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Cassava Processing: Safety and Protein Fortification

Tivana, Lucas LU (2012)
Abstract (Swedish)
Popular Abstract in Swedish

Kassava är ett stärkelserikt livsmedel, jämförbart med potatis. Det produceras främst i jordens tropiska regionerna och är ett viktigt livsmedel i Afrika söder om Sahara. Kassava har stora fördelar som gröda eftersom avkastningen är hög, den har god motståndskraft mot sjukdomar, den växer även på mager jord och den är motståndskraftig mot torka. Emellertid, kassava har också nackdelar: färskt kassava har kort hållbarhet (2 dagar), kassava kan innehålla giftiga substanser och kassava har ett lågt innehåll av protein. Giftig kassava är förhållandevis bitter medan kassava med låg halt giftiga substanser är mer eller mindre söt. Bönderna föredrar ofta bitter kassava med hög halt av de giftiga... (More)
Popular Abstract in Swedish

Kassava är ett stärkelserikt livsmedel, jämförbart med potatis. Det produceras främst i jordens tropiska regionerna och är ett viktigt livsmedel i Afrika söder om Sahara. Kassava har stora fördelar som gröda eftersom avkastningen är hög, den har god motståndskraft mot sjukdomar, den växer även på mager jord och den är motståndskraftig mot torka. Emellertid, kassava har också nackdelar: färskt kassava har kort hållbarhet (2 dagar), kassava kan innehålla giftiga substanser och kassava har ett lågt innehåll av protein. Giftig kassava är förhållandevis bitter medan kassava med låg halt giftiga substanser är mer eller mindre söt. Bönderna föredrar ofta bitter kassava med hög halt av de giftiga substanserna eftersom detta gör dem mer motståndskraftig mot sjukdomar och för att det förhindrar vilda djur från att angripa grödan. Om man äter kassava utan rätt förbehandling kan man bli förgiftad. I Afrika är kassava främst konsumerad inom det självförsörjande jordbruket. Bönderna känner sin kassavas egenskaper och vet hur de skall behandla den.

Det är intressant att utveckla en landsbygdsindustri för förädling av kassava till livsmedel för avsalu eftersom lokalt företagande kan stärka ekonomin för fattiga människor på landsbygden. För att industrialisera tillverkning av livsmedel som bygger på kassava behöver man känna till effektiva metoder för avgiftning och man behöver kunna kontrollera effektiviteten av avgiftningen. Det är också bra om man kan tillverka livsmedel där kassavan kombineras med proteinrika livsmedelsingredienser.

Denna avhandling beskriver och jämför olika metoder att reducera halten toxiska substanser. Metoderna inkluderar kokning, extraktion, fermentering med mögel, soltorkning och rivning med rostning. Alla metoder som inkluderar en effektiv sönderdelning av den färska kassavaroten ger en effektiv avgiftning.

Många av analysmetoderna är komplexa och dyra, särskilt i ett land som Mocambique. Därför ar vi arbetat med en ny enklare metod som bygger på ett regent utvecklat från vitamin B12. Metoden kan användas på olika produkter från kassava.

När man tillsätter protein till kassava erhåller man en produkt med betydligt bättre näringsvärde. Receptet vi undersökte var ett kassava gryn som erhölls genom rostning av riven kassava. I receptet med hög proteinhalt tillsattes soja protein till den sönderdelade kassavan före rostningen. Den produkt som erhölls var hård och mindre attraktiv som livsmedel. Vi kunde identifiera att mikrostrukturen var av typ stärkelse i protein. Genom att ändra processen kunde vi erhålla en produkt med den mer lämpliga mikrostrukturen protein i stärkelse vilket gav en mjukare och mer attraktiv produkt. (Less)
Abstract
Cassava (Manihot esculenta Crantz) is an important and cheap source of carbohydrate in tropical regions, particularly in Sub-Sahara Africa. Cassava as a human food is a good source of energy as it has a comparable high energy density of about 610 kJ/100 g fresh root. The crop has growth advantages and production can take place in soil where other crops such as maize, sorghum and sweet potatoes cannot grow. In the region, cassava is used mainly by the farmers themselves as a subsistence crop because the fresh cassava roots have a short shelf-life (1 to 2 days) after harvest. Consequently, the manufacture of cassava-based industrial products may be of interest as a potential way of boosting the economic value of the crop.

Producing... (More)
Cassava (Manihot esculenta Crantz) is an important and cheap source of carbohydrate in tropical regions, particularly in Sub-Sahara Africa. Cassava as a human food is a good source of energy as it has a comparable high energy density of about 610 kJ/100 g fresh root. The crop has growth advantages and production can take place in soil where other crops such as maize, sorghum and sweet potatoes cannot grow. In the region, cassava is used mainly by the farmers themselves as a subsistence crop because the fresh cassava roots have a short shelf-life (1 to 2 days) after harvest. Consequently, the manufacture of cassava-based industrial products may be of interest as a potential way of boosting the economic value of the crop.

Producing a valuable, nutritional and safe food from cassava involves certain challenges. Cassava has a poor protein content (1% fresh root weight) and contains cyanogenic glucosides that may cause intoxication. This thesis reports on work aimed at overcoming these negative aspects of cassava. The report begins by describing how cassava can be detoxified through processing. Secondly, we propose a new method to facilitate the control of residual toxic compounds in cassava products, and finally we describe a methodology for protein fortification of cassava products while preserving consumer-perceived textural properties.

The cyanogens in cassava are hydrolyzed into volatile free cyanide by allowing contact between the cyanogenic substances localized in the vacuoles of the cells with hydrolyzing enzymes in the cell walls. This can be achieved by damaging the cells mechanically or by fermentation. Studies carried out in Nampula, Mozambique showed that heap fermentation of cassava roots may reduce toxic compounds by up to 96%. Another process used for the removal of toxic compound in cassava roots is shredding of roots, which is also an efficient detoxification method (98% reduction).

Assessment of toxic compounds in cassava products is of crucial importance but most existing methodologies have been shown to depend either on analytical equipment or on laborious and slow procedures. In this study, a simple cyanide detection sensor synthesized from Vitamin B12 is proposed. The new reagent detected the cyanide in seconds and has the advantages of being simple and not toxic.

If the economic value of cassava is to be increased, industrial production of cassava-based products is essential. In this study we chose to process cassava into the traditional product known as rale (a dry, pre-gelatinized and granulated product). Protein was added to this product to improve its nutritional value. Addition of protein to shredded cassava roots before roasting resulted in hard agglomerates, a feature that is undesirable for the product. Pre-treatment of protein suspension such as heating and reducing the pH changes the microstructure in such a way that a protein-fortified product could be obtained without properties that the consumer perceives as negative. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Westby, Andrew, Natural Resources Institute, University of Greenwich, London, UK
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Cassava, Cyanogenic glycosides, aquacyano-cobyrinic acid, processing, amylose, amylopectin, protein, texture
defense location
Lecture hall C, Kemicentrum, Getingevägen 60, Lund University Faculty of Engineering
defense date
2012-10-25 09:15
ISBN
978-91-978122-5-2
language
English
LU publication?
yes
id
1796c2f1-a86a-40f2-a780-ce44dcf9c70e (old id 3124601)
date added to LUP
2012-10-02 14:41:42
date last changed
2016-09-19 08:45:19
@misc{1796c2f1-a86a-40f2-a780-ce44dcf9c70e,
  abstract     = {Cassava (Manihot esculenta Crantz) is an important and cheap source of carbohydrate in tropical regions, particularly in Sub-Sahara Africa. Cassava as a human food is a good source of energy as it has a comparable high energy density of about 610 kJ/100 g fresh root. The crop has growth advantages and production can take place in soil where other crops such as maize, sorghum and sweet potatoes cannot grow. In the region, cassava is used mainly by the farmers themselves as a subsistence crop because the fresh cassava roots have a short shelf-life (1 to 2 days) after harvest. Consequently, the manufacture of cassava-based industrial products may be of interest as a potential way of boosting the economic value of the crop. <br/><br>
Producing a valuable, nutritional and safe food from cassava involves certain challenges. Cassava has a poor protein content (1% fresh root weight) and contains cyanogenic glucosides that may cause intoxication. This thesis reports on work aimed at overcoming these negative aspects of cassava. The report begins by describing how cassava can be detoxified through processing. Secondly, we propose a new method to facilitate the control of residual toxic compounds in cassava products, and finally we describe a methodology for protein fortification of cassava products while preserving consumer-perceived textural properties.<br/><br>
The cyanogens in cassava are hydrolyzed into volatile free cyanide by allowing contact between the cyanogenic substances localized in the vacuoles of the cells with hydrolyzing enzymes in the cell walls. This can be achieved by damaging the cells mechanically or by fermentation. Studies carried out in Nampula, Mozambique showed that heap fermentation of cassava roots may reduce toxic compounds by up to 96%. Another process used for the removal of toxic compound in cassava roots is shredding of roots, which is also an efficient detoxification method (98% reduction). <br/><br>
Assessment of toxic compounds in cassava products is of crucial importance but most existing methodologies have been shown to depend either on analytical equipment or on laborious and slow procedures. In this study, a simple cyanide detection sensor synthesized from Vitamin B12 is proposed. The new reagent detected the cyanide in seconds and has the advantages of being simple and not toxic.<br/><br>
If the economic value of cassava is to be increased, industrial production of cassava-based products is essential. In this study we chose to process cassava into the traditional product known as rale (a dry, pre-gelatinized and granulated product). Protein was added to this product to improve its nutritional value. Addition of protein to shredded cassava roots before roasting resulted in hard agglomerates, a feature that is undesirable for the product. Pre-treatment of protein suspension such as heating and reducing the pH changes the microstructure in such a way that a protein-fortified product could be obtained without properties that the consumer perceives as negative.},
  author       = {Tivana, Lucas},
  isbn         = {978-91-978122-5-2},
  keyword      = {Cassava,Cyanogenic glycosides,aquacyano-cobyrinic acid,processing,amylose,amylopectin,protein,texture},
  language     = {eng},
  title        = {Cassava Processing: Safety and Protein Fortification},
  year         = {2012},
}