ABSTRACT
The effect of using different plant ash for alkaline blanching on sprouted and unsprouted soymilk (Glycine max) was determined in this study. The main objective was to assess the quality characteristics of soymilk produced from sprouted and unsprouted soybeans using different plant ash for alkaline blanching. Six formulations of SSPI, SSPB, SSPP, USPI, USPB, USPP were prepared using different plant ash. The results of the moisture content increased from (87.76 to 90.67% for all the soymilk samples. In all the samples. protein content in palm inflorescence enhanced the soymilk protein (5.81%) more than plantain peel (5.54%) and palm bunch (5.42%). High fiber was observed in sample unsprouted samples (USPB and USPP), lower fiber content in sample sprouted samples (SPPI, SPPB, SPPP). Fat content of the soymilk samples ranged from 1.18% in sample USPI to 2.38% in sample SSPP. Ash content was high in this study due to high minerals in the plant ash (1.07 to 1.29%,), for Carbohydrate (2.43 to 3.68%), energy value from (37.91 to 55.92 kcal). Vitamin A content increased from (13.32-15.47 mg/100g) while the vitamin B-group decreased (0.7 to 0.9 mg/100g) and vitamin C from 1.57 to 1.92 mg/100g. Magnesium, potassium, calcium and sodium, increased respectively from 59.32 to 75.44 mg/100g, 72.72 to 77.47 mg/100g, 45.55 to 53.92 mg/100g, 15.92 to 18.12 mg/100g, in zinc 0.90 to 1.25 mg/100g. PH, titratable acidity, increased from (6.77 to 6.18), (0.11 to 0.25) increased in viscosity from (8.02 to 8.08 mPa). All the anti-nutrient content decreased respectively from 0.38 – 0.02, for saponin,1.47 – 0.01 for phytate, 1.29 – 0.02 for tannin, visible coagulation time increased on from 4th - to 14th day in sprouted soymilk while it increased from 3rd – 7th day in unsprouted, which shows that soymilk produced from sprouted soybeans last longer than soymilk produced from unsprouted soybeanss . General acceptability increased from 6.50 to 7.40. Sample USPI milk was most acceptable.
Key words: Sprouted, unsprouted, soybean, plant ash, alkaline blanching, soymilk.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of tables vii
List of figures viii
List of plate ix
Abstract x
CHAPTER 1: INTRODUCTION
1.1 Background of study 1
1.2 Statement of problem 3
1.3 Justification 3
1.4 Objectives of study 4
CHAPTER 2: LITERATURE REVIEW
2.1 Overview of milk 5 2.2 Plant milk 6
2.3 Relevance of legumes in food system 7
2.4 Soybean 8
2.4.1 Nutritional value of soybean 9
2.4.2 Health benefits of soybean 10
2.4.3 Antinutrient factors of soybean seeds 11
2.4.4 Processing and food usage of soybean seeds 13
2.4.5 Sprouting of soybean seeds 15
2.4.5.1 Impact of sprouting on soybean seeds 16 2.5 Soymilk and its significance 17
2.6 Alkaline blanching with plant ash 18
CHAPTER 3: MATERIALS AND METHODS
3.1 Sources of raw materials 20
3.2.1 Processing of plant ash 20
3.2.2 Production of soymilk from unsprouted soybean boiled with plant ash 20
3.2.3 Production of soymilk from sprouted soybean boiled with plant ash 21
3.3 .Method of analyses 25
3.4 Proximate analysis 25
3.4.1 Determination of fat content 25
3.4.2 Determination of moisture content 25
3.4.3 Determination of crude protein 26
3.4.4 Determination of ash content 27
3.4.5 Determination of crude fibre 27
3.4.6 Determination of carbohydrate content 28
3.5 Mineral analysis 28
3.5.1 Determination of calcium and magnesium 28
3.5.2 Determination of potassium 29
3.5.3 Determination of zinc 30
3.5.4 Determination of sodium 30
3.6 Determination of sodium 31
3.6.2 Determination of vitamin B1 (thiamin) 32
3.6.3 Determination of vitamin B2 (Riboflavin) 32
3.6.4 Determination of vitamin B3 (Niacin) 33
3.6.5 Determination of vitamin C (Ascorbic acid) 34
3.7 Physicochemical analysis 34
3.7.1 Visible coagulation time (VCT) 34
3.7.2 Determination of pH 35
3.7.3 Determination of titratable acidity 35
3.7.4 Determination of viscosity 35
3.8 Antinutrient analysis 35
3.8.1 Determination of phytates 35
3.8.2 Determination of saponin 36
3.8.3 Determination of tannin 37
3.9 Sensory evaluation 37
3.10 Statistical analysis 38
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Proximate composition of soy milk samples 44
4.2 Vitamin content of the soymilk samples 45
4.3 Mineral content of the soymilk samples 48
4.4: Physicochemical properties of the soymilk samples 52
4.5 Anti-nutrient composition of the soymilk samples 55
4.6 Sensory evaluation of the soymilk samples 58
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 62
5.1Recommendation 62
REFERENCES 63
LIST OF TABLES
Table 4.1 Results of proximate composition of soymilk samples 44
Table 4.2 Result on vitamin content of the soymilk samples (mg/100g) 47
Table 4.3 Result on mineral content of the soymilk samples (mg/100g) 49
Table 4.4 Result on physicochemical properties of the soymilk samples 54
Table 4.5 Result on anti-nutrient composition of the soymilk samples (mg/100g) 57
Table 4.6: Result on sensory evaluation of the soymilk samples 60
LIST OF FIGURES
Figure 1: Flow chart for processing palm bunch, palm inflorescence and plantain peel ash 22
Figure .2 : Flow chart for production of soymilk boiled separately with palm bunch, Palm inflorescence and ripe plantain peel ash 23
Figure 3: Flow chart for production of soymilk boiled with palm bunch, palm inflorescence and ripe plantain peel ashes 24
LIST OF PLATES
Plate 1: Sprouted beans 39
Plate 2: plant ash 39
Plate 3: soymilk samples 61
Plate 4: processing 61
Plate 5: soymilk samples used for VCT 61
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Recent expectations of consumers for more healthy and palatable food choice have driven the dairy industry to expand their knowledge beyond conventional milk products for the production of various plant-based non-conventional beverages with health benefits equating milk with consumption at recommended levels (Grant and Hicks, 2018). Legumes, cereals and oilseeds due to their rich nutritional profile are the major target for the production of milk substitutes and improvising milk quality with specific bioactive components (Paul et al., 2019). The lactose intolerant and/or individuals allergic to cow milk are prime consumers of plant milks, but they are also in great demand by people without health problems (such as vegans and vegetarians) (Bernat et al., 2014) due to their health-promoting and disease-preventing properties (Paul et al., 2019).
Soymilk also known as plant or imitation milk is an aqueous extract of whole soybeans (dehulled or non-dehulled), closely resembling dairy milk in physical appearance and composition (Mazumder and Begum, 2016). Soymilk possess 2.10 to 3.40 % protein, 5.40 to 9.0 mg/100g calcium, 8.10 to 13.60 mg/100g magnesium, 98.60 to 146.90 mg/100g potassium, 18.30 to 26.40 mg/100g phosphorus, 58.80 to 71.60 µg/ml daidzin, 55.70 to 80.60 µg/ml genistin, 1.60 to 9.80 µg/ml daidzein and 0.60 to 9.40 µg/ml genistein (Niyibituronsa et al., 2019). Soy milk is rich in isoflavones which have many health benefits including reduction of cholesterol, prevention of osteoporosis and reduction of risk for certain cancers (Kant and Broadway, 2015). Soymilk is low in energy, thus, it could enhance health benefits in terms of reducing body weight (Kabiru et al., 2012). Soymilk can be used in processing a wide array of food products like cake (Erfanian and Rasti, 2019) and kunu-zaki (Adelekan et al., 2013). Soymilk can be fortified for complementary feeding (Okwunodulu et al., 2015).
Many techniques have been developed for the production of good quality soymilk. Sprouting of legumes like soybean results to increase in bioactive compounds like phyrosterols, enhancement of amino acid and various antioxidants, reduction of anti-nutrients like trypsin inhibitor (Paolo et al., 2019), and flautelence causing oligosaccharides (namely, stachyose and raffinose) (Marton, et al., 2010). Sprouting also enhances the crude protein and carbohydrate content of soybean, decrease presence of anti-nutrients like phytic acid, tannin and protease inhibitor decreases (Pele et al., 2016), thus providing the base to define sprouts as “functional foods” (Paolo et al., 2019). Alkaline blanching refers to brief immersion of crop in hot water containing plant ash. Plant ash contain oxides of potassium, sodium, calcium which yield their corresponding hydroxides upon its dissolution in water (Babayemi et al., 2010; Uzodinma et al., 2014). Alkaline blanching has the tendency to inactivate enzymes, modifies texture, preserves colour and nutritional value of food products (Kapadiya et al., 2018).
Plant ashes commonly used in alkaline blanching possess varying constituents. Dried palm bunch ash contains 364.78 mg/100g calcium, 183.99 mg/100g magnesium, 68.52 mg/100g sodium, 679.94 mg/100g potassium, 7.52 mg/kg iron, 2.76 mg/kg manganese, 16.4 mg/kg zinc and 9.42 mg/kg copper. Dried plantain ash contains 295.16 mg/100g calcium, 196.02 mg/100g magnesium, 62.77 mg/100g sodium, 528.58 mg/100g potassium, 7.14 mg/kg iron, 2.26 mg/kg manganese, 15.26 mg/kg zinc and 7.66 mg/kg copper whereas dried palm inflorescence possesses 347.56 mg/100g calcium, 193.57 mg/100g magnesium, 70.95 mg/100g sodium, 576.37 mg/100g potassium, 6.35 mg/kg iron, 3.16 mg/kg manganese, 14.84 mg/kg zinc and 10.80 mg/kg copper (Okwunodulu et al., 2018b). Plant ash can be utilized in making ‘Ngu’, an emulsion of oil in water (Udeotok, 2012) and for preparing traditional foods such as ighu, ugba, isiewu, nkwobi, abacha, among many others (Udeotok, 2012).
1.2 STATEMENT OF THE PROBLEM
One of the factors that deter people from consuming soybean is due to the presence of antinutrients like tannin. They interfere with processes such as digestion, absorption, utilization of nutrients like minerals and results to health issues like gastrointestinal disorders and even death (Soetan et al., 2014). Aside from this, there is little or no report in literature on soymilk produced from sprouted soybeans using different plant ash for alkaline blanching. Most processed soymilk encountered phase separation upon storage, poor yield and drudges in preparation.
1.3 JUSTIFICATION OF THE STUDY
Processing of soybean to soymilk with alkaline blanching is one way of reducing the presence of compounds that interferes with absorption of nutrients in soybean. This study will reveal the possibility of alkaline blanching method to retain more nutrients and cause more reduction in anti-nutrients, increase yield due to alkaline boiling which tenderizes the bean and increase the milk yield, and also increase the pH thereby delay the phase separation. Findings of this study will be beneficial to soymilk processing industries, researchers and consumers especially lactose intolerant and/or individuals allergic to cow milk.
1.4 OBJECTIVE OF THE STUDY
The main objective of this study was to assess the quality characteristics of soymilk produced from sprouted soybeans using different plant ash for alkaline blanching.
The specific objectives were to:
i. produced soymilk from sprouted and unsprouted soybeans using different plant ash for alkaline blanching
ii. evaluate the proximate composition, mineral, vitamin, physical properties and antinutrient factors of the soymilk
iii. Evaluate the sensory properties of the soymilk.
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