Amin C. Kapoor

Potato tuber proteins and their nutritional quality

SummaryProteins in Red Pontiac potato tubers were fractionated by two methods. Tuberin was the main protein (71%) obtained by Method I (though perhaps by this method up to 40% of the ‘tuberin’ was albumin), while albumin was about half of the total protein obtained by Method II. The amino acid composition of protein fractions obtained by either method was quite similar. All the protein fractions except prolamine were well balanced in essential amino acids and comparable to FAO reference protein. Methionine was the limiting amino acid of the potato fractions. The chemical score, essential amino acid indices and biological value of albumin, globulin, glutelin and residual protein did not vary significantly. Since all the fractions except prolamine, which is a negligible portion of total protein, are of high nutritional quality, Red Pontiac has high-quality protein.ZusammenfassungKartoffelknollenproteine wurden mittels zweier Methoden fraktioniert. Bei Methode I (Tabelle 1) stellte Tuberin mit 71% des Gesamtproteins die Hauptfraktion dar, Bei Methode II dagegen machte das wasserlösliche Albumin ungefähr die Häfte des Gesamtproteins aus. In beiden Methoden war Prolamin die kleinste Fraktion. Die Extraktionsausbeute beider Methoden war sehr hoch. Ungefähr 9% des Gesamtstickstoffs konnte weder mit der einen noch mit der andern Methode extrahiert werden. Es zeigte sich, dass bei Methode I ein Teil des Albumins durch Sättigung mit 40%igem Ammonsulfat ausgefällt wurde. Dies wurde auch durch Elektrophorese dieser Fraktionen bestätigt (Abb. 1). Die Aminosäure-Zusammensetzung der Proteinfraktionen war bei beiden Methode ähnlich (Tabellen 2 und 3). In den essentiellen Aminosäuren waren Albumin, Globulin, Glutelin und Restanteile gut ausgeglichen. Sie waren mit dem FAO-Referenz-Protein vergleichbar, aber weniger wertvoll als das Eiprotein (Tabelle 4). Alle essentiellen Aminosäuren waren in Prolamin schwach vertreten. Die Aminosäure Methionin war in diesen Fraktionen der beschränkende Faktor (Tabelle 5). Der chemische Wertmass-stab (chemical score), der essential amino acid index (EAA-Index), der Bedarfs-Index und die biologische Wertigkeit von Albumin, Globulin, Glutelin und Restanteil wichen nicht stark voneinander ab. Prolamin war in diesen charakterisierenden Eigenschaften schwach vertreten. Da die Prolamine nur einen sehr kleinen Teil des Gesamtproteins ausmachen und alle andern Fraktionen eine sehr hohe Nährstoffqualität aufweisen, ist das Kartoffeleiweiss im ganzen von hoher Wertigkeit.RésuméLes protéines du tubercule de pomme de terre sont fractionnées suivant deux méthodes. Suivant la méthode I (tableu 1), la tubérine est la fraction la plus importante, formant 71% des protéines totales. Au contraire suivant la méthode II, l’albumine soluble dans l’eau constitue la fraction la plus basse. L’efficacité de l’extraction des deux méthodes est vraiment élevée. Il se pourrait que quelque 9% de l’azote total ne soit pas extrait par l’une et l’autre méthode. II apparait que, dans la méthode I, un peu d’albumine est précipité par du sulfate d’ammonium saturé à 40%. Ceci est également attesté par l’électrophorèse des fractions (fig. 1). La composition en acides aminés des fractions de protéine obtenues par les deux méthodes est semblable (tableaux 2 et 3). Albumine, globuline, gluteline et résidu sont bien équilibrés en acides aminés essentiels (tableau 4). Les teneurs de tous les acides aminés essentiels sont basses dans la prolamine. La méthionine est l’acide aminé limitant dans ces fractions (tableau 5). La composition chimique, l’index des acides aminés essentiels, l’index exigé et la valeur biologique des albumine, gluteline et résidu ne diffèrent pas beaucoup. A cet égard la prolamine est inférieure. Puisque la prolamine ne constitue qu’une très petite partie de la protéine totale et que toutes les autres fractions ont une très haute valeur nutritive, la protéine de pomme de terre dans son ensemble est de haute qualité.

Contents and digestibility of carbohydrates of chickpea and black gram as affected by domestic processing and cooking

Abstract Starch digestibility ( in vitro ) and level of total soluble sugars, reducing sugars, non-reducing sugars and starch in cultivars of chickpea ( Cicer arietinum ), as well as black gram ( Vigna mungo ), varied significantly. The effects of different domestic processing and cooking methods on the contents of starch, sugars and starch digestibility ( in vitro ) of eight varieties of chickpea and four of black gram were investigated. Cooking, autoclaving and germination decreased the starch content and increased the level of total soluble sugars, reducing sugars, non-reducing sugars and starch digestibility of both the legumes. Soaking reduced the sugars considerably but starch only marginally. Autoclaving increased starch digestibility more than 4-fold and 5-fold in chickpea and black gram, respectively. Cooking and sprouting also improved starch digestibility appreciably.

Protein and uric acid contents of cereal grains as affected by insect infestation

Abstract A significant increase was recorded in the levels of total nitrogen, total protein, non-protein nitrogen and uric acid contents of wheat, maize and sorghum grains having 25, 50 and 75% infestation caused by Trogoderma granarium Everts and Rhizopertha dominica Fabricius separately and in mixed population. On the other hand, there was a significant reduction in protein nitrogen and true protein contents of three cereal grains at 75% infestation level but the decrease was non-significant at the 25 and 50% levels of grain infestation as compared to control (uninfested grains). Both insect species produced uric acid contents above acceptable limits (10 mg/100 g) even at 50% infestation levels in three cereal grains. Variations in contents of nitrogenous compounds during storage (1, 2 and 4 months) were marginal.

Available carbohydrates of cereal grains as affected by storage and insect infestation

Total soluble sugar, reducing sugar, non-reducing sugar and starch contents of wheat, maize and sorghum grains were affected adversely at 25, 50 and 75% insect infestation caused byTrogoderma granarium Everts andRhizopertha dominica Fabricius, separately and mixed population.R. dominica caused significant (P<0.05) reduction in available carbohydrates at 50 and 75% infestation levels whereasT. granarium achieved similar effect at 75%. Mixture of both insect species caused intermediate losses. Storage of cereal grains up to 4 months resulted in substantial increase in sugars and decrease in starch content, but storage for a shorter period of time did not cause any significant changes in levels of carbohydrates.

Protein digestibility (in vitro) of chickpea and blackgram seeds as affected by domestic processing and cooking.

Protein digestibility (in vitro) of grains of chickpea (Cicer arietinum) and blackgram (Vigna mungo) cultivars varied from 48 to 53% and 52 to 58%, respectively. Soaking, cooking (both of unsoaked and soaked seeds), autoclaving and sprouting improved significantly the protein digestibility of all the cultivars of chickpea and blackgram. Autoclaving was found to be most effective followed by cooking and sprouting; cooking of sprouts had only marginal effect. Protein digestibility was higher when soaked instead of unsoaked grains were cooked.

Amino acid composition and chemical evaluation of protein quality of cereals as affected by insect infestation

A significant decrease in essential amino acids of wheat, maize and sorghum was observed due to grain infestation caused by mixed populations ofTrogoderma granarium Everts andRhizopertha dominica Fabricius (50:50). Non-essential amino acids were also adversely affected. Among the essential amino acids, maximum reduction was found in methionine, isoleucine and lysine in infested wheat, maize and sorghum grains, respectively. Lysine, with lowest chemical score in uninfested and infested grains of three cereals, is the first limiting amino acid. Insect infestation caused significant (p<0.05) reduction in the chemical score of all the essential amino acids, yet did not change the position of first and second limiting amino acids in wheat and sorghum. However, in case of maize, isoleucine became the second limiting amino acid. Infested grains also showed substantial reduction in essential amino acid index, calculated biological value and requirement index.

Evaluation of some plant products against Trogoderma granarium Everts in sorghum and their effects on nutritional composition and organoleptic characteristics

The efficacy of neem, citrus, garlic and podina powders and neem oil at 1 and 2% level (w/w) in sorghum grains was evaluated against larvae of Trogoderma granarium. Neem kernel powder and neem oil completely prevented damage by an introduced larval population. In other treatments, grain damage was noticeable after 3 months, although significantly less than in untreated grains. Thereafter, the percentage of damaged kernels increased progressively and reached as high as 29% (neem leaf), 44% (citrus), 56% (podina) and 71% (garlic) compared to 85% in the control after 6 months. Nutritional composition viz., moisture, ash, fibre, fat, protein and carbohydrates of treated grains remained unaffected after 1 month of storage. After 6 months, changes in nutritional composition were proportional to insect damage. Chapatis (unleavened bread) prepared from flour of treated grains after 1 and 6 months were of normal colour, appearance and texture, but in all cases, their taste, aroma and overall acceptability were adversely affected either by insect infestation or plant products or their combination.

Evaluation of some plant products against Trogoderma granarium Everts in stored wheat and their effects on nutritional composition and organoleptic characteristics of treated grains

Abstract Neem (Azadirachta indica) oil and powders of neem leaf and neem kernel, citrus (Citrus limon) leaf, garlic (Allium sativum) bulb, podina (Mentha spicata) leaf were used in wheat grains at the 1 % and 2% level (w/w) against larvae of Trogoderma granarium Everts. Neem products completely prevented damage by an introduced larval population. In other treatments grain damage was noticeable after 3 months, although significantly less than in untreated grains. Thereafter, damage increased progressively and reached as high as 45% (citrus), 46% (podina) and 72% (garlic) after 6 months. Nutritional composition, viz. moisture, ash, fibre, fat, protein and carbohydrates of treated grains after 1 month, remained unaffected. After 6 months, changes in the level of nutritional compounds were proportional to insect damage. Neem products did not produce any adverse effect on nutritional composition. ‘Chapatis’ made from flour of treated grains after 1 month did not show adverse effects on colour, appearance and t...

Mineral contents of cereal grains as affected by storage and insect infestation

There were substantial losses in thiamine, riboflavin and niacin contents of wheat, maize and sorghum grains at three infestation levels (25, 50 and 75%) caused by releasing two insect species viz.,Trogoderma granarium andRhizopertha dominica separately and mixed population. Losses were to the extent of 65 to 69% (thiamine), 50 to 67% (riboflavin) and 10 to 32% (niacin) due toT. granarium and 23 to 29% (thiamine), 13 to 18% (riboflavin) and 4 to 14% (niacin) due toR. dominica at 75% level of infestation in three cereal grains. Storage of grains (1–4 months) in insect free conditions did not show appreciable changes in the vitamin contents.

Effect of storage and insect infestation on protein and starch digestibility of cereal grains

Protein and starch digestibility of wheat, maize and sorghum grains increased marginally during storage, except for starch digestibility of sorghum which increased significantly (P<0.05) after 4 months of storage. Protein and starch digestibility of three cereal grains having 25, 50 and 75% grain infestation caused by Trogoderma granarium Everts and Rhizopertha dominica Fabricius separately and in mixed form were affected significantly (P<0.05) and adversely. T. granarium, primarily a germ feeder, reduced protein digestibility of wheat and maize more than did R. dominica or a mixed population of both insect species. By contrast, R. dominica, an endosperm feeder, reduced starch digestibility of three cereal grains compared with T. granarium and a mixed population. The reduction in digestibility was dependent on the distribution of proteins and starch in seed components as well as feeding preferences of insects.