EFFECT OF CONTROLLED FERMENTATION OF SOME TRADITIONAL FOODS ON THE GLYCAEMIC RESPONSE OF DIABETIC ADULT RATS

ABSTRACT

Effect of controlled fermentation with Candida tropicalis on glycaemic index of cassava, maize and sorghum flours and blood glucose response, protein utilization, mineral and vitamin bioavailability of their blends in diabetes induced adult rats was studied. Candida tropicalis was isolated and used in semi-solid state controlled fermentation of the starchy foods at 0, 24, 48 and 72h. Physicochemical composition of the fermented starchy flours and two under-exploited unfermented legume seed flours of Bielschmeidia gabonensis (BG) and Cola gigantean (CG) used as soup thickeners were determined. Standard techniques and statistical methods were adopted to generate data, separate and compare means of preliminary results. Three diets based on 24h fermented cassava (CA24h), maize (MA24h),  sorghum (SO24h) and unfermented  Cola gigeantea (CG) were used for the rat study. These test diets provided 1.6g nitrogen daily and 20g total dietary fibre/1000kcal in a ratio of 1:2, soluble: insoluble dietary fibre to mimic traditional diets. Rat chow (RC) served as the control. Sixteen adult rats (160-196g) were allotted to both control and 3 test diets in groups of 4 on the basis of body weight. The rats were individually housed in metabolism cages, induced diabetes with streptozotocin and fed ad libitum in a14-day balance study. Food intake, body weight, fasting blood glucose (FBG), plasma proteins, blood urea nitrogen (BUN), carcass nitrogen (CN), liver composition, protein, vitamin and mineral bioavailability were determined. All analyses were done using standard  techniques  to generate  data.  Completely  randomized  design was adopted  for the bioassay.  Students’  t-test,  Duncan’s  new multiple range test and Fisher’s least significant difference test were employed to separate and compare means statistically (p<0.05). CG had significantly (p<0.05) lower GI (68.30% versus 85.82), Ca and Fe and significantly (p<0.05) higher oxalate than BG (13.86g versus trace). The CA24h, MA24h, SO24h  flours had the best chemical value for viscosity (4.21cps, 2.49cps and 3.01cps, respectively), TDF (6.24%, 6.36% and

5.69%, each); TS (67.17%, 56.35% and 56.96%, each) and GI (44.01%, 47.43% and 46.68%, respectively). These GI values were significantly

(p<0.05) lower relative to their controls (93.06%, 94.76% and 84.66%, respectively). Calcium (Ca), zinc (Zn), magnesium (Mg) and riboflavin in fermented flours increased significantly (p<0.05) while Iron (Fe) significantly (p<0.05) decreased relative to the controls (0.64-0.73mg versus

0.0-0.40mg). Test diets had significantly (p<0.05) high oxalate relative to the safe level (3.75g versus 6.0g, 8.0g and 11.5g for CA24h  CG, MA24hCG and SO24hCG, respectively). Test diets significantly (p<0.05) reduced blood glucose (BG) in all groups of rats (420-465mg/100ml to

82.0-83. 50mg/100ml). N balance was positive for all groups of rats. Rats fed MA24hCG diet had significantly (p<0.05) higher food intake and biochemical profile over those of both control and other test diets. Thiamin, riboflavin and niacin retentions were negative for all rats (-0.003 to

-0.012mg; -0.40 to -0.88mg and -39.22 to -53.25mg, respectively). Calcium retention was positive for both test and control diets (101.89mg –

188.80mg). Mg retention was positive for CA24hCG (4.12mg) and MA24hCG (5.48mg) test diets alone. Fe retention was negative for all the groups (-30.35 to -68.07mg). Zn content of the diet was negligible, as well as in the metabolic waste. Candida tropicalis fermentation reduced GI of the traditional high GI starchy staples from 84-94% to 45-47%. C. gigeantea had lower GI than B. gabonensis. The novel diets based on blends of these low GI starchy flours and Cola gigeantea (a leguminous soup thickener) (in 1:2  ratio of soluble to insoluble dietary fibre) produced high dietary fibre diets which attenuated the high blood glucose in diabetic adult rats but compromised their protein utilization as well as mineral and vitamin balance. Further investigations on diabetic rats fed varying ratios of these low GI fermented traditional starchy staples and Cola gigeantea are needed to clearly establish safer levels of the blends with regard to food intake, weight loss and glycaemic control.

CHAPTER ONE

1.1      Background to the study

INTRODUCTION

Food is fundamental to human survival and constitutes a form of cultural expression. A people’s culture has a lot of influence on the kind of foods they eat and how they eat them. Hence, the term traditional foods, has been adopted to describe all foods from a particular culture, available from local sources and culturally acceptable as appropriate and desirable foods (Kulhnlein & Receveur, 1996). These traditional foods are often used in nutritional sciences as basis for ensuring and optimizing the  utilization of indigenous foods and their health benefits by individuals, households and communities. Traditional foods are obtained from two main sources; namely plant and animal sources.

Plant foods have remained the ultimate source of nutrients for larger population of the world.  Plant  materials  are  used  for  socio-cultural,  diabolic,  nutritional  and  therapeutic purposes. The global concern for the diversification of the uses of plant  foods to improve normal and therapeutic  nutrition has shifted  scientists’  interest to  enhancing the potential sources   of   beneficial   constituents   in   plant   foods.   One   approach   is   through   food biotechnology. Food-enhancing biotechnology has challenged scientists to integrate it within their  own  research  and  innovative  systems,  in  accordance  with  their  local  needs  and priorities. In this regard, Tagwireyi (2003) posits that the potential of biotechnology exists in sub-Saharan Africa if it can be adapted to the prevailing diet-related problems in the region.

A variety of plant foods (maize, rice, sorghum, millet, yam, cassava, cocoayam and legumes) are mainly produced as subsistence food crops in Africa. They are more commonly and widely consumed in Nigeria and other developing countries than in the developed world. They are also  relatively  cheap  and contribute  appreciably  to the  nutrient  intake (energy, protein, fat, vitamins and minerals) of the less developed world. In Nigeria, starchy staples (cereals, roots/tubers) and legumes constitute the  major part of the traditional diets, up to

70% and 25%, respectively. However, while cereals are the major staples in the north with higher intake of animal protein sources (mutton, beef and milk), starchy roots and tubers are the main staples in the south with relatively more consumption of legumes (Maziya-Dixion et al., 2004).

A comprehensive  review of available  information  on the nutritional  and  chemical composition of indigenous plant foods consumed in Nigeria has been published (Osagie & Eka, 1998). The results from the various researchers on plant foods focused mainly on their nutrient and anti-nutrient contents. Nevertheless, there is still much to be learnt about some of the non-nutrient components of the traditional plant foods. The full exploitation of a plant material for normal and therapeutic purposes may not be realized until the potentials of the plants are properly elucidated.

Despite the presence of anti-nutrients in raw foods, foods of plant origin also contain many bioactive compounds, which are not regarded as nutrients, but have possible benefits to human health. These include phytochemicals and dietary fibre, which are found naturally and abundantly in all plant foods. Phytochemicals  are generally defined  as naturally occurring components  of  plants  that  have  physiological  effects  in  humans  beyond  the  traditional nutrients they contain (Liu, 2004; Nyam News, 2005). They act as natural defense systems for  their   host  plants  and  also  provide   colour,   aroma  and  flavor  (McCarty,   2004). Phytochemicals’ direct antioxidant activity as well as modulation of enzyme expression or

hormone activity, contribute to their disease-preventing effects and protection from vascular diseases and many cancers in particular (McCarty, 2004).

Dietary fibre, on the contrary, consists of a heterogeneous  mixture of  non-starchy polysaccharides  (NSP)  (Kritchevisky,  1988)  found  naturally  and  abundantly  in  all  plant foods. It is defined as ‘polysaccharides and lignin that are not digested in the human small intestine’ (Champ, Langkilde, Brouns, Kettlitz & Collet, 2003). In cereals, starchy roots and tubers, it occurs as water-insoluble NSP (cellulose and lignins). The more water-soluble NSP tend to have viscosifying properties and occurs in leguminous seed crops mostly as storage polysaccharides (gums and hemicellulose); and in leaves, vegetables and fruits as pectin. The benefits of dietary fibres in relation to chronic diseases have been reported by some workers (Fung, Glen,  John-Cliff & Feritt, 2002; Jenkins  et al., 2003; Champ et al., 2003; WHO,

2003). Specifically, there have been reviews on the role of soluble dietary fibre-rich foods in the dietary management of diabetes and cardiovascular diseases (Odenigbo, 2001; McCarty,

2004). Despite these findings, there are stray reports on the beneficial effects of dietary fibre- rich traditional diets based on the more commonly and highly cherished starchy staples.

More recently, resistant starch has received attention as one of the components  of carbohydrate foods that is closely linked to glycaemic control. This is because the  dietary fibre analytical methods were unable to recover oligosaccharides and carbohydrate polymers of less than 50 or 60 degrees of polymerisation (DP) (Champ et al., 2003). Resistant starch has been defined as starch that escapes digestion in the small intestine and becomes available for fermentation by the microflora in the large intestine  (Englyst and Cummings, 1990). It has been shown to have a close link with gelatinization, a process that leads to the production of retrograded starch. Evidently,  gelatinization favours starch hydrolysis and production of high  glycaemic  index  foods.  Conversely,  retrogradation  retards  digestion  and  attenuates blood glucose response to  foods. Due to its health implications,  it has been recommended that food labels should reflect the resistant starch contents of foods. Currently, it appears that such information on local foods is not existent in Nigeria.

The various sources of dietary fibre and resistant starch contain different levels  of active  ingredients  (Imeson,  1994)  with  varying  glycaemic  effects  (Onyechi  et al.,  1998; Champ et al., 2003). This variation is associated with the term glyacaemic index (GI). Leeds, Brand-Miller, Foster and Colagiuri (1998) described it as the ranking of foods based on their immediate effects on blood glucose levels compared with equal amount of reference food (a substance which produces the greatest rise in blood sugar  levels). The starchy foods have high  GI  (>70%)  and  are  consumed  as  main  ingredients  in  mixed  meals  traditionally

compared  to  the  low  values  (<50%)  for  legumes,  fruits  and  vegetables.  The  latter  are consumed  in lesser  quantities  in Nigeria.  The low-GI  foods have different  effects  when utilised in isolation and in mixed diets. Considering high intake of carbohydrate in Nigeria, what  would  people  with  diabetes  in  Nigerian  reckon  with?  The  quantity  or  type  of carbohydrate consumed? Both have been shown to play  important  and respective roles in determining the physiological effects of dietary fibre in diabetes control (Ellis, 1999).This calls for evidence-based  studies that might  highlight possible ways of developing low GI starchy  staple-based  traditional  diets/products  and  a  sound  dietary  guideline  for  type  2 diabetics in Nigeria.

It  has  been  argued  that  high  dietary  fibre  intake  influences  mineral  and  vitamin bioavailability. This presents a risk of deficiencies of these nutrients, especially with regard to those associated with diabetes control like zinc, iron, calcium and magnesium as well as thiamin, riboflavin and niacin. Many foods rich in fibre have also been reported to be rich sources  of  nutrients  such  that  mineral  uptake  and  thus  mineral  balance  would  not  be adversely influenced by ingestion of these foods (Frolich, 1996). It appears then that there exists an agreement among proponents of dietary fibre research that the risk of mineral and vitamin deficiencies is minimal when dietary fibre intake is reasonable and the mineral and vitamins  intake  adequate.  The  need  to elucidate  information  on amount of minerals  and vitamins provided by a high-fibre traditional diet as well as the amount absorbed and used by the body becomes imperative.

The International Institute of Tropical Agriculture (IITA, 1988) has defined a staple food  crop  as  that  which  accounts  for  more  than  200  calories  per  day  in  the  diet  of individual.Tubers/roots contain 1-1.4% protein, 24.5-35% carbohydrate (Platt, 1985) and 8.5- 17.4% dietary fibre (Tanya, Mbofung & Keshinro, 1997). The proteins of roots and tubers are  deficient  in  sulphur-containing  amino  acids  (methionine  and  cystine)  (Bradbury& Halloway, 1988).Cereals contain 6.96-13.69% protein, 68-89.89% carbohydrate (Osagie & Eka, 1998) and 5.1-6.4% dietary fibre (Tanya et al., 1997). The nutritional quality of most cereals is poor because they contain less of the  essential  amino acids, particularly lysine, needed for growth and maintenance (FAO/WHO, 1973). Both roots/tubers and cereals are generally  less  viscous.  The  more viscous  legumes  (including  oil seeds)  contain  20-40% protein, 41-61% carbohydrate but 18-20% for oils seeds (Platt, 1985; Osagie & Eka, 1998), and 6-25% dietary fibre (Ene-Obong & Carnovale, 1992; Nwokolo & Smartt, 1996). Any food  processing  technique  that  would  improve  the  nutritional  quality,  physico-chemical

properties and glycaemic  indices of these important edible traditional staples would  affect better glycaemic control.

Fermentation   was   identified   as   simple   economic   household   and    industrial biotechnological technique. However, household fermentation is more widely used in Nigeria and  has  wide  application  traditionally  in  many  parts  of  the  world  (Alnwick,  Moses  & Schmidt, 1987). Although very few fermented foods are produced and consumed in Nigeria, they make appreciable contribution to the nutrient intake of Nigerians (Onofiok, Nnanyelugo & Ukwondi, 1996). A lot of work has been conducted on the effect of fermentation on plant foods  to  improve  their  nutritional  quality  (Obizoba  & Egbuna,  1992;  Nzomiwu, 1994); bioavailability (Nnam, 2008) safety (Mortarjemi & Nout, 1996) and acceptability (Tomkins et al., 1987).  Available  information  on the effect  of  fermentation  on carbohydrates  only reported increases in total soluble and reducing sugars (Oyewole & Odunfa, 1989; Mlingi,

1987) and reduced starch, oligosaccharides and total crude fibre levels (Riet, Weight, Cilliers & Datel, 1987). Such works aimed at reducing the dietary bulk properties and viscosity of foods to improve starch and protein digestibility and nutrient density of the diets for feeding infants and young children to treat and /or control malnutrition.

Natural fermentation is recognized as an important processing method of cassava and corn (maize) into food for household consumption (Odunfa, 1985). Ihedioha and  Chineme (1999) had reported that depletion of protein of “gari”, which was associated with increased fermentation  period  (72-96h),  led  to  increased  diabetogenicity  in  rats.  On  the  contrary, controlled  fermentation has been used for protein enrichment of  cassava and maize flours (Azoulay et al., 1980) used fermentation  methods  for  protein enrichment  of cassava and maize flours with Candida tropicalis. Their results showed increases from 3.1-18.8%, 1.1-

7.7%,   0.7-2.7%,   0.5-2%   for   total  protein,   lysine,   methionine   and   cystine   contents, respectively.  From  the  above  literature  and  considering  the  factors  that  affect  GI  of  a food/diet  already mentioned  earlier, it is pertinent  to employ a  fermentation  process that would both improve the protein level and modify the  carbohydrate contents of the starchy foods/diets. This process should maintain an acceptable level of digestible carbohydrate of the starchy staples as well as favour an increase in their GI lowering properties.

The burden of chronic diseases is rapidly increasing worldwide. These diseases are defined  by World  health  Organization  (WHO)  (2009)  as  diseases  of long  duration  and generally slow in progression. They include, cardiovascular diseases (including hypertension and stroke), respiratory diseases, diabetes, obesity, some cancers and liver cirrhosis (WHO, 1990). There is mounting evidence that these diseases are the major cause of preventable

deaths in adults in both the richest and the poorest countries (WHO, 2006). In 2001, these diseases contributed approximately 60% of 56.5 million total reported deaths in the world and approximately 46% of the global burden of disease (WHO, 2003). It has been projected that by 2020, diet-related non-communicable chronic diseases (NCDs) will account for three- quarters  of  all deaths  worldwide  and  that  70%  of deaths  due  to diabetes  will  occur  in developing countries. A worrying trend in Nigeria is that priority is given to alleviation and eradication  of hunger,  malnutrition  and infection  while little concern has been shown to combat diet-related NCDs in the country.

Diabetes is no longer regarded as the disease of affluent countries. In 1998,  WHO declared it a major public health problem, which cuts across all races of the world. It ranks fourth among the diseases  of public  health importance  worldwide  (WHO,  2006). It is a disorder characterized by an elevation of fasting blood glucose, caused by relative or absolute insulin deficiency (WHO, 2006). It is mainly associated with disturbances of carbohydrate metabolism.  It also  involves  disturbances  of fat  and  protein  metabolism.  It subjects  the sufferer to a variety of difficulties and presents a high level of complications, which if not properly managed, can lead to death. There are two major types of diabetes: type 1 and type

2 diabetes  mellitus.  They are also  known  as insulin  dependent  (IDDM)  and  non-insulin

dependent diabetes (NIDDM). Type 2 diabetes, is the most common type, accounting for 90-

95% of all diabetes cases (Levitt, 2008). About 10% of the national income of most countries in Sub-Saahara  Africa  is spent  on diabetes  treatment  (Mbanya  & Ramaiya,  2006).  The enormous and escalating economic and social cost of type 2 diabetes,  make  a compelling case for attempts to reduce the risk of developing the condition  as  well as for energetic management of this established disease.

Diet  is  recognized   as  an  important  component   in  diabetes  management.   The beneficial effects of dietary fibre content of plant foods in moderation of glucose and lipid metabolism, mostly due to their viscous and fermentability properties have been reviewed above.  Actualization  of  these  health  benefits  has  remained  a  mirage  in Nigeria  due  to disproportionate intake of high GI starchy staples even in combination with dietary fibre-rich food sources like legumes. Inadequate habitual intake of fruits and vegetables at household level poses additional problem to achieving good glycaemic control. Growth of interest in the modification of starch contents of plant foods with high GI, to clinically safe levels, has been put forward as one of the strategies to encourage inclusion of more plant foods in the diets. It is necessary to explore food processing techniques that could help to achieve such objectives. It becomes imperative to study the  nutritional and therapeutic potentials of the processed

traditional starchy staples and selected under-exploited indigenous leguminous plant foods as well as their metabolic effects when consumed as mixed diets.

1.2      Statement of the problem problem

Nutritional problem of public health importance is one that affects over 1% of the population. Type 2 diabetes mellitus qualifies as one and its prevalence rate appears to be on the increase. According to ACC/SCN report (1997), diabetes mellitus ranked fifth among the leading NCDs worldwide, affecting about 2% and 2.2% of the world’s population. A decade later,  diabetes  escalated  from  fifth  to  fourth  position  among  the  NCDs  (cardiovascular diseases, cancers, chronic respiratory diseases and diabetes)  with prevalence rates of 30%,

13%, 7% and 2%, respectively WHO (2006; 2008). A similar number remain undiagnosed (Parillo & Riccardi, 2004). WHO (2001) projected a 122% rise in the number of adults with diabetes  by  2025.  It  thus  appears  that  more  people  are  continuously  affected  due  to population growth without a corresponding increase in prevalence rate.

The overall prevalence  of type 2 diabetesin  Africa  is 4.5% (Mbanya  &  Ramaiya,

2006). In rural Africa, it is less than 1%. However, it escalates up to 30% in the urban areas as a consequence of unhealthy lifestyles. These include abandonment of natural foods which are rich in complex carbohydrates, proteins and dietary fibres for high consumption of high fat  and  highly  processed  and  genetically  modified  and  refined/sugary  foods,  sedentary occupations, inadequate physical activity, stress, tobacco use and increased drug and alcohol consumption. Jervell (1995) stated that diabetes is not only a chronic disease but also a risk factor  for  coronary  heart  disease,  hypertension,  stroke,  myocardial  infarction  and  even sudden death, accounting for 9% of all deaths (WHO, 1999).Diabetes is the only metabolic disease that has direct  influence on the three major energy–giving nutrients (CHO, fat and protein).  Uncontrolled  type 2 diabetes  precipitates  risk of developing  complications  with increased  morbidity and mortality rates. Its attendant  high cost of medical  treatments,  is reduced if good glycaemic control is maintained.

In Nigeria,  a national  survey  recorded  an average  prevalence  rate  of  2.7%  with similar pattern in both sexes and slightly varying prevalence rates in different geographical locations   (FMH,  1992).  The  International   Diabetes   Federation  (IDF)   (2003)recorded

3.9%.One-third of Nigerians live in urban areas with growth rate of 6% per year (ACC/SCN,

1993) and annual increase of 0.3% in prevalence  rate of type II diabetes. Again, a  good number  of  people  still  live  with  it  undiagnosed.  Based  on  this,  the   prediction  that undiagnosed  diabetes  would  have  approached  25% by 2010  is  worrisome,  especially  in

southern Nigeria where densely populated urban centres predominate.  With the  prevailing trend  of replacing  the consumption  of more complex form of traditional  diets with high intake  of  refined  carbohydrates  (Western)  diets,  the  situation  in  Nigeria  calls  for  great concern and urgent action because carbohydrate (CHO) food  group forms over 70% of the local diets.

One major predicament in achieving good glycaemic control in Nigerian diabetics is

lack of evidence-based  dietary guidelines developed from locally available and  commonly consumed  foods/dishes  that would integrate  individuals’  food habits with  their lifestyles. Over  the  years,  diet  has  been  implicated  both  as one  of the  aetiological  factors  to  the development of diabetes (Hoet, 1997) as well as a key component in diabetes management (Pan, Li & Hu, 1997). Despite this level of scientific knowledge, progress in production and evaluation of most appropriate diets for  diabetics  has been slow and complicated.  This is because the plant foods which form the base for the diets are under-exploited.

Food  habits  are  very  difficult  to  change.High  intakes  of  carbohydrate-rich  food sources in Nigeria,  particularly cereals,  roots/tubers,  have qualified  them as  staple foods. Restriction of carbohydrate–rich sources is a serious threat to Nigeria’s survival. Diabetics are  particularly  adversely  affected  due  to  misinformation  and  inability  to  seek  dietetic intervention.  Such  dietary  misinformation  has  led  to  the  development  of  psychosocial problems in diabetics because they feel denied and full of anxiety in anticipation of lifestyle changes  (Nicholas,  1996).  Nigeria  is  also  endowed  with  numerous  leguminous  plants. Therapeutic potential of some of these legumes have been documented (Onyechi et al., 1998; Odenigbo, 2001). Many of the leguminous seeds used for thickening soups, sauces and stews in Nigeria have been documented  (Udenta, Ellis & Thomas, 2004); and are often eaten as accompaniments with the “foo-foo” prepared from starchy staples.

Conventionally,   type   2   diabetes   is   controlled   with   diet   alone   or   diet   and hypoglycaemic  drugs (in combination with insulin in few cases). Most often,  diabetics are advised to consume only those foods with low GI values like legumes, vegetables and unripe plantain. The restriction has two adverse effects: either the diabetics become too rigid with their  food  selection  which  might  cause  starvation  and  frequent  hypoglycaemic  attacks (Macdonald, 1998) or consume more  carbohydrate per meal from the low GI diets, which precipitates poor diabetic control (hyperglycaemia) (Sameron, Manson, Stampler, Colditz & Willet, 1997). This has resulted in reduced intake or total avoidance of starchy staples and overall  poor  diabetes  management  in  Nigeria  with  its  attendant  high  cost  of  medical treatment. Considering the high intake of starchy foods in Nigeria, it is imperative to explore

possible ways of ensuring adequate and safe levels of intake of indigenous rich sources of carbohydrate to achieve good glycaemic control for people with diabetes. Nutritionists and Dietitians,  in addition to their  role of ascertaining  the nutritional  quality,  bioavailability, safety and acceptability of the biotechnologically produced plant foods are also challenged to explore    their    therapeutic    potentials    through    simple    biotechnological    techniques. Unfortunately,    the   commonly   employed    simple    and    more   economical    household fermentation techniqueapplied during the traditional methods of processing and preparation of the starchy staplesreduces viscosity and highly degrades the starch content of the foods, producing high GI foods that increase post-pandrial blood glucose. Exploring a fermentation technique  that  uses  a  particular  organism  under  controlled  conditions  to  improve  the nutritional quality and GI of the starch-based traditional diets deserves much more attention. This calls for  an alternative fermentation process like controlled  fermentation,  though this technique may be difficult for household level application.

The  drift  from  rural  to  urban  areas  continues  to  be  on  the  increase  with   a corresponding rise in the prevalence of type 2 diabetes resulting from high consumption of refined carbohydrate or carbohydrate overload from dietary intake.   There is need to match the challenging trend in dietary habits biotechnologically using locally available plant foods that are beneficial to health when packaged for consumption in bothrural and urban areas.

Dietary fibre and resistant starch have both been recognized as the major interrelating factors  that  determine  the  bioavailability  of  carbohydrates  expressed  as  GI  (Englyst  & Englyst, 2005). These authors have suggested that food processing techniques that retain or introduce  characteristics  that  slow  carbohydrate  digestion  should  be  explored.  Mitchell, Greenfield and Doelle (1986) developed a model for protein enrichment of starchy foods for developing   countries   using   semi-solid   state   controlled   fermentation,   which   involves gelatinization and production of retrograded starch (mainly amylose) from processed cereals. Use of microorganism  like C.  tropicalis (Azoulay et al., 1980) and Rhizopus oligospurus (Mitchell  et  al., 1986)  in  controlled  fermentation  have  improved  the  protein  content  of cassava and corn  flours.  There is dearth of information on the effect of this fermentation technique on  the nutrient and non-nutrient  composition  of fermented  staple food crops in relation to glycaemic index (in vitro).

Harden, Judd and Hockaday (1993) advocated direct evaluation of GI of many meal combinations based on indigenous, more widely and frequently consumed foods. From the point  of  view  of  improving  the  glycaemic  control  and  lipid  metabolism,  two  principal

approaches  have  been used  to  study the effects  of increasing  carbohydrate  and  fibre  in diabetes management:

i) by supplementation of the low fibre foods with fibre-rich sources (for instance, guar gum, flours from tallow tree and counter wood tree seeds and locust bean); and

ii) by selective use of dietary fibre–rich foods.

The supplementation of foods with water-soluble NSP has been more successful clinically (Onyechi et al., 1998) without much consideration to the fibre supplied by other ingredients in  the  recipe  used.    According  to  Lupien  (1998),  purified  forms  of  fibres  ingested  as supplement are more likely to compromise mineral status because they do not contribute to mineral uptake and would provide some free groupswith an affinity for binding minerals. The controversies among the proponents of dietary fibre research regarding the effects of dietary fibre-rich foods on mineral bioavailability (Faireahter-Tait  & Hurrell, 1996, Gibson, 2007) further stresses the need to explore  fully the effects and nutritional benefits of traditional diets by selective use of dietary fibre–rich indigenous foods.

Therefore, the second approach of selective and holistic use of dietary fibre content of a mixed meal than the soluble-NSP supplements needs to be explored. However, one major limitation of this option is lack of information on dietary formulation using a  food-based approach (FAO/WHO, 1996), which portrays long term effects of diets as consumed. There is dearth of information on the total dietary fibre content and the ratio of soluble to insoluble dietary fibre fractions of low GI meals as consumed traditionally in Nigeria as well as their clinical effectiveness.

The thrust of this research is to explore food processing techniques that would reduce the GI of the more commonly consumed starchy staples used as “foofoo” and use selective approach with food-based dietary guidelines to formulate dietary fibre-rich blends fromthe processed   starchy   staples   and   selected   under-exploited   leguminous   soup   thickeners; andinvestigate their nutrient profile as well aseffect of such traditional foods on glycaemic response in diabetic adult rats.

1.3      General objective

The study investigated the effect of controlled fermentation of some traditional foods on the glycaemic response of diabetic adult rats

Specific objectives were to:

1.   isolate and use Candida tropicalis in controlled fermentation of the cassava, maize and sorghum flours;

2.   determine  proximate  composition,  dietary  fibre,  starch,  viscosity,  in  vitro  GI  and micronutrients  of the fermented  starchy and unfermented  legume  flours  from  Cola gigeantea and Bielschmeidia gabonensis);

3.   determine anti-nutrients and food toxicants in the legume flours;

4.   select fermented starchy staples as well as the legume with desirable physicochemical profile for diet formulations;

5.   determine the chemical content of the these diets and

6.   evaluate the effects of these diets on blood glucose, protein utilization, mineral and vitamin bioavailability in diabetes–induced adult rats.

1.4      Significance of the study

There  are  discrepancies  between  the  dietary  recommendations  for  people  with diabetes  and the actual practice by diabetics  due to differing  food  habits and  inadequate dietetic information. This has posed some challenges on researches. The findings from this research, if adequately published, may provide baseline data that willgive rise to evidence- based practice for the control of diabetes in this part of the world or rekindled the interests of food and nutrition-related scientists for further research on the traditional food crops studied.

The evidence from the results could be used by local food industries. These industries could in turn produce the controlled-fermented  dietary fibre-rich,low  GI  starchy flours at affordable prices for culinary use in both rural and urban household.

The in vitro method of estimating the glycaemic indices of foods appears to be a more cost-effective  method  than  in  vivo,  especially  if human  subjects  are  involved.  The  data obtained  on  GI  values  of  locally  available  foods  through  this  method,  could  be  used subsequently to generate data for compilation of GI values of our local foods. The additional data generated from the chemical analyses of traditional foods studied could also be used to complement the information in the Food Composition Tables currently being used. These information will be useful to Dietitians, Nutritionists and other food related scientists.

Most often, people with diabetes over-restrict their intake of starchy staples. It is believed that the results of this study may provide scientific evidence for dietary management of type

2 diabetes mellitus. It would assist to improve the quality of information disseminated to the diabetic population, their families and entire community by dietetic and other  health-care professionals, especially those involved in diabetes care. Over time, this may contribute to the continuous search for effective ways of possibly reducing morbidity and mortality rates as well as complications associated with uncontrolled type 2 diabetes mellitus.

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