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Means to Optimize the Nutritional Properties of Starch in Potato Products - Impact on glycaemia, satiety and resistant starch content

Leeman, Margareta LU (2006)
Abstract (Swedish)
Popular Abstract in Swedish

Potatis har varit, och är fortfarande ett viktigt baslivsmedel i svensk kosthållning. Det finns många sorter med olika egenskaper vilket bidrar till dess variationsrikedom. Potatisen är en rik källa till stärkelse, kostfibrer samt vitaminer och mineraler, t ex C-vitamin och järn. En invändning mot potatis ur nutritionell synvinkel är att stärkelsen lätt bryts ned av enzymer i magtarmkanalen. Detta ger upphov till ogynnsamt höga blodsocker- och insulinsvar. Ett sätt att mäta effekten av olika stärkelserika livsmedel på blodsockernivån är glykemiskt index (GI). Blodsockersvaret efter en testprodukt jämförs då med responsen efter en referens med samma kolhydratinnehåll i form av en glukoslösning... (More)
Popular Abstract in Swedish

Potatis har varit, och är fortfarande ett viktigt baslivsmedel i svensk kosthållning. Det finns många sorter med olika egenskaper vilket bidrar till dess variationsrikedom. Potatisen är en rik källa till stärkelse, kostfibrer samt vitaminer och mineraler, t ex C-vitamin och järn. En invändning mot potatis ur nutritionell synvinkel är att stärkelsen lätt bryts ned av enzymer i magtarmkanalen. Detta ger upphov till ogynnsamt höga blodsocker- och insulinsvar. Ett sätt att mäta effekten av olika stärkelserika livsmedel på blodsockernivån är glykemiskt index (GI). Blodsockersvaret efter en testprodukt jämförs då med responsen efter en referens med samma kolhydratinnehåll i form av en glukoslösning eller vitt bröd. På liknande sätt kan ett insulinemiskt index (II) fås. Det är idag allmänt känt att långvariga perioder med hög blodsockernivå (hyperglykemi) i kombination med en stillasittande livsstil kan ge upphov till insulinresistens och andra sjukdomar relaterade till det s k metabola syndromet. Några andra exempel på sjukdomar inom detta kluster är fetma, hjärtkärlsjukdom och typ 2 diabetes. Till potatisens fördelar hör dess relativt höga innehåll av stärkelse som inte bryts ned av enzymerna i magsäck och tunntarm, s k resistent stärkelse (RS). Istället fermenteras den i tjocktarmen under bildning av bl a kortkedjiga fettsyror vilka kan ha positiva hälsoeffekter både lokalt i tarmen och på metabola funktioner, t ex blodets kolesterolhalt.



Syftet med föreliggande arbete var att undersöka stärkelsens biotillgänglighet i potatis med hjälp av både provrörsförsök och måltidsstudier på friska försökspersoner. Olika potatissorter testades, både vanliga sorter som förekommer ute i handeln och genotyper med annorlunda stärkelsesammansättning. Kommersiella potatisprodukter ingick också. Även mättnad inkluderades, då det i litteraturen finns indikationer på att kokt potatis skulle ge upphov till betydligt högre mättnad jämfört med andra livsmedel mätt på energibasis.



Studierna konfirmerade att potatis karaktäriseras av höga blodsockersvar (GI). Inga skillnader sågs mellan olika sorter, knölstorlekar eller lagringstid efter skörd. Ej heller fanns skillnader mellan färskpotatis och vinterpotatis. Däremot kunde det redan relativt höga innehållet av RS ökas med hjälp av tid/temperaturbehandling vid utvalda betingelser. Bara genom att lägga den kokta potatisen i kylen kunde RS-innehållet ökas med 50 % och med hjälp av kylning följt av återuppvärmning kunde RS-innehållet dubbleras jämfört med nykokt potatis. Kylförvaring visade sig också kunna sänka blodsocker- och insulinsvar med 25 %. Genom att servera den kalla potatisen med en vinägrettsås bestående av vitvinsvinäger och olivolja, kunde GI och II sänkas ytterligare. Ett gott och effektivt sätt att sänka potatisens höga blodsockersvar är således att servera potatisen som en kall potatissallad med en vinägrettsås. Genom att byta ut nykokt potatis mot kokt och kylförvarad potatis alternativt kall serverad med vinägrettsås kan den totala glykemiska belastningen för en blandkost sänkas med upp till 30 %.



Även rapporterade mättnadsdata kunde upprepas. Således mättade en portion kokt potatis betydligt bättre än en portion pommes frites med samma energiinnehåll. Dock sågs ingen skillnad mellan kokt potatis och potatismos gjort på pulver trots skillnader i portionsstorlek. Pommes frites hade lägre GI än kokt potatis med tillsats av samma mängd och typ av fett. Detta talar för att det inte är fettkomponenten i sig bakom dess lägre GI utan snarare processbetingelser vid tillverkning och/eller återuppvärmning i ugn av pommes fritesen.



I projektet ingick även genetiskt modifierade potatisar med annorlunda stärkelsesammansättning. Stärkelse består av amylos och amylopektin; två stora molekyler som båda är uppbyggda av glukosenheter. I normal potatis består stärkelsen till ca 75 % av den stora och väldigt grenade molekylen amylopektin medan 25 % utgörs av amylos som både är mindre och mindre grenad. Förhållandet mellan amylos och amylopektin påverkar många egenskaper och bl a finns det studier på spannmålsstärkelser som visar att den enzymatiska tillgängligheten minskar med ökad amyloshalt. Försöken visade att även högamylospotatis avvek på flera sätt jämfört med potatis med normal stärkelsesammansättning. Således var stärkelsehalterna lägre, och sockerinnehållet högre. Vidare hade några av potatisarna med högre amylosinnehåll lägre GI och alla högamylosstärkelser innehöll mer RS.



Sammantaget visar resultaten att potatis, trots sina generellt höga GI-värden kan ha en nutritionell potential i och med de höga RS-halterna som dessutom med relativt enkla metoder kan ökas substantiellt. Vidare är den höga mättnaden en egenskap som kan ha betydelse i viktregleringssammanhang, då det är lättare att hålla sig till en energibegränsad diet bestående av mättande livsmedel. (Less)
Abstract
Despite decreased consumption potatoes still constitute an important staple in the Swedish diet. An objection to potatoes and potato products from a nutritional point of view is the ease by which the starch is digested and absorbed in the gastrointestinal tract. This results in unfavourably high glycaemic and insulinaemic responses (glycaemic index, GI and insulinaemic index, II, respectively). Sustained hyperglycaemia may result in insulin resistance and associated diseases such as diabetes and cardiovascular disease included in the metabolic syndrome. The relatively high content of resistant starch (RS) in boiled potatoes is noteworthy and since RS affects the colonic microflora similarly to dietary fibre, it may have positive effects on... (More)
Despite decreased consumption potatoes still constitute an important staple in the Swedish diet. An objection to potatoes and potato products from a nutritional point of view is the ease by which the starch is digested and absorbed in the gastrointestinal tract. This results in unfavourably high glycaemic and insulinaemic responses (glycaemic index, GI and insulinaemic index, II, respectively). Sustained hyperglycaemia may result in insulin resistance and associated diseases such as diabetes and cardiovascular disease included in the metabolic syndrome. The relatively high content of resistant starch (RS) in boiled potatoes is noteworthy and since RS affects the colonic microflora similarly to dietary fibre, it may have positive effects on colonic and metabolic functions.



The purpose of the present thesis was to characterize the nutritional properties of starch in potato products and to evaluate raw material and optimize processing conditions to improve these properties with particular focus on postprandial glycaemia, satiety and RS content.



Potatoes and potato products were characterized by high GI values (GI = 77-169). No differences were found in predicted GI irrespectively of potato variety, tuber weight or storage time after lifting among varieties with normal amylose contents. Neither were differences found between winter- and new potato varieties. The GI of french fries was 41 % lower compared with boiled potatoes added with the same type and amount of fat. A possible cause may be the particular processing conditions used for manufacturing and/or reheating of the french fries, rather than the fat content per se.



RS content was comparatively high in boiled potatoes (4.5 %, starch basis) and could be increased further in potato tubers by cold storage (7 %) and/or temperature treatment (10 %). Cold storage of boiled potatoes resulted in lower glycaemic and insulinaemic responses (- 25 %). Addition of an oil/vinegar mixture to the cold potatoes reduced GI to 96 (-43 %). Based on current potato consumption; exchanging freshly boiled potatoes for such a pickled potato product would lower dietary GI by approximately 30 %.



Tubers from potato genotypes with increased amylose contents (up to 78 % amylose) contained less starch and had higher content of low molecular weight carbohydrates than tubers with low or normal amylose contents. The over-all predicted GIs for the high-amylose tubers (81 and 83) where somewhat lower than for tubers from their mother lines (118 and 95). The lowest values obtained after processing of common potato varieties were 96 as obtained for boiled, cold stored and pickled potatoes and 77 for french fries. Thus, from a nutritional point of view, there is a potential for genetic modification of potatoes. At present, transgenic potatoes are not approved for human consumption.



Isolated high-amylose starches were characterized by elevated RS contents, (18-34 % RS, total starch basis) compared with starches with normal or low amylose contents (<1 % RS). The results within the thesis altogether suggest retrograded and/or ungelatinized amylose as the main constituent of the RS fraction in time/temperature treated tubers or starches. However, retrograded amylopectin, as obtained after cold storage, or cold storage and subsequent reheating to 30 °C appeared to decrease the rate of starch hydrolysis thus reducing predicted GIs in both tubers and isolated starches with normal or low amylose contents.



Satiating properties of potatoes and potato products were evaluated in meal studies in healthy subjects. Boiled potatoes were considerably more satiating than french fries on an energy equivalent basis, whereas no differences were observed between boiled or mashed potatoes neither in glycaemia nor satiety. The early high postprandial glycaemia for boiled and mashed potatoes coincided with increased satiety; a feature that may have effects on meal termination. In the long-term, highly satiating foods may have positive implications on weight regulation. Compliance to an energy restricted diet is most likely facilitated by the inclusion of highly satiating foods, such as boiled potatoes. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof. Bach Knudsen, Knud Erik, Danish Institute of Agricultural Sciences, Department of Nutrition and Physiology, Tjele, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Näringslära, amylopectin, starch, glycaemic index, resistant starch, Nutrition, vinegar, satiety, amylose, Solanum tuberosum, potato
pages
161 pages
publisher
Division of Applied Nutrition and Food Chemistry, Lund University
defense location
Lecture hall D, Center for Chemistry and Chemical Engineering, Getingevägen 60, Lund Institute of Technology
defense date
2006-09-13 10:15
ISBN
91-628-6844-6
language
English
LU publication?
yes
id
d0070fd2-b966-412a-96e1-eb250aaecc44 (old id 547025)
date added to LUP
2007-10-13 11:17:43
date last changed
2016-09-19 08:45:15
@misc{d0070fd2-b966-412a-96e1-eb250aaecc44,
  abstract     = {Despite decreased consumption potatoes still constitute an important staple in the Swedish diet. An objection to potatoes and potato products from a nutritional point of view is the ease by which the starch is digested and absorbed in the gastrointestinal tract. This results in unfavourably high glycaemic and insulinaemic responses (glycaemic index, GI and insulinaemic index, II, respectively). Sustained hyperglycaemia may result in insulin resistance and associated diseases such as diabetes and cardiovascular disease included in the metabolic syndrome. The relatively high content of resistant starch (RS) in boiled potatoes is noteworthy and since RS affects the colonic microflora similarly to dietary fibre, it may have positive effects on colonic and metabolic functions.<br/><br>
<br/><br>
The purpose of the present thesis was to characterize the nutritional properties of starch in potato products and to evaluate raw material and optimize processing conditions to improve these properties with particular focus on postprandial glycaemia, satiety and RS content.<br/><br>
<br/><br>
Potatoes and potato products were characterized by high GI values (GI = 77-169). No differences were found in predicted GI irrespectively of potato variety, tuber weight or storage time after lifting among varieties with normal amylose contents. Neither were differences found between winter- and new potato varieties. The GI of french fries was 41 % lower compared with boiled potatoes added with the same type and amount of fat. A possible cause may be the particular processing conditions used for manufacturing and/or reheating of the french fries, rather than the fat content per se.<br/><br>
<br/><br>
RS content was comparatively high in boiled potatoes (4.5 %, starch basis) and could be increased further in potato tubers by cold storage (7 %) and/or temperature treatment (10 %). Cold storage of boiled potatoes resulted in lower glycaemic and insulinaemic responses (- 25 %). Addition of an oil/vinegar mixture to the cold potatoes reduced GI to 96 (-43 %). Based on current potato consumption; exchanging freshly boiled potatoes for such a pickled potato product would lower dietary GI by approximately 30 %.<br/><br>
<br/><br>
Tubers from potato genotypes with increased amylose contents (up to 78 % amylose) contained less starch and had higher content of low molecular weight carbohydrates than tubers with low or normal amylose contents. The over-all predicted GIs for the high-amylose tubers (81 and 83) where somewhat lower than for tubers from their mother lines (118 and 95). The lowest values obtained after processing of common potato varieties were 96 as obtained for boiled, cold stored and pickled potatoes and 77 for french fries. Thus, from a nutritional point of view, there is a potential for genetic modification of potatoes. At present, transgenic potatoes are not approved for human consumption.<br/><br>
<br/><br>
Isolated high-amylose starches were characterized by elevated RS contents, (18-34 % RS, total starch basis) compared with starches with normal or low amylose contents (&lt;1 % RS). The results within the thesis altogether suggest retrograded and/or ungelatinized amylose as the main constituent of the RS fraction in time/temperature treated tubers or starches. However, retrograded amylopectin, as obtained after cold storage, or cold storage and subsequent reheating to 30 °C appeared to decrease the rate of starch hydrolysis thus reducing predicted GIs in both tubers and isolated starches with normal or low amylose contents.<br/><br>
<br/><br>
Satiating properties of potatoes and potato products were evaluated in meal studies in healthy subjects. Boiled potatoes were considerably more satiating than french fries on an energy equivalent basis, whereas no differences were observed between boiled or mashed potatoes neither in glycaemia nor satiety. The early high postprandial glycaemia for boiled and mashed potatoes coincided with increased satiety; a feature that may have effects on meal termination. In the long-term, highly satiating foods may have positive implications on weight regulation. Compliance to an energy restricted diet is most likely facilitated by the inclusion of highly satiating foods, such as boiled potatoes.},
  author       = {Leeman, Margareta},
  isbn         = {91-628-6844-6},
  keyword      = {Näringslära,amylopectin,starch,glycaemic index,resistant starch,Nutrition,vinegar,satiety,amylose,Solanum tuberosum,potato},
  language     = {eng},
  pages        = {161},
  publisher    = {ARRAY(0xa108b78)},
  title        = {Means to Optimize the Nutritional Properties of Starch in Potato Products - Impact on glycaemia, satiety and resistant starch content},
  year         = {2006},
}