield and physico-chemical seed characteristics related to food quality in dry, edible beans. J Amer Soc Hort Sci 109:182

13. Iyer V, Salunkhe DK, Sathe SK, Rockland LB (1980) Quick-cooking beans (Phaseolus vulgaris L.) h investigations on quality. Qual Plant Plant Foods Hum Nutr 30:27

14. Jackson GM, Varriano-Marston E (1981) Hard to cook phenomenon in beans: effects of accelerated storage on water absorption and cooking time. J Food Sci 46:799

15. Jaffe WG (1975) Factors affecting the nutritional value of beans. In: Milner M, (ed.) Nutritional Improvement of Food Legumes by Breeding. John Wiley and Sons, New York

16. Jaffe WG, Brucher O, Palozzo A (1972) Detection oftbur types of specific phytohemag- glutinins in different lines of beans (Phaseolus vulgaris). Z Immun Forsch Bd 142:439

17. Kabbara S (1985) Effect of Cooking Time and Temperature on Hardness and Antinutri- tional Factors of Tepary Bean. Thesis, University of Arizona, Tucson

18. Kakade ML, Rackis JJ, McGhee JE, Puski G (1974) Determination of trypsin inhibitor activity of soy products: a collaborative analysis. Cereal Chem 51:376

19. Kon S (1968) Pectic substances of dry beans and their possible correlation with cooking time. J Food Sci 33:437

307

20. Kon S (1979) Effect of soaking temperature on cooking and nutritional quality of beans. J Food Sci 44:1329

21. Liener IE (1962) Toxic factors in edible legumes and their eliminations. Amer J Clin Nutr 11:28

22. Matson S (1946) The cookability of yellow peas. Acta Agric Suec 1:185 23. Morris HJ, Olson RL, Bean RC (1950) Processing quality of varieties and strains of dry

beans. Food Tech 4:247 24. Nabhan GP, Berry JW, Anson C, Weber CW (1980) Papago Indian floodwater fields and

tepary bean protein yields. Ecol Food Nutr 10:71 25. Nabhan GP, Felger RS (1978) Teparies in southwestern North America, a biogeographi-

cal and ethnohistorical study of Phaseolus aeutifolius. Econ Bot 32:3 26. Niethammer C (1983) Tepary cuisine. Desert Plants 5:8 27. Quast DG, daSilva SD (1977) Temperature dependence of hydration rate and effect of

hydration on the cooking rate of dry legumes. J Food Sci: 42:1299 28. Rick W (1974) Analysis ofchymotrypsin inhibitors. In: Berymeyer HU (ed) Methods of

Enzymatic Analysis. Academic Press, New York 29. Rockland LB, Jones TF (1974) Scanning electron microscope studies on dry beans:

effects of cooking on the cellular structure of cotyledons in rehydrated large lima beans. J Food Sci 39:342

30. Scheerens JC, Tinsley AM, Abbas IR, Weber CW, Berry JW (1983) The nutritional significance of tepary bean consumption. Desert Plants 5: I 1

3 I. Sefa-Dedeh S, Stanley DW, Voisy PW (1979) Effect of storage time and conditions on the hard-to-cook defect in cowpeas (Vigna unguieulata). J Food Sci 44:790

32. Snyder EB (1936) Some Factors Affecting the Cooking Quality of the Pea and Great Northern Types of Dry Beans. NE Agr Exp Sta Bulletin 85

33. Sotelo-Lopez A, Hernandez-Infante M, Artega-Cruz ME (1978) Trypsin inhibitors and hemagglutinins in certain edible leguminosae. Arch Invest Med 9:1

34. Thorn KA, Tinsley AM, Weber CW, Berry JW (I983) Antinutritional factors in legumes of the Sonoran Desert. Ecol Food Nutr 13:251

35. Tinsley AM, Scheerens JC, Alegbejo JO, Adan FH, Krumhar KC, Butler LE, Kopplin MJ (1985) Tepary beans (Phaseotus acutifolius var. latifolius): a potential food source for African and Middle Eastern cultures. Qual Plant Plant Foods Hum Nutr 35:87

36. Van Soest PJ (t963) Use of detergents in the analysis of fibrous feeds II: a rapid method for the determination of fiber and lignin. J Assn Off Agr Chem 46:829

37. Varriano-Marston E, Jackson GM (1981) Hard to cook phenomenon in beans: struc- tural changes during storage and inbibition. J Food Sci 46:1379

38. Wains JG (1978) Protein contents, grain weights, and breeding potential of wild and domesticated tepary beans. Crop Sci 18:587

39. Wang HL, Swain EW, Hesseltine CW, Heath HD (1979) Hydration of whole soybeans affects solids losses and cooking quality. J Food Sci 44:1510

40. Wilson JG, Uebersax MA, Hosfield GL, Zabik ME (1986) Assessment of processed bean textural quality. Presented at 46th Ann Meeting of the Institute of Food Technologists, Dallas, TX (USA) June 15-18.