Walnut Kernels Research Articles

An Approach Regarding the Walnut Oil Obtained in a Press Screw and its Quality

The cold pressed walnut kernels oil is treasured by epicurians. The oil is important for a small segment of the market being used in the gourmet kitchen. The cold pressed oil from walnut kernels (Juglans regia L.) with a content of about 90 % of unsaturated fatty acids in the triglycerides, is a remarkable source ω-3 si ω-6 fatty acids (70 % of the oil triglycerides). The aim of the study was the processing of walnut oil from walnut kernels from the area of Cluj by cold pressing and the influence of the raw material quality upon the oil quality. Walnut kernels from the area of Cluj were used for the oil processing, two, respectively 6 months after harvesting, with a screw press of small capacity (until 5 kg oleaginous seeds/hour). Different pressing heads: 5, 6 and 7mm in diameter were tested. The efficiency of the pressing process and the productivity of the press were determined. For the raw material there were determined the water content (drying at 103±2°C) and the raw fat content (extraction with petroleum ether at 60 °C with Soxhlet extractor). The acid value, the iod value and the fatty acids profile of the triglycerides (GS-methods) were determined for the walnut kernel oil obtained by cold pressing. The naturally dried walnut kernels had water contents of 3,20 and 3,36% and fat contents of 67,14 and 66,36% (two, respectively 6 month after harvesting). The process efficiency by using the press head of 6mm in diameter (65,11 and 66,65 % walnut oil) was better compared to those obtained when the pressing heads used were 5mm (63,86 and 63,87%) and 7mm (62,97%) in diameter. The best pressing productivity was obtained by using the press head of 6 mm in diameter (1,27 kg walnut kernel/h) when walnut kernels were processed two months after harvesting. At the use of the pressing head 5 mm in diameter no big differences occurred between the press productivity values (1,02 and 1,09 kg walnut kernels/h kernels processed two, respectively 6 moths after harvesting). The acid value of the walnut oils was lower than 1,26 mg KOH/g oil, after 6 moths of cold storage, being under the accepted limit value for crude oil (4 mg KOH/g oil). The iodine value was between 127,65 and 138,68. The results of fatty acids profile of the triglyceride from the walnut oil emphasised its alimentary value (8,78 % saturated fatty acids, 19,5 % monounsaturated fatty acids, 60,87 % linoleic acid and 10,56 % linolenic acid–average values). Results were comparable to the literature data. We recommend further studies of the walnut kernels oil processing and quality and the improving of the consumer information program regarding the importance and alimentary value of the different cold pressed oils.

Nutrients in Nut Kernels, Free Amino Acids in English Walnut (Juglans regia) Kernels

Nutrients in Nut Kernels, Free Amino Acids in English Walnut (Juglans regia) Kernels

Oxidation-Reduction Indicators as a Means of Determining Overheating in Walnuts During Dehydration

1. A simple and delicate method is described in which oxidation-reduction indicators are used in buffers of approximate neutrality for the detection of "overheating" in walnuts. 2. Mashed walnut kernels show a strong reducing power which is increased when the nuts are "overheated." 3. It is possible by the method described to study equivalent effects of heating when the temperature and time of heating are varied. 4. "Overheating" is quite as satisfactorily detected in freshly dehydrated nuts as in those held for some time in storage.

Composition of Walnut Trees as Affected by Certain Salts

1. The effects of saline irrigation water upon walnut trees have been studied with reference to the effects upon behavior and growth, and upon the relationship between the inorganic constituents. 2. The continued application of saline irrigation water, to tanks of soil planted to walnut trees, has resulted in a reduced size of the leaves with occasional leaf burn, but no indications of mottle leaf or of walnut "yellows." 3. There exists a gradient in the ash content of the dry matter of walnut trees, which in good soil has its minimum in the rootlets but in saline soil has a minimum near the level of the surface of the soil. 4. The production of a new cycle of growth brings about changes in the relationships of the inorganic constituents of the water-soluble and insoluble fractions of the dry matter. 5. Although the sodium, potassium, and calcium contents of the drainage water of artificially made saline soil, in which walnut trees were grown, were much greater than the magnesium content, yet the woody portion and leaves of the trees contained less sodium, potassium, and calcium but more magnesium than the corresponding parts of control trees in good soil. 6. Walnut trees may absorb large amounts of chlorine and sulphur, much of which may be in organic combination. Persimmon leaves, and citrus leaves and fruit, as well as walnut leaves and fruit have been shown to be able to absorb large amounts of chlorine and sulphur, and to place much of it in organic combinations. The dry matter of leaves of walnut trees growing in soils rich in chlorine may lose one-half or more of its chlorine upon gentle ignition, whereas practically none is lost in the case of badly burned mature walnut husks. 7. Saline soils affect not only the inorganic constituents of the trunk, shoots, and leaves, but also those of the husk and kernel. 8. The effects of the artificially made saline soil upon walnut trees and their fruit are not confined alone to accumulations of chlorine or sulphur, but involve equally important changes in the relationships between the bases within the tissues. 9. When a soil was artificially made saline in controlled tank cultures of walnut trees, the effect of salinity of the soil solution was in the direction of reducing rather than increasing the ash content in the portions of the plant above the soil level, as compared with homologous portions of suitable control trees. 10. The effect of direct sunlight upon walnuts is to bring about an increase in the ash constituents of the dry matter. Such effects, when extreme temperatures also occur, may be so destructive in their action as to cause burning of the husks with its consequent effects upon the marketability of the nuts. 11. Absorption from salt solutions by short shoots with walnuts attached, while the kernels were still in the liquid condition, resulted in a considerable increase in sodium in the kernel portion. Although a considerable amount of chlorine and sulphur was absorbed by the shoots into the walnuts, only the increased sulphur of the husks was retained upon ignition. 12. The ash content of walnut husks increases most rapidly from July to late summer. Mature husks are extremely rich in bases, but the importance of such high concentrations in the physiology of the husk is very little understood. The water solubility of the inorganic constituents of husks changes considerably according to the nature of the soil solution bathing the tree roots. 13. The pH of the juice of young walnut kernels still in the liquid condition was about 5.2. Such juice was extremely rich in inorganic constituents.

Relation of Phosphorus Content to Shriveling of Walnut Kernels

1. The shriveling of walnut kernels takes place after they have passed the liquid condition, have jelled, and are approaching the solid stage. 2. The fresh weight, dry weight, and amount of ash per kernel all decrease with an increase in the shriveling. The ash as a percentage of the dry matter increases with an increase in the amount of shriveling. 3. The amount of each inorganic constituent of the ash per kernel in general shows an increase with the increased age of the kernel. 4. The degree of shriveling has no effect on the total phosphorus content of mature walnut kernels obtained from trees growing on a given soil type. 5. There is a progressive increase in the total phosphorus of walnut kernels as they increase in age. 6. Normal mature walnut kernels obtained from trees growing on widely differing soil types show differences in their total phosphorus content.