Effects of sulphur, nitrogen, phosphorus, potassium, and water stress on dietary fibre fractions, starch, amino acids and on the biological value of potato protein

Abstract

In pot experiments with greatly differing rates of N, P, K, and S, and 3 levels of water, dry matter (DM) yields of tubers varied from 28 to 454 g/pot. Especially P-, K- and S-deficiency reduced the starch content of boiled potatoes, from P from 74 to 59% in DM. S-deficiency increased soluble, insoluble and total digestible fibre (TDF) from about 9 to 12.4% TDF in DM of boiled potatoes. Lignin content of fresh potato DM was increased from 0.7 to 2.0 and from 0.8 to 3.7% by P- and K-deficiency. P-deficiency considerably increased arabinose, galactose, and uronic acid, and decreased glucose content. N-application and P-, K- and S-deficiency increased total- and NO3-N concentrations which varied from 1.32 to 3.67% and from 17 to 400 ppm in DM. Water stress slightly decreased total-N content. Increasing N in DM, due to high N-rates or P- or K-deficiency, decreased concentrations in crude protein (CP) of all essential amino acids, whereas aspartic acid (asparagine) increased. S-deficiency caused particularly strong decreases in concentrations of essential amino acids from 1.28 to 0.49, 1.62 to 1.10, 5.24 to 3.68, and 5.59 to 2.57 g/16 g N of cystine, methionine, lysine and leucine, respectively. Glutamic acid (glutamine) content was increased from 15.7 to 27.6 g/16 g N by S-deficiency. Expressed as g amino acid/kg DM, all amino acid concentrations increased with increasing % N in DM. In N-balance trials with rats, increasing crude protein concentrations in DM of boiled potatoes increased the true digestibility (TD) of the protein from 72 to 90 but decreased the biological value (BV) from 89 to 65. S-deficiency caused a further reduction of the BV to 45. Excluding S-deficiency treatments, linear regression equations between CP concentrations and BV and TD gave correlation coefficients r of -0.94*** and 0.82***, respectively. There was close agreement between changes of BV and concentrations of first limiting amino acids (chemical score), with r = 0.96***.

Rats show differences in some biomarkers of health when eating diets based on ingredients produced with three different cultivation strategies

“…It is well documented that the variation in nutrient content of similar food products is highly dependent on, for example, time of harvest, harvest year, specific field location. 51,52 Thus, when reading the discussion of the present data, it should be noted that the present results of the dietary treatments cannot be applied to the population of 'organic' or 'conventional' foods.…”

The Importance of Nutrient Management for Potato Production Part II: Plant Nutrition and Tuber Quality

“…Beside N, S also has a decisive impact on amino acid formation and hence protein synthesis. Thus, under S deprivation, the proportion of S-containing essential amino acids, namely cysteine and methionine, can be reduced while the proportions of other amino acids can be increased (Eppendorfer and Eggum 1994;Marschner 2012). As described above, acrylamide is formed by reducing sugars reacting with asparagine.…”

Lignin: Characterization of a Multifaceted Crop Component

“…Calcium deficiency induced the activity of enzymes of the phenylpropanoid pathway, which increased the lignin level in soybean roots [79]. Similarly, potassium, phosphorus, and N deficiency increased the lignin content of potato tubers [80], but the authors did not give a physiological explanation for their observation. Manganese (Mn) deficiency appears to be an exception, as it reduced the lignin concentration in wheat roots and shoots [75, 76].…”