Food Science and Technology Project Topics

Proximate and Consumer Acceptability of Biscuit Produced From Wheat (Triticum Aestivum L), Soursop (Annona Muricata) and Soybean (Glycine Max) Blends

Proximate and Consumer Acceptability of Biscuit Produced From Wheat (Triticum Aestivum L), Soursop (Annona Muricata) and Soybean (Glycine Max) Blends

Proximate and Consumer Acceptability of Biscuit Produced From Wheat (Triticum Aestivum L), Soursop (Annona Muricata) and Soybean (Glycine Max) Blends

Chapter One

Aims and Objectives of the Study

            The aim of this study is to produce biscuits from composite flour, to determine the proximate composition and consumer acceptability of biscuits produced from wheat, sour sop and soy flour blends



 Soursop (Annona muricata L)

            Annona is a genus of tropical fruit trees belonging to the family Annonaceae, of which there are approximately 119 species. Seven species and one hybrid are grown for domestic/ commercial use. Annona muricata L. is known as soursop in English-speaking countries and is referred to by numerous common names (Bueso, 2000). After the arrival of the Spanish in the Americas, the Annona species were distributed throughout the tropics (Popenoe, 2000). Soursop trees are widespread in the tropics and frost-free subtropics of the world (Morton, 2003) and are found in the West Indies, North and South America, lowlands of Africa, Pacific islands, and Southeast Asia. The soursop fruit and other parts of the tree are considered to be underutilized. Information on the composition, nutritional value, medicinal uses, and toxicology of the soursop fruit and plant is limited and scattered (Morton, 2003).

Botany and Horticuture

The soursop is an upright, low-branching tree reaching 8 to 10 meters (Popenoe, 2000). The tree has green, glossy evergreen leaves. The flowers appear anywhere on the trunk or any branch. It is usually grown from seeds which can be stored for several months before planting. Germination of seeds usually takes 3 weeks, but under suboptimal conditions can be delayed for up to 2–3 months. Alternatively, propagation of the Annona species is achieved by cuttings for rapid multiplication of new genotypes and for the elimination of viral and disease infection. With the exception of a few cultivars, clonal propagation of the Annona species by cutting orair layering has not been very successful (Rasai et al., 1995). Vegetative propagation of rootstocks or cultivars of known agronomic potential could eliminate tree to tree variability in growth and productivity (George and Nissen, 2007). However, the seedling rootstocks are highly variable in vigor and disease resistance and consequently scion growth and productivity are also variable. They are considered as minor tropical fruits due to strict environmental requirements for tree planting and the short post-harvest life of their fruits (Encina, 2005).

Fruit Description

The soursop tree produces dark green, spiny aggregate fruits made up of berries fused together with associated flower parts (Thompson, 2003). The oval or heart-shaped and frequently irregular lopsided composite soursop fruit is derived from the fusion of many fruitlets and can weigh more than 4 kg (Coronel, 2003). The fruit pulp consists of white fibrous juicy segments surrounding an elongated receptacle (Paull, 1998). In each fertile segment there is a single oval, smooth hard, black seed {1/2}–{3/4} in (1.25–2 cm) long (Morton, 2007). A fruit may contain as few as 5 or up to 200 or more seeds (Paull, 1998). The reticulated leathery looking skin has short spines (Paull, 1998). Its inner surface is cream colored and granular and separates easily from the mass of white, fibrous juicy segments which surround the central soft pithy core (Morton, 2007). In Puerto Rico, the seedling soursops are roughly divided into three general classifications: sweet, sub-acid, and acid. These are subdivided as round, heart-shaped, oblong, or angular and finally classed according to flesh consistency which varies from soft and juicy to firm and comparatively dry (Morton, 2007).

Compositional Characteristics of Soursop Fruit

The soursop fruit consists of 67.5% edible pulp, 20% peel, 8.5% seeds, and 4% core by weight (Sanchez-Nieva et al., 2003). The white edible pulp contains 80–81% water, 1% protein, 18% carbohydrate, 3.43% titratable acidity, 24.5% non-reducing sugar, and vitamins B1, B2, and C (Onimawo, 2002; Morton, 2007). Some physicochemical characteristics were refractive indices of 1.335 for the seeds and 1.356 for the pulp, pH values of 8.34 for the soursop seed and 4.56 for the pulp, and soluble solids contents of 1.51Brix for the soursop seed and 151Brix for the pulp (Onimawo, 2002).

The second most abundant component of soursop pulp next to water is the sugars, which constitute about 67.2–69.9% of the total solids (Sanchez-Nieva et al., 2000). The reducing sugars, glucose and fructose, were 81.9–93.6% of the total sugar content. Using gas–liquid chromatography (GLC), fructose, D-glucose, and sucrose contents of soursop pulp were 1.80, 2.27, and 6.57%, respectively, to make a total sugar content of 10.48% (Chan and Lee, 2005).The soursop fruit contains 12% sugar (mostly glucose and some fructose), pectin, potassium, sodium, calcium chloride, and citrate (WHO, 2001). Table 39.4 shows that the citrate concentration in soursop juice was higher (8.82 g/L) than in WHO/UNICEF Oral Rehydration Salt (ORS) preparation standard (2.9 g/L) in the form of trisodium citrate dehydrate (Enweani et al., 2004).

The fiber content of soursop pulp was reported as 0.78 and 0.95% (Wenkam and Miller, 2005). The alcohol-insoluble solids were mainly pectin, which in ripe fruit is 0.91% on a fresh weight basis. The fraction declines from 12.0 to 4.0% on a dry weight basis from preclimacteric to climacteric stages (Paull, 2002).

The wet weight of soursop pulp has been reported to be 0.055 gN/100 g (Ventura and Hollanda-Lima, 2001). Ninety-one percent of this amount was contributed by the acid and neutral free amino acids. Eleven free amino acids were identified by paper chromatography and four other unidentified ninhydrin-positive components were detected. Proline and γ-aminobutyric acid were the most abundant free amino acids. Other amino acids detected, in order of relative amount, were glutamic acid, aspartic acid, serine glycine, alanine, citrulline, cysteine (or cystine), arginine, and lysine (Paull, 1998).

A study of the pre-harvest deterioration of soursop and its effect on nutrient composition was conducted in Ibadan, southwestern Nigeria (Amusa et al., 2003). Four fungal pathogens including Botryodiplodia theobromae, Fusarium sp., Rhizopus stolonifer, and Aspergillus niger were found to be associated with the pre-harvest deteriorating soursop. Nutrient analysis revealed that the freshly harvested non-infected soursop fruits had 78.49–78.68% moisture content, 14.88–14.91% carbohydrates, 1.20–1.24% crude protein, 0.89–0.90% ash, 19.15–19.35% dry matter, 1.39–1.41% potassium, and 0.63–0.65% sodium at five tested locations. Comparable values have also been documented by Rice and colleagues (Rice et al., 2001). An approximate 39% reduction in the carbohydrate contents was observed in the infected freshly harvested fruits (Amusa et al., 2003). This was probably due to the degradative activities of the pathogens leading to reduction of the quality of the fruit. The infected fruits had about 20 and 11% loss in crude protein and dry matter, respectively. However, the ash and moisture contents of the infected fruits were higher than those of the non-infected ones.





Soursop (Annonamuricata), Wheat (Triticumspp) and Soybean (Glycine max) used in this research work were purchased from a local market in Owo, Ondo State. The Soursop, Wheat and Soybean were purchased wholesome, that is, it was free from rot and had no physical damage. The milk powder, sugar, egg, salt, margarine, baking powder and flavor were also purchased from the same local market in Owo, Ondo state. The biscuit produced from Soursop, Wheat and Soybean was processed in the processing laboratory of Food Science and Technology. Equipment, chemicals (reagents) and other facilities used in the research work were obtained from the laboratories of the Department of Food Science and Technology, Rufus Giwa Polytechnic Owo, Ondo State.


Production of soursop flour

Soursop fruits were processed into flour as shown in Figure 1. Matured and ripped soursop fruits (3 kg) were washed under running water and peeled gently with stainless knife. The peeled fruits were sliced into 5 mm thickness and the core and seeds removed, then the pulp was cut into small pieces and oven dried at 60ºC for 48 hrs. The dried fruit was milled into flour using a Nutri-Blender and was passed through a US70 (180µm diameter) sieve. The flour obtained was stored in an air tight plastic container at room temperature (37oC) to prevent spoilage of sample until used for further analysis.




Table 4.1: Proximate composition of biscuits produced from wheat, soursop and soybean





Based on the research, the blends of wheat, soursop and soybean flour of highly nutritious and acceptable by the consumer. Biscuits of acceptable sensory and chemical quality have been produced from wheat, soursop and soybean composite flour thereby suggesting an improvement for the nutritional content of biscuits which is a widely consumed snack. The research was found to explore the use of soursop and soybean. The closeness of values obtained for all biscuits samples to the control sample indicate a high level of acceptance of the wheat, soursop and soybean biscuits. Hence, suggesting a nutritious value to diets.


Biscuit is a convectional snack produced from wheat flour with other ingredients: sugar, baking powder, margarine e.t.c. just like any other cereal based foods, it is high in carbohydrates but low protein therefore, improving the protein content of such of such highly consumed snack cannot be over emphasized. The incorporation of protein based food such as soybean will increase the protein content of biscuits and also improve the nutritional value of such products.


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