Chemical analysis to promote the use of wild fruits from Mozambique

Abstract

Abstract

Wild fruit trees have significant cultural and socio-economic value in rural areas of Mozambique. Most of the wild fruits are seasonal and are available mainly in the wet season. Generally they have a short shelf-life and are eaten fresh or after minimal processing; the most common method of preservation is sun-drying. The fruits of Adansonia digitata, Landolphia kirkii, Salacia kraussii, Sclerocarya birrea, and Vangueria infausta were selected for this study.

New data on nutritional components and other characteristics have been obtained. The pH, titratable acidity and the content of soluble solids in the fruit pulps were determined. The organic acids citric, malic and succinic acids were

found at various amounts in all pulps. The contents of different mono- and disaccharides were also analysed in the pulps.

The protein content was low in all the fruit pulps, as is the case in fruits in general. However, the protein content was h igh in the k ernels o f A. digitata and S. birrea, about 30 to 40% on d ry matter b asis. The total content and relative amounts of the different essential amino acids are with a few exceptions similar to or above that recommended by the WHO for children aged 3 to10 years. The fat content was below 2% in the fruit pulps, while the fat content in A. digitata kernels was almost 40%, and S. birrea kernels about 60%. The kernels of A. digitata and S. birrea are rich in unsaturated fatty acids, and constituted about 68 and 80%, respectively, of the total fat. The A. digitata kernels contained appreciable amounts of essential fatty acids; the amount of linoleic was about 30% and linolenic acid 2%. S. birrea kernels contained about 7% linoleic acid.

The fruits contained both insoluble and soluble dietary fibre. The pulp of A. digitata had the highest amount of soluble dietary fibre, around 60% (on dry matter basis), while V. infausta pulp had the highest amount of insoluble dietary fibre, around 40%. The kernels contained 3 to 5% phytic acid which may decrease the absorption of minerals.

Treatment with phytase reduced the phytic acid content by 20 to 30% after only 15 minutes enzymatic incubation. Interestingly, a lmost 50% o f the e stimated o riginal content of minerals was found in the supernatant after a few minutes enzyme incubation. The amount of iron in the pulps ranged from 1 to 9 mg/100 g (on dry matter basis); the highest amount being observed in S. kraussii. The highest iron content, 29 g/100 g DM, was found in whole seeds of A. digitata, 29 mg iron/100 g. The A. digitata pulp contained an appreciable amount of calcium, and the kernel also

had high content of calcium. In conclusion, data from this study can be used to encourage the increased consumption of these wild fruits and kernels. In addition, the results of the analysis of the investigated fruits can form the basis for the selection of fruits for wider use, domestication, and processing to extend their shelf-life and for the manufacture of other food products.

Abstract (Swedish)

Popular Abstract in English

Wild fruits trees species are widely distributed throughout the African countries.

Many of these trees species produce fruits, which are used by the local communities

to greater or less degrees. The importance of wild fruits in the diet depends to a large

extent on the availability of the fruits, since cultivated fruit trees are not particularly

common in the dry regions of the countries. The goals of this work were to perform a

study on traditional utilization of wild fruits in Mozambique and to generate data on

the composition and other characteristics of five wild fruits as a basis for the selection

of fruits suitable for processing and increased utilisation and consumption of

indigenous fruits.

Fruits of Adansonia digitata (n´buvu), Landolphia kirkii (vungwa), Salacia kraussii

(psincha), Sclerocarya birrea (canhi), and Vangueria infausta (pfilwa), were selected for

this research. When the wild fruits were collected in the different districts, local

people were interviewed about the traditional use of the fruits. The fruits are eaten

raw, pressed to juice, fermented to alcohol beverages, cooked, or used as flour to make

porridge. The seeds and kernels are often used in times of drought when the

production of peanuts is low; the seeds can be ground roasted to make a kind of

coffee, and the kernels of A. digitata and S. birrea may also be roasted to be eaten as

snacks or ground in a bowl, mixed with water, boiled and consumed with local plant

food. In general most people know that fruits are associated with potential health

benefits. Researchers has shown that a wide range of wild fruits have the potential to

provide rural households with free foods to meet their nutritional and medicinal

needs. The disadvantages of the selected fruits are that they grow and ripen during a

very short period of the year and that normally their shelf-life is short.

Different analytical methods were used to evaluate the nutritional components

and other characteristics of some wild fruits. For the fruit processing industry, data on

sugar content, pH and moisture are essential characteristics. They play an important

part in the perception of fruit quality indicating the possibility for future use of these

wild fruits. The sugar content is important for the development of the aroma and

taste, and in product development it is important to find a good balance between for

example pH and sugars to receive an optimal taste. The highest total sugar content

was found in A. digitata and L. kirkii, more than 10g/100 g. Organic acids such as

citric and malic acid influence flavor and aroma and are responsible for many

characteristic fruity tastes; they were found in all fruits in this study. The parameters

above have been reported to influence shelf life, stability and microbiologic safety.

Most of the fruit pulps were juicy except of A. digitata, which was very dry; the

moisture content was only around 10%. The fat and protein contents in the pulps

were low, which is common in fruits. The pulps of A. digitata and V. infausta

contained considerable amounts of dietary fibres. The content of the mineral in the

kernels such as calcium, iron and zinc were found in considerable levels and the have

great contribution for many functions on the human body. Consumption for

example of 100 g A. digitata pulp, can provide around 30% of recommended intake

of calcium for pregnant women and children, and 23% of the iron for 4 to 13 years

old children. Consumption of 40 g A. digitata kernels can provide 20 to 25% of the

recommended intake of iron for children and 16 to 20% from S. birrea kernels. In

addition the recommended intake of zinc provided 20 to 44% from A. digitata, and

16 to 36 % from S. birrea kernels for children and pregnant women.

The fat content in A. digitata and S. birrea kernels was high around 40 to 50%.

Interestingly the fatty acid composition in A. digitata can be compared with that in

peanuts, while S. birrea can be compared with olive oil. A. digitata kernels contained

the essential fatty acids linoleic and linolenic acids and S. birrea kernels contained

only the linoleic acids. Consumption of 40 g A. digitata kernels can cover 60 to 90%

of the daily intake of essential fatty acids for those aged 4 to 13 years, and pregnant

women.

Protein is one of the most crucial nutrients to the human body improving varying

aspects of health. The protein content in the kernels of A. digitata and S. birrea was

around 30 to 40%. In addition, the levels of essential amino acids in the kernels were

comparable with the amino acid requirements stated by the World Health

Organization (WHO). For children aged 4 to 8 years, 81 and 66% of the

recommended intake may be covered by the consumption of 40 g A. digitata kernels

and S. birrea kernels, respectively. The contribution to recommended intake for older

children and pregnant women is lower, but it may be possible for these groups to

increase their intake of kernels, especially if they are eaten as a snack.

The results of this study will be vital in efforts to promote use of these wild fruits.

The data can be used for the estimation of dietary intakes, and for education of local

communities with regard to the nutritional benefits of free sources of food in their

environment. The findings indicate that the nutrient contents of the fruits may help

to meet the dietary requirements for children and pregnant women in rural areas. In

addition they may promote the use of wild fruits and their kernels, and can form the

basis for the selection of fruits for further processing, to extend shelf-life and to

manufacture new products. Initiatives should be put in place for the selection and

domestication of wild fruits trees.

• author: Magaia, Telma
• supervisor: Kerstin Skog
• opponent: Professor Gebre-Medhin, Mehari, Uppsala University, Uppsala
• organization: Department of Food Technology, Engineering and Nutrition
• publishing date: 2015
• type: Thesis
• publication status: published
• subject: Food Engineering
• keywords: pulps, kernels, consumption, fat, protein, minerals, dietary fibre
• pages: 140 pages
• defense location: Room K:B, Kemicentrum, Centre of Chemistry and Chemical Engineering, Getingevägen 60, Lund University Faculty of Engineering, LTH.
• defense date: 2015-09-03 10:15:00
• ISBN: 978-91-7422-406-1
• language: English
• LU publication?: yes
• id: 9a4ca818-8665-4f7d-835e-279659fddebe (old id 5470948)
• date added to LUP: 2016-04-04 11:10:07
• date last changed: 2018-11-21 21:03:04