The protein content in foodstuffs is estimated by multiplying the determined nitrogen content by a nitrogen-to-protein conversion factor. Jones' factors for a series of foodstuffs, including 6.25 as the standard, default conversion factor, have now been used for 75 years. This review provides a brief history of these factors and their underlying paradigm, with an insight into what is meant by "protein." We also review other compelling data on specific conversion factors which may have been overlooked. On the one hand, when 6.25 is used irrespective of the foodstuff, "protein" is simply nitrogen expressed using a different unit and says little about protein (s.s.). On the other hand, conversion factors specific to foodstuffs, such as those provided by Jones, are scientifically flawed. However, the nitrogen:protein ratio does vary according to the foodstuff considered. Therefore, from a scientific point of view, it would be reasonable not to apply current specific factors any longer, but they have continued to be used because scientists fear opening the Pandora's box. But because conversion factors are critical to enabling the simple conversion of determined nitrogen values into protein values and thus accurately evaluating the quantity and the quality of protein in foodstuffs, we propose a set of specific conversion factors for different foodstuffs, together with a default conversion factor (5.6). This would be far more accurate and scientifically sound, and preferable when specifically expressing nitrogen as protein. These factors are of particular importance when "protein" basically means "amino acids," this being the principal nutritional viewpoint.

/pdf/converting-nitrogen-into-protein-beyond-6-25-and-jones-411vf4lh1d.pdf

Converting nitrogen into protein--beyond 6.25 and Jones' factors.

Chemical composition and nutritional value of European species of wild growing mushrooms: A review

https://bibliotecadigital.ipb.pt/bitstream/10198/12061/3/242.pdf

Bioactivity of phenolic acids: metabolites versus parent compounds: a review.

https://digital.csic.es/bitstream/10261/22454/3/SUPERCRITICAL%20FLUID%20EXTRACTION.pdf

Supercritical fluid extraction: Recent advances and applications

Maintenance of equilibrium between free radical production and antioxidant defences (enzymatic and non enzymatic) is an essential condition for normal organism functioning. When this equilibrium has a tendency for the production of free radicals we say that the organism is in oxidative stress. In this situation, excess free radicals may damage cellular lipids, proteins and DNA, affecting normal function and leading to various diseases. In aerobic organisms, the free radicals are constantly produced during the normal cellular metabolism, mainly in the form of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS). Exposition of the organism to free radicals has led to the development of endogenous defence mechanisms to eliminate them. These defences were the response of evolution to the inevitability of ROS production in aerobic conditions. Natural products with antioxidant activity may help the endogenous defence system. In this perspective the antioxidants present in the diet assume a major importance as possible protector agents reducing oxidative damage. Particularly, the antioxidant properties of wild mushrooms have been extensively studied by our research group and by others, and many antioxidant compounds extracted from these sources have been identified, such as phenolic compounds, tocopherols, ascorbic acid, and carotenoids. We will review the compounds identified so far in mushrooms, as well as the mechanism of action involved in their antioxidant properties. Wild mushrooms might be used directly in diet and promote health, taking advantage of the additive and synergistic effects of all the bioactive compounds present.

/pdf/antioxidants-in-wild-mushrooms-3j0nwujyp5.pdf

Antioxidants in Wild Mushrooms

The aim of the study was to determine the contents of mineral elements (Ca, K, Mg, Na, P, Cu, Fe, Mn, Cd, Pb, and Se), vitamins (B1, B2, B12, C, D, folates, and niacin), and certain phenolic compounds (flavonoids, lignans, and phenolic acids) in the cultivated mushrooms Agaricus bisporus/white, Agaricus bisporus/brown, Lentinus edodes, and Pleurotus ostreatus. Selenium, toxic heavy metals (Cd, Pb), and other mineral elements were analyzed by ETAAS, ICP−MS, and ICP methods, respectively; vitamins were detected by microbiological methods (folates, niacin, and vitamin B12) or HPLC methods (other vitamins), and phenolic compounds were analyzed by HPLC (flavonoids) or GC−MS methods (lignans and phenolic acids). Cultivated mushrooms were found to be good sources of vitamin B2, niacin, and folates, with contents varying in the ranges 1.8−5.1, 31−65, and 0.30−0.64 mg/100 g dry weight (dw), respectively. Compared with vegetables, mushrooms proved to be a good source of many mineral elements, e.g., the contents of ...

Contents of vitamins, mineral elements, and some phenolic compounds in cultivated mushrooms.

The basic composition (moisture, total carbohydrates, dietary fiber, crude fat, ash, nitrogen, and protein) and amino acid contents were determined in the cultivated mushrooms Agaricus bisporus/white, Agaricus bisporus/brown, Lentinula edodes, and Pleurotus ostreatus. In addition, nitrogen-to-protein conversion factors were calculated for each species by dividing the sums of amino acid residues with total (Kjeldahl) nitrogen contents. The dry matter contents of mushrooms varied from 7.7% to 8.4%. The dry matter of mushrooms contained large amounts of carbohydrates, from 4.5 (A. bisporus/white) to 5.8 g/100 g fresh weight (L. edodes). L. edodes proved to be an especially good source of dietary fiber (3.3 g/100 g fresh weight); the other mushrooms contained 1.5-2.4 g/100 g fresh weight. Crude fat, ash, and protein (based on amino acid analysis) contents of the mushrooms varied 0.31-0.35, 0.49-0.78, and 1.8-2.09 g/100 g fresh weight, respectively. Mushrooms proved to be good sources of almost all essential amino acids when compared with common vegetables. The mean nitrogen-to-protein conversion factor analyzed in the present study was 4.7 +/- 0.21. When using this factor, a very good estimation of protein contents could be obtained for the main species of mushrooms cultivated in Finland.

Basic composition and amino acid contents of mushrooms cultivated in Finland.

Egg yolk is an excellent source of phospholipids. Egg yolk powder (EYP) contains about 60% lipids, which consist of, on average, neutral lipids (65%), phospholipids (31%) and cholesterol (4%). The utilization of supercritical fluid techniques is a new way to selectively extract and fractionate non-polar and slightly polar components from foods and food products. In this study, we developed pilot-scale production methods for the isolation of high-purity egg yolk phospholipids. The method involves either liquid ethanol or supercritical fluid extraction (SFE) as isolation method and supercritical antisolvent process as precipitation method. EYP was fractionated to lipid- and protein-rich fractions using liquid ethanol or supercritical fluid as an extraction medium. In both cases, the target fraction was phospholipids dissolved in ethanol. From this solution, phospholipids were precipitated using supercritical carbon dioxide as antisolvent. Depending on the process conditions, 72–99% of the precipitate consisted of phosphatidyl choline and phosphatidyl ethanolamine, which appeared in ratios 6:1–7:1. The highest purity of phospholipids was obtained via precipitation of the isolate obtained using two-step SFE.

Isolation and purification of egg yolk phospholipids using liquid extraction and pilot-scale supercritical fluid techniques

Eggs are one of the most important sources of vitamin D in the human diet, and their vitamin D content can be further increased by adding more vitamin D to hen feed. To investigate this issue more closely, we performed two feeding experiments. In both, zero egg samples were collected while the hens were fed regular feeds with a vitamin D content of 1720 or 4280 IU/kg. In experiment 1, egg samples were collected 2, 4, 7, 9, 11, 13, 16, 23, and 30 days after beginning the high-cholecalciferol (11 200 IU/kg) feeding period. In experiment 2, samples were collected 2, 4, 6, 8, 13, 28, 56, 84, 112, 140, and 168 days after beginning the high-cholecalciferol (12 000 IU/kg) diet. The egg samples were then assayed for their cholecalciferol content, and some samples, also for the presence of 25-hydroxycholecalciferol by an HPLC method. Further, the vitamin D-fortified eggs were compared with the controls by a sensory evaluation, by conducting fatty acid and functional analyses (emulsion capacity, gel forming capacity, foaming properties) and by measuring eggshell strength. Because vitamin D can be toxic in high doses, we also performed histopathological tests on the hens at the end of experiment 2. The top cholecalciferol contents in egg yolk (ca. 30 microg/100 g) were reached 8-13 days from starting the high-cholecalciferol diet. After 112 days feeding the cholecalciferol content gradually decreased to ca. 22 microg/100 g. When added to eggs as described above, vitamin D did not affect their sensory or functional properties or their fatty acid composition. Moreover, the cholecalciferol levels used in this study appeared not to affect eggshell strength or to be harmful for hens.

Karoliina Könkö

Papers

Contents of vitamins, mineral elements, and some phenolic compounds in cultivated mushrooms.

Basic composition and amino acid contents of mushrooms cultivated in Finland.

Isolation and purification of egg yolk phospholipids using liquid extraction and pilot-scale supercritical fluid techniques

Effect of cholecalciferol-enriched hen feed on egg quality.

The characterisation of oat lipids produced by supercritical fluid technologies