Báo cáo khoa học nông nghiệp " Commercial and High Quality Cultivars of Root and Tuber Crops for Processing Purpose in the Northern and Central Vietnam " MS7 potx

Nguyen Van Tuat Australian Institution Faculty of Agriculture, Food and Natural Resources, University of Sydney Australian Project Team Leader Professor Les Copeland Outputs 3 and 4 M

Ministry of Agriculture & Rural Development

Collaboration for Agriculture & Rural Development

008/07VIE

Commercial and High Quality Cultivars of Root and Tuber Crops for

Processing Purpose in the Northern and Central Vietnam

Vietnamese Institution Food Crops Research Institute, Ministry of

Agriculture and Rural Development

Vietnamese Project Team Leader Assoc Prof Dr Nguyen Van Tuat

Australian Institution Faculty of Agriculture, Food and Natural

Resources, University of Sydney

Australian Project Team Leader Professor Les Copeland

Outputs 3 and 4

MS7: Sweet potato processing

Preparation of animal feed from sweet potato leaves, vines and roots

Extraction of starch from sweet potato

May - 2010

I Introduction

Sweet potato1 (Ipomea batatas, a member of the Convolvulacae family), is grown in over 100

countries, mostly by small holder farmers It has a high yield potential for biomass production, is adapted to a wide range of habitats and soils, and ranks among the world’s top ten food crops on production volume Sweet potato is a versatile crop The roots are eaten as vegetables or are processed for diverse uses including making noodles and snack foods, fermentation into alcoholic beverages, and production of starch The roots are a good source

of edible energy in the form of starch, and also provide a source of dietary fibre from non-starch polysaccharides Sweet potato leaves are rich in vitamins A and C and have relatively high protein content (25–30% of dry matter) compared to other leafy vegetables The carotene and anthocyanin pigments, which are responsible for the yellow, orange, red, or purple flesh colours of the roots, are a source of natural pigments for the food industry The roots, leaves and vines are used for livestock feeding, as fresh or dried material, or after fermentation into silage

Fresh sweet potato roots normally contain between 20 and 50% dry matter, depending on cultivar and developmental stage of the plant at harvest Carbohydrates make up about 90% of dry matter, most of which is starch The sweetness is due to sugars, mainly maltose but also sucrose, glucose and fructose, which can account for between 5 and 30% of the dry matter The other major components are non-starch polysaccharides (0.5-7.5%), protein (1-10%) and lipids (1-2%) The composition of the roots varies depending on cultivar, environment for crop growth, cultivation practices, postharvest storage, and influences nutritional, quality and taste/texture properties

Sweet potato roots deteriorate in processing and nutritional quality within about 2-3 weeks after harvest, with loss of moisture and starch content and increase in sugars Microbial spoilage, particularly in damaged roots, and sprouting are other potential postharvest problems Processing is an important way of preserving the value of the large amount of biomass produced by sweet potato plants that can not be used by farmers in the short time before postharvest deterioration becomes significant

The overall goals of the project are to improve yield and economic return from sweet potato production in Thanh Hoa, Bac Giang and Quang Tri provinces of Vietnam by

- encouraging adoption of improved cultivars and planting materials

- providing farmers with greater options for value adding

- Enhancing skills of scientists, extension officers and farmers

The specific objectives addressed in this section of the project are to demonstrate simple proof-of-concept methods for

i fermenting sweet potato leaves, vines and roots into a silage-type product for animal feeding, and showing how the process may be adopted by small-holder farmers

ii Large scale extraction of starch from sweet potato roots

1

Recommended usage to differentiate sweetpotato from the potato (Solanum tuberosa), which belongs to the 

Solanaceae

Preparation of animal feed from sweet potato leaves, vines and roots

In this section of the project, a simple and efficient method was developed for processing sweet potato vines, leaves and roots into livestock feed The method was demonstrated to local farmers in Bac Giang, Thanh Hoa and Quang Tri provinces

The biological energy of the sweet potato biomass may be conserved, and the consumption time for animal feed prolonged, by microbially fermenting the leaves, vine and roots under anaerobic conditions Anaerobic conditions have to be maintained subsequently during storage to prevent spoilage of the material due to putrefaction As described subsequently, salt and a source of energy (cassava starch, rice bran or corn flour) are added to the sweet potato biomass, as a starter for fermentation to provide the right conditions for rapid growth of the appropriate microorganisms

Research scope

- Produce livestock feed in Bac Giang, Thanh Hoa and Quang Tri

- Demonstrate the benefits to farmers from using the fermented vine-leaves and roots of sweet potatoes

- Solve technical challenges for fermentation processing and usage of the livestock feed

II Aims

The specific aims were to demonstrate technology that could be used to

- preserve sweet potato roots from microbial spoilage and vermin and thereby prolong the shelf life of feed for pigs and cattle

- improve the digestibility and nutritional quality of the feed by stimulating the production

of organic acids such as lactic and acetic acids and amino acids from the biomass

- Improve the organizational efficiency of farms by saving energy and labour in preparing feed for livestock and by processing the large volume of sweet potato biomass in a timely manner after harvest and before the next crop

- Increase economic efficiency of livestock growing by utilising all of the sweet potato biomass, including roots unsuitable for human use because they are too small or large, or damaged

III Methods

3.1 Locations

In Bac Giang province:

- Bich Son ward in Viet Yen town

- Ngoc Chau ward in Tan Yen town

- Mai Trung ward in Hiep Hoa town

In Thanh Hoa province:

- Nguyen Binh ward in Tinh Gia town

- Quang Luu in Quang Xuong town

- Dong Thanh ward in Dong Son town

In Quang Tri province

- Vinh Thai ward in Vinh Linh town

- Gio Hai ward in Gio Linh town

- Hai Quy ward in Hai Lang town

3.2 Ingredients for preparing livestock feed

- Sweet potato leaves, vines and roots, sliced and dried under the sun until tender

- Dried rice bran or corn bran or corn flour

- Salt

3.3 Technology transfer methods

- Train and transfer to farmers the techniques to use vine-leaves and roots of sweet potatoes

- Design experiments to assess the processing by fermentation of the sweet potato biomass

in 15 households in the 3 towns of each province in order to recommend these processes

to other households

- Prepare different ingredients for fermentation processes of the sweet potato biomass:

o For the sweet potato vine and leaves

ƒ 90% wilted vine-leaves + 10% rice bran + 0.5% salt

ƒ 97.5% wilted vine-leaves + 2.5% sugar cane molasses + 0.5% salt

ƒ 94% fresh vine-leaves + 6% corn flour + 0.5% salt

o For the sweet potato roots

ƒ 10% root + 89.5% fresh vine-leaves + 0.5% salt

ƒ 25% root + 75% fresh vine-leaves + 0.5% salt

ƒ 50% root + 50% fresh vine-leaves + 0.5% salt (Note: the starch in the sweet potato roots serves as the energy source and hence sugar, molasses, corn starch, etc., do not have to be added as well)

- Instruct the households on the techniques for fermenting sweet potato biomass The fermentation period to achieve a stable pH was about 2 weeks for sliced-vine-leaves and 3 weeks for sliced-roots

- Show farmers how to preserve the fermented products; if the products are kept in anaerobic conditions created by the air-tight enclosure in plastic, the shelf-life will be extended for up to 6 months without reducing safety and nutrition

- Guide the farmers how to use and mix the fermented feeds with the other materials for pigs with different weight Pigs of 2.5 months or 18 to 20 kg are able to eat the fermented feed In the first two days, the pigs should consume 2 meals per day with the mixture of the fermented mash and bran per day Then they can be fed 3 meals per day (morning, noon and evening)

3.4 Participants

- Food Crops Research Institute (FCRI): Nguyen Van Tuat, Truong Cong Tuyen, Nguyen Dat Thoai, Truong Thi Thuy, Nguyen Phan Anh, Tran Quoc Anh, Do Thi Lieu, and Nguyen Thi Hoai

- The University of Sydney: Les Copeland, Peter Sharp, Richard Trethowan

IV Research results

4.1 Livestock feed production in Bac Giang province

4.1.1 Fermentation of vine-leaves

After about 60 days of growth sweet potato plants are pruned to remove roughly half of the foliage At this stage the storage roots have not developed but if the vines and leaves are cut properly, the subsequent development of the storage roots will be enhanced The fermentation process and the ingredients used for vines and leaves were as recommended by the International Potato Centre (Centro Internacional de la Papa-CIP) The quality of the fermented sweet potato product was evaluated by its visual appearance, consistency of texture, the presence of a sweetish, slightly acidic aroma, the absence of foul odours, and its appeal to livestock

After growing 120 days, farmers can harvest sweet potato roots and collect vine-leaves Roots that are too small or too big roots and damaged roots can be mixed with the vines and leaves for fermentation

It was found that the fermentation process for ingredients of the sliced fresh vine-leaves and sliced roots were convenient, simple and gave a good quality of fermented product Utilisation

of the sweet potato roots could reduce the expenditure for feeding raw materials Good results were obtained when the experiments were carried out in the nine locations in Bac Giang, Thanh Hoa and Quang Tri provinces

The fermentation products from the different ingredients for sweet potato vine-leaves were evaluated in Bac Giang as shown in the Table 1

Table 1 Evaluation of fermented products of sweet potato vine-leaves in Bac Giang, years 2008-2009

Locations Bich Son-Viet Yen Ngoc Chau-Tan Yen Mai Trung-Hiep Hoa

Note:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 90% wilted vine-leaves + 10% rice bran + 0.5% salt

CT2: 97.5% wilted vine-leaves + 2.5% cane molasses + 0.5% salt

CT3: 94% fresh vine-leaves + 6% corn flour + 0.5% salt

Table 1 showed that the fermented product had either good or very good quality with most scores of 4 and 5 All of the households carried out the experiments properly by following the instructions under the supervision of the FCRI staff

In the wards in Viet Yen, Tan Yen and Hiep Hoa, the farmers became familiar with the fermentation technology of sweet potato vine-leaves and obtained finished products with good quality

The comprehensively described technology processes enabled farmers to apply it easily so that the quality of the fermentation products could not be differentiated after using the various ingredient combinations with sweet potato vine-leaves

This means the method is flexible enough for farmers to use the available ingredient materials they have for fermentation of sweet potato vine-leaves depending on the economic and market conditions at the time

4.1.2 Fermentation of sweet potato roots

Table 2 Evaluation of fermented products of sweet potato roots in Bac Giang, years

2008 – 2009

Locations Bich Son-Viet Yen Ngoc Chau-Tan Yen Mai Trung-Hiep Hoa

Note:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 10% root + 89.5% fresh vine-leaves + 0.5% salt

CT2: 25% root + 75% fresh vine-leaves + 0.5% salt

CT3: 50% root + 50% fresh vine-leaves + 0.5% salt

As shown in Table 3, the households at Bich Son ward in Viet Yen town produced the best quality of fermented products in the 15 households The lower scores of 3 in some of the trials

in Ngoc Chau-Tan Ten and Mai Trung-Hiep Hoa were due to damage to the bags from rats and other rodents, so that some of the fermented material was exposed to air The quality of the fermented products in these was decreased due to spoilage by bacteria and mould growing

in the aerobic environment

4.2 Livestock feed production in Thanh Hoa province

4.2.1 Fermentation of vine-leaves

The fermented products of vine-leaves in the three towns of Thanh Hoa were evaluated and shown in the table 3 below

Table 3 Evaluation of fermented products of sweet potato vine-leaves in Thanh Hoa,

years 2008 – 2009

Locations Dong Thanh-Dong

Son

Quang Luu-Quang Xuong

Nguyen Binh-Tinh Gia

Note:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 90% wilted vine-leaves + 10% rice bran + 0.5% salt

CT2: 97.5% wilted vine-leaves + 2.5% cane molasses + 0.5% salt

CT3: 94% fresh vine-leaves + 6% corn flour + 0.5% salt

- The households in Nguyen Binh-Tinh Gia produced the best fermented feed quality with

all scores of 5 The quality was scored from 4 to 5 in Quang Luu and it was 3 in one

household at Dong Thanh-Dong Son

- In all locations, the households followed the same processing protocol for fermentation

experiments and therefore almost all of the products had the same good quality The only

household with a score of 3 was in Dong Thanh-Dong Son, which was due to a leaking

plastic bag

- Since the ingredients for fermentation were simple and the processing technologies were

straight-forward, the farmers were able to produce livestock feeds with uniformly good

quality

4.2.2 Fermentation of sweet potato roots

The fermentation trials of roots and vine-leaves gave many benefits because the farmers in

Thanh Hoa harvested a large number of sweet potato roots in a short time The utilization of

roots was able to save input costs for farmers as an alternative to purchasing rice bran, corn

flour and sugar cane molasses as a carbohydrate source to promote the growth of the right

bacteria for good fermentation In addition, the trails demonstrated how the farmers could

save time and money by not having to buy, transport and store rice bran, corn bran or corn

flour for livestock feed preparation Moreover, consumption of unsalable sweet potato roots

for the animal feed could clear up the field efficiently and quickly The small roots and

residual vine-leaves were combined to produce fermented livestock feed as shown in the

Table 4

Table 4 Evaluation of fermentation products of sweet potato roots in Thanh Hoa, 2008-09

Son

Quang Luu-Quang Xuong

Nguyen Binh-Tinh Gia

Notes:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 10% root + 89.5% fresh vine-leaves + 0.5% salt

CT2: 25% root + 75% fresh vine-leaves + 0.5% salt

CT3: 50% root + 50% fresh vine-leaves + 0.5% salt

- All of the households in Thanh Hoa successfully produced of fermented feed products of

very good quality

- The farmers growing sweet potato as part of Project AUSAID CARD 008/07VIE was

very happy to apply the fermentation technology for livestock feeds Beside the

households that participated these experiments, many others outside the project applied

the root fermentation technique for animal feed

- Based on the fermentation technology for sweet potato root with vine-leaves, the farmers

in the project will try to use sweet potato roots with vine-leaves of other plants such as pea

nut and cassava That is a good approach to utilize the biological yield for livestock

feeding

4.3 Livestock feed production in Quang Tri province

4.3.1 Fermentation of sweet potato vine-leaves

Similar to Bac Giang and Thanh Hoa, the farmers in Quang Tri have a traditional method to

process the livestock feed by cutting and drying the sweet potato leaves The dried

vine-leaves can be preserved and used for feeding over a long time However, the fermented feed

has microbial metabolites (lactic acid, acetic acid, etc.) and biomass (amino acid, protein, etc.)

providing good benefits for nutrition and digestion

In addition, the farmers in Quang Tri found that the ingredients were simple and the

processing process was comprehensively described to be applied Therefore the households of

the project in Quang Tri joined enthusiastically the fermentation technology of sweet potato

vine-leaves for livestock feed The quality of the fermented products was evaluated and

shown in the table 5

Table 5 Evaluation of fermented products of sweet potato vine-leaves in Quang Tri,

2008 – 2009

Locations Vinh Thai-Vinh Linh Gio Hai-Gio Linh Hai Quy-Hai Lang

Note:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 90% wilted vine-leaves + 10% rice bran + 0.5% salt

CT2: 97.5% wilted vine-leaves + 2.5% cane molasses + 0.5% salt

CT3: 94% fresh vine-leaves + 6% corn flour + 0.5% salt

Table 5 shows that the quality of fermented products from vine-leave was not significantly

different

- The farmers in Quang Tri were very happy because they could easily source the raw

materials and quickly learn the fermentation technology in order to produce good feed for

rapid livestock growing

4.3.2 Fermentation of sweet potato roots

The farmers accepted the fermentation models of roots because the harvested yield left a high

ratio of small roots The models in Quang Tri province were evaluated and shown in the table

6 below

Table 6 Evaluation of fermentation products sweet potato roots in Quang Tri, years

2008 – 2009

Locations Vinh Thai-Vinh Linh Gio Hai-Gio Linh Hai Quy-Hai Lang

Notes:

Score range 1-5: 1= very bad; 2 = bad, 3 = medium; 4= good; 5 = very good

CT1: 10% root + 89.5% fresh vine-leaves + 0.5% salt

CT2: 25% root + 75% fresh vine-leaves + 0.5% salt

CT3: 50% root + 50% fresh vine-leaves + 0.5% salt

The fermentation processes of sweet potato roots in the three town of Quang Tri were

extremely successful with the best quality, with all scores at 5

The combination of sweet potato roots and vine-leaves was useful and applicable because it

brought farmers convenience and economic efficiency for livestock feeding

V Conclusion and general comments

5.1 Economic efficiency of using fermented vine-leaves and roots

The use of fermented vine-leaves and roots provided economic benefits to farmers:

- Utilisation of the whole biomass yield of sweet potato

- Significant reduction in expenditure on livestock feed livestock to increase the farmer income At

the CARD Project Forum held on 6 April 2010, representatives from the provinces concerned

spoke of the benefits of fermenting the sweet potato foliage as a value adding process, indicating

that it could reduce the amount of the usual feed used by up to 30-50%

- Help pigs and cattle gain more weight due to the nutritional benefits of the fermented feed, such as

high digestibility (short chain carbohydrates and organic acids) and high protein content (amino

acid and biomass from microbial cells)

- The fermentation processes are applicable at household scale because of simple ingredients and

tools, and comprehensively-described procedures

- Using the fermented feeds is convenient because of a long shelf life and its ready-to-feed nature

for livestock

5.2 Technical challenges for processing and use of fermented feed

- The ingredients need to be mixed well to achieve homogenous distribution of moisture and nutrients for good microbial growth

- The bags need to be packed tightly to minimize the air to promote microbial growth under anaerobic conditions

- Complete consumption of one bag at a time, before opening a new one The bags should be repacked tightly after withdrawing feed, and inspected periodically to check for spoilage

VI Appendixes

6.1 Fermentation process of sweet potato vine-leaves

Step 1: Raw material preparation

- Cut vine-leaves into pieces of 0.2 to 0.5cm using a kitchen knife or a special cutting tool

- Wilt under the sun immediately after cutting to minimize the nutrition loss due to respiration by the fresh vine-leaves

Step 2 Ingredients preparation

- After the vine-leaves are wilted, prepare the additives (rice bran, corn bran, corn flour, cassava starch and salt) as calculated and weighed according to the formula

Step 3 Mixing

- Mix rice bran, corn bran, and corn flour or cassava starch with salt to make a homogeneous mixture

- Mix the additive mixture thoroughly with the cut and wilted vine-leaves

Step 4 Packing

- Pack the mixture tightly into a polyethylene (PE) bag enclosed in a woven polypropylene (WPP) bag The PE layer has low oxygen permeability to create the anaerobic conditions for the growth

of fermentative bacteria The WPP layer keeps the PE layer from breaking and tearing when the mixture is pressed tightly, transported and stored

Step 5 Storage

- Keep the fermented feed in a dry, cool place to prevent damage from insects and rodents If the bag is damaged, the feed will have a bad odour due to spoilage by bacteria and mould The feed can be used after 2 weeks of fermentation, and has a shelf life of about 6 months under good storage conditions

6.2 Fermentation process of sweet potato roots

Step 1 Raw material preparation

At harvest time in the spring and winter season, growers have fresh vine-leaves and roots to prepare the livestock feed

Cut or slice roots to the same size of the cereal grain by hand or by the cutter If using the cutter, the roots have to be pre-cut to the size fitted to the cutter intake

Step 2 Additive preparation