Developing nutrient profile models: a systematic approach

OBJECTIVE: Nutrient profiling can be defined as the 'the science of categorising foods according to their nutritional composition'. The purpose of the present paper is to describe a systematic and logical approach to nutrient profiling. DESIGN: A seven-stage decision-making process is proposed and, as an illustration of how the approach might operate in practice, the development of a nutrient profiling model for the purpose of highlighting breakfast cereals that are 'high in fat, sugar or salt' is described. RESULTS: The nutrient profile model developed for this paper calculates scores for foods using a simple equation. It enables breakfast cereals to be compared with each other and with other foods eaten at breakfast. CONCLUSION: Nutrient profiling is not new, but hitherto most nutrient profiling models have been developed in an unsystematic and illogical fashion. Different nutrient profiling models are needed for different purposes but a key requirement should be that they are developed using a systematic, transparent and logical process. This paper provides an example of such a process; approaches to validating nutrient profiling models are described elsewhere.     

Testing nutrient profile models using data from a survey of nutrition professionals

OBJECTIVE: To compare nutrient profile models with a standard ranking of 120 foods. DESIGN: Over 700 nutrition professionals were asked to categorise 120 foods into one of six positions on the basis of their healthiness. These categorisations were used to produce a standard ranking of the 120 foods. The standard ranking was compared with the results of applying eight different nutrient profile models to the 120 foods: Models SSCg3d and WXYfm developed for the UK Food Standards Agency, the Nutritious Food Index, the Ratio of Recommended to Restricted nutrients, the Naturally Nutrient Rich score, the Australian Heart Foundation's Tick scheme, the American Heart Association's heart-check mark and the Netherlands tripartite classification model for foods. Rank correlation was assessed for continuous models, and dependence was assessed for categorical models. RESULTS: The continuous models each showed good correlation with the standard ranking (Spearman's rho = 0.6-0.8). The categorical models achieved high chi(2) results, indicating a high level of dependence between the nutrition professionals' and the models' categorisations (P < 0.001). Models SSCg3d and WXYfm achieved higher scores than the other models, implying a greater agreement with the standard ranking of foods. CONCLUSIONS: The results suggest that Models SSCg3d and WXYfm rank and categorise foods in accordance with the views of nutrition professionals.     

Characterization of model melanoidins by the thermal degradation profile

Different types of model melanoidins were thermally degraded, with subsequent identification of the volatiles produced, to obtain and compare the thermal degradation profile of various melanoidins. At first, the volatiles produced from heated glucose/glycine standard melanoidins were compared with glucose/glutamic acid and L-(+)-ascorbic acid/glycine standard melanoidins. In the headspace of heated glucose/glycine melanoidins, mainly furans, were detected, accompanied by carbonyl compounds, pyrroles, pyrazines, pyridines, and some oxazoles. Heating of L-(+)-ascorbic acid/glycine melanoidins resulted in relatively more N-heterocycles, while from glucose/glutamic acid melanoidins no N-heterocycles were formed. In a second part, a chemical treatment was applied to glucose/glycine melanoidins prior to the thermal degradation. Acid hydrolysis was performed to cleave glycosidically linked sugar moieties from the melanoidin skeleton. Nonsoluble glucose/glycine melanoidins were also subjected to an oxidation. The results indicate that the thermal degradation profile is a useful tool in the characterization of different types of melanoidins.     

Extended probability model for dry matter and nutrient accumulation by crops

Accumulation of dry matter and plant nutrients by crops over the growing season is important to resource management for agricultural production and for meeting environmental standards. It is becoming more common in agricultural and environmental management to use mathematical models to describe such systems. In this article, an extended probability model was used to characterize accumulation of dry matter and plant nutrient uptake, both of which exhibited sigmoid behavior with time. Data from field studies included corn (Zea mays L.), tobacco (Nicotiana tabacum), and soybean (Glycine max). For the case of corn, it was shown that maximum total plant dry matter at maturity agreed very closely for the three sites. The ratio of the paramters mean time to standard deviation of the distribution was very similar for dry matter and plant nutrient accumulations, with an average of 3.6 for Wooster, OH and 3.5 for Clayton, NC. The ratio was 4.3 for water reuse at Tallahassee, FL. For tobacco, the ratio was also very similar for dry matter and plant nitrogen (N) and potassium (K), and was 3.2 at Raleigh, NC. The ratio was 2.9 for leaf area of soybeans grown at Gainesville, FL. Data for dry matter and plant nutrient accumulation followed the sigmoid shape of the model rather well. The model also produced the “hump”; often observed in plant nutrient concentration during early stages of growth. The probability model suggests that for the crops studied, growth rate followed a gaussian distribution over the season, at least to first approximation.     

Spatial prediction of soil nutrient in a hilly area using artificial neural network model combined with kriging

It is widely recognized that using correlated environmental factors as auxiliary variables can improve the prediction accuracy of soil properties. In this study, a radial basis function neural network (RBFNN) model combined with ordinary kriging (OK) was proposed to predict spatial distribution of four soil nutrients based on the same framework used by regression kriging (RK). In RBFNN_OK, RBFNN model was used to explain the spatial variability caused by the selected auxiliary factors, while OK was used to express the spatial autocorrelation in RBFNN prediction residuals. The results showed that both RBFNN_OK and RK presented prediction maps with more details. However, RK does not always obtain mean errors (MEs) which were closer to 0 and lower root mean square errors (RMSEs) and mean relative errors (MREs) than OK. Conversely, MREs of RBFNN_OK were much closer to 0 and its RMSEs and MREs were relatively lower than OK and RK. The results suggest that RBFNN_OK is a more unbiased method with more stable prediction performance as well as improvement of prediction accuracy, which also indicates that artificial neural network model is more appropriate than regression model to capture relationships between soil variables and environmental factors. Therefore, RBFNN_OK may provide a useful framework for predicting soil properties.     

Quantitative evaluation of the microbial nutrient sink in soil in relation to a model system for soil fungistasis

A quantitative approach was devised to evaluate the influence of soil microbial activity as a sink for nutrients exuded by fungal spores as a factor in soil fungistasis. The approach was based on measuring the CO₂ evolved from microbial respiration of ¹⁴C-labelled exudates from conidia of Cochliobolus victoriae incubated on soil. The amount of exudate lost by spores on soil was greater than the amount lost by spores incubated on a bed of sand undergoing leaching at a flow rate of 110 ml h^?1. where restriction of germination was similar to that on soil. Increasing flow rates in the leaching system increased spore exudation and reduced germination. Germination of C. victoriae conidia on membrane filters floated on distilled water decreased as the volume of water increased. The results indicate that the microbial nutrient sink of soil is sufficient to impose soil fungistasis.     

Uncertainty in predicting weathering rate and environmental stress factors with the profile model

The PROFILE model is a steady state soil chemistry model which is used to calculate soil weathering rate. The model has also been used to calculate critical loads of acidity and N to forest soils, using the ratio of Ca+Mg+K to total inorganic aluminium in the soil solution as criterion, and to surface waters, using the ANC leached from the soil column as criterion. An uncertainty analysis of the PROFILE model was performed by Monte Carlo analysis, varying input parameter errors individually and simultaneously in ranges of ±10–100%, depending on parameter. The uncretainty in calculation of weathering rate, ANC leaching and ratio of Ca+Mg+K to inorganic Al in the soil solution was studied for three Nordic sites. Furthermore, the effect of uncertainty in estimates of critical load for forest soils was assessed. The analysis shows that the weathering rate can be calculated with high precision, provided that the errors of input parameter are within the range that has been reported in the literature. The model tend to be less sensitive to errors in input parameters for the range of conditions where forest damage is most likely to occur. Critical loads of acid deposition for one site calculated on the basis of the model varies within a largest range of ±40%. A study of one geographical grid included in the Swedish critical loads assessment shows that with the number of calculation points in the grid, the distribution of critical loads will stay stable independently of stochastic errors.     

Fruit quality and nutrient composition of grapevines: a review

Grape quality and its nutrient composition vary depending on agronomical management practices (fertilization, irrigation, weed, and pest control), and agrochemicals treatments (such as kaolin, hormones, and sucrose), viticultural (grape cultivars and varieties, training, pruning, cluster thinning, and trunk girdling), and biotechnological techniques, as well as growth stage and environmental changes (soil, climate, and season). Understanding the mentioned agro-biotechnological techniques assists grape growers and geneticists in breeding grapevines to improve yield, tolerance, quality, and nutraceutical values based on their usage purposes. Thus, this review article focuses on the up-to-date approaches and incentivizes further studies on the unknown mechanisms related to engineering grape flavonoid/phenylpropanoid biosynthetic pathways to improve its health-promoting effects in both grape and human. The engineering/breeding strategies and viticultural practices have been proposed based on the grape usage purposes and environmental conditions.     

Vertical porosity profile of a clay-rich marsh soil

The evolution of clay soil porosity is currently demonstrated via the shrinkage curves in a large water content domain spreading from a shrinkage limit to a liquidity limit. In fact, the parallel between in situ profiles and the shrinkage curves in such a large water content range is difficult to obtain because of the lack of earth pressure in the laboratory tests and in situ limited water contents. The vertical distribution of porosity throughout a clay-rich marsh soil profile was studied in a grassland field with samples taken from the soil surface characterized by water contents near their shrinkage limit down to 2.00 m deep saturated sediments over their liquidity limit. The depth of the plasticity limit isolates a soil in a solid state characterized by a vertical prism-like structure from a plastic to pseudo-liquid state in depth. The porosity was calculated from the measurements of the density of intact samples by double weighing and image analysis of 100 cm² polished sections. The initial structure of clay soil was maintained by impregnation based on water–acetone–resin exchange. An ultraviolet photo luminescent pigment added to the resin allowed the capture of images from which shrinkage cracks and microporosity of the clay matrix were easily separated. The distribution of porosity between the shrinkage crack mesoporosity and the clay matrix microporosity was evaluated after the mathematical decomposition of the grey level curves characteristic of each level. Vertical evolution of the porosity distribution from the soil surface in a solid state to the plastic and pseudo-liquid sediment in depth was presented on the shrinkage curve of the clay material. The measurements point out how the clay matrix microporosity and mesoporosity of shrinkage cracks are complementary and the role of the scale effect on the shrinkage curve. The analysis of images captured on an optical microscope under polarized and analyzed light and the SEM observation of freeze-dried samples demonstrated the isotropic arrangement of the clay particles in typical “honey-comb” architecture in the in situ plastic-to-liquid saturated domain. Eventually the distribution of porosity through the profile results from the evolution of the initial “honey-comb” microstructure of the sediment induced by the desiccation phenomenon. It is governed by the depth of plasticity limit of the clay material and by the depth of the water table.     

Effect of humic substances in nutrient film technique on nutrient uptake

An experiment was conducted to find out how humic substances affected nutrient uptake of plants. The test plants, oregano, thyme, and basil, were grown in nutrient film technique at two pH levels (4.5 and 6.5), in two substrates (peat and perlite), and at three levels of humic substance that was a peat extract (control, low, and high concentration). Nutrient uptake of potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were determined by elemental contents in aerial parts of the plant and its weight. Humic substance had no effect on K, Ca, and Mg uptake but lowered the uptake of Fe, Mn, Zn, and Cu for the three test plants, more pronounced with perlite than peat and more at low pH than at high pH. The lowering of the uptake might be caused by complexation of Fe, Mn, Zn, and Cu by the humic substance and the lower availability of these metals in complexed form than as a cation or as EDTA‐chelate in the case of Fe. It is not clear why the effect of the humic substance on micro‐element uptake is larger at low than at high pH. The complexation is expected to be stronger at pH 6.5 than at pH 4.5. At low pH, the high concentration of humic substance caused a low fresh weight of the shoots, perhaps caused by a toxicity of the humic substance at low pH. This was less pronounced at high pH.     

A model for simulating rock–water interactions in a weathering profile subjected to frequent alternations of wetting and drying

Physically based equations for unsaturated groundwater flow and solute transport have been coupled with kinetic rate laws for mineral dissolution–precipitation, and mass balance/mass action equations for aqueous species, in a numerical model that is capable of simulating rock–water interactions in a weathering profile subjected to fluctuating boundary conditions. A numerical experiment was conducted to demonstrate how incipient soil development may proceed in a warm subhumid environment. The simulation involved a hypothetical coarse-textured parent material that was subjected to frequent wetting and drying during an annual water cycle. The hypothetical weathering profile evolved rapidly; dissolution of primary minerals (enstatite, forsterite, and diopside) and precipitation of secondary clay–minerals (kaolinite and Ca-montmorillonite) occurred monotonically despite the abrupt fluctuations in soil-moisture content. In contrast, the activities of aqueous species and dissolution–precipitation rates of calcite were very sensitive to the changing moisture conditions in the upper part of the profile. Although the simulation involved numerous simplifying assumptions, reasonable results were achieved and the calculated (from the model) rate of chemical denudation fell within the range of contemporary denudation rates determined from the dissolved loads of rivers.     

A model for sorption,flux and plant uptake of cadmium in a soil profile: Model structure and sensitivity analysis

Fluxes of cadmium in a soil profile are simulated by coupling a model for linear and nonlinear equilibrium sorption to an existing hydrological model. The aim is to develop a model for Cd transport in soil systems. A separate flow model is used to calculate the water fluxes, which are then used in an equilibrium sorption model, allowing different Freundlich isotherms to be chosen. The model is tested and a sensitivity analysis is made. The variation of soil compartment sizes gave small changes in the results, which is interpreted as a measure of the solution stability. The factor influencing Cd transport most, according to these simulations, is the sorption isotherm. The degree to which Cd sorbs to soil decides how much will be available in the soil water for plant uptake or transport through the soil to the ground water. Other studied factors such as root distribution and hydrological properties influence the result only to a limited degree. With an application of 10 mg Cd/m² in the given range of Freundlich isotherms, the simulations gave a plant uptake of between 0 and 30% of the applied Cd in two years. At the concentration mainly used in this study (with 10 mg Cd/m² applied), the nonlinear isotherms found in the literature gave Cd lower mobility than the linear isotherms used for comparison. For high Cd concentrations the situation would be the reverse.     

Validating a Simple Equation to Predict and Analyze Organic Anion Charge in Swedish Low Ionic Strength Surface Waters

Acid neutralising capacity (ANC) is substituted by CBALK, a term that has been theoretically introduced in the early 1990s, to evaluate a simple pH equilibrium model used for Swedish surface waters. The CBALK approach with its simple three pK_a organic acid analogue is re-evaluated with a new data set of 900 stream water samples. End-point alkalinity and TOC suffice to predict air equilibrated pH in the range 4.5 to 7.5 within 0.08 pH units. This is equivalent to an error in the charge balance of about 5 ueq L^?1. In the studied pH range it renders more precise predictions than when using ANC. The model equations can be used to estimate the effect of organic carbon or carbon dioxide on ambient pH during episodes as well as for sample quality control.     

Carbon and nutrient dynamics under long-term nutrient management in tropical rice-wheat-jute system

Impacts of 43-year nutrient management on carbon (C) and nutrient dynamics were studied in a rice-wheat-jute system in tropical India. Carbon dynamics was investigated on the basis of its distribution of labile (microbial biomass C, permanganate oxidizable C and water soluble C) and slow pools (Walkley Black oxidizable organic C), its indices (C pool index, lability index) and C management index (CMI) at different soil depths. Nutrient dynamics was judged by major nutrients availability, and related soil enzymatic activities. We studied seven treatments including unfertilized control, 100% NPK (N:P₂O₅:K₂O 60:30:60), 50% NPK, 150% NPK, 100% NP, 100% N, 100% NPK + farm yard manure (10 tonnes FYM ha^?1). Nutrients availability and soil enzymatic activities were significantly increased under balanced fertilization (100% NPK + FYM) over other treatments. Labile, slow and total C was also found highest in 100% NPK + FYM. Enhanced C indices under 100% NPK + FYM over 100% NPK and other treatments signified the importance of long term balanced fertilization on soil C stabilization. Lability indexes were lower at sub-soil (30-45cm). In terms of favourable nutrient dynamics and CMI, balanced application of NPK plus organics were recommend for long term sustainability of rice-wheat-jute system in tropics.     

Macro-invertebrates accelerate litter decomposition and nutrient release in a Hawaiian rainforest

Macro-invertebrates (>2 mm in size) can play a key role in litter decomposition by influencing litter chemistry and other components of the decomposer community, thus affecting rates of decomposition, nutrient release, and primary production. However, in many ecosystems the influences of macro-invertebrates on key ecosystem processes have not been adequately addressed. We investigated the influence of the macro-invertebrate community in litter decomposition and the cycling of nutrients in a young rainforest site on the island of Hawaii by using litter bags with and without 2.5 cm holes to allow or prevent access by macro-invertebrates. Presence of macro-invertebrates increased rates of litter decomposition by 16.9% and rates of nutrient release for N and Mn by 33.2% and 30.3%, respectively. Macro-invertebrate activity thus has a major impact on N release accounting for 3.32 kg/ha/yr. This internal ecosystem transfer of N from the litter is greater than estimates of nitrogen inputs from rain water, dry deposition, volcanic sources, atmospheric dust, and nitrogen fixation for this ecosystem. These findings demonstrate that improved knowledge of the ecosystem effects of macro-invertebrates is necessary to understand how ecosystems function.     

Mineralogy and nutrient desorption of suspended sediments during a storm event

Purpose

This study investigated desorption of potassium (K) and phosphorus (P) from soil and river suspended sediments sampled during a storm event in a Brazilian watershed traditionally used for tobacco plantations.

Material and methods

Suspended sediment samples were collected automatically at the outlet of the watershed and were grouped into three phases: beginning (phase a), middle (phase b) and final stages (phase c) of the storm event. Granulometric and mineralogical characterisation of soils (0 to 0.20 m depth) and suspended sediments was determined, and K and P extractions were performed using a cation and anion exchange resin (CAER) membrane. A kinetic modelling approach was used to estimate the amount of K and P desorbed.

Results and discussion

Clay-sized (<2 μm) content of the soils were all <21 %. Kaolinite, smectite (partially with hydroxy-Al interlayer) and a small amount of illite were found in the clay fraction of the different soils. The clay-sized fractions in sediments of phases a, b and c of the storm event were 49, 52 and 72 %, respectively. Smectite (>90 %) and kaolinite (<10 %) were the dominant clay minerals in the suspended sediments. The values of labile P and potentially available P of suspended sediments were higher than those for soils. In sediments, the highest values of labile P (325 mg kg^?1) and labile K (4,458 mg kg^?1) were found in phase c and in phase a, respectively.

Conclusions

Particle size distribution and clay mineralogy of soils differed from those of suspended sediments collected during the storm event. By comparison with the watershed soils, suspended sediments collected during the storm event were enriched in fine particles composed mainly of smectite, and this may explain their P and K desorption behaviour. This suggests particle size and clay species selectivity processes during the transfer of sediment particles from soils to aquatic systems. The amounts of P and K desorbed from the suspended sediments in the three phases of the storm event were much larger than those desorbed from soils. This indicates that rainfall promoted the transfer of these nutrients to the watercourses.     

Optimum nutrient levels in a container growing medium determined by a saturated aqueous extract

Abstract

Red pine (Pinus resinosa Ait.) seedlings were grown for 15 weeks over a range of nutrient regimes to calibrate a test procedure used for monitoring nutrient status of a common container growing medium. The test was based on a saturated aqueous extract of the growing medium, obtained by suction displacement. Seedling growth and nutrition exhibited typical responses of deficiency, sufficiency, luxury consumption and toxicity over the range of substrate fertility examined. Water extractable nutrients of the growing medium were related to yield and nutrient uptake of the seedlings. Ranges of nutrient levels associated with maximum dry matter production were selected as provisional values for optimum growth of containerized red pine seedlings. The following critical nutrient levels were considered optimum for red pine seedlings managed under similar cultural conditions: 15–65 ppm N (as NH₄ ⁺), 35–95 ppm P, 25–115 ppm K, 30–60 ppm Ca, 15–35 ppm Mg, and electrical conductivity of 1.0–2.2 dS/m.