Kernels in the shell were compared to bare kernels with pellicles, half nuts, blanched nuts, finely chopped nuts, and roasted nuts. Whole nuts and whole kernels were stable for up to two years of storage provided they had not been exposed to high temperatures. Nuts stored at low temperatures (0 and 5°C) did not lose significant amounts of vitamin E. Increasing surface area by dividing nuts or finely chopping them, increased the loss of vitamin E. Samples that had lower surface areas did not lose much vitamin E and peroxide value was low. Higher roasting temperatures caused losses in vitamin E and increased peroxide values at the beginning and during storage, even when stored at 0°C. Intact nuts and low storage temperatures did not show changes in fatty acid composition. High temperature treatments changed fatty acid composition, mainly decreasing linoleic initially and finally oleic acids.
not find a consistent increase in PV with increasing storage time ( Kiritsakis et al., 1998 ; Yousfi et al., 2008 ), in line with our findings. Fig. 3. Changes in peroxide values [milliequivalents active oxygen (O 2 ) per kilogram oil] of oils
“grassy” or “paint-like” flavors in food ( Frankel, 1983 ). Hydrolysis of triacylgycerides yields free fatty acids. Quantifying the peroxide value, hexanal content, and free fatty acids provides insight into the amount of lipid degradation that has
, water activity has not been commonly used to manage walnut storage. Currently, the walnut industry uses analysis of free fatty acids and peroxide values in extracted walnut oil to quantify the degree of hydrolytic and oxidative rancidity, respectively
acidity ( A ) or peroxide value ( B ) measured according to the Official method (EU 1989/2003 modifying the ECC 2568/91) and the Oxitester. Regression equations: ( A ) y = 1.06x + 0.001, R 2 = 0.996; ( B ) y = 1.09x – 0.21, R 2 = 0.995. Phenolic
determined on the dried sample by nuclear magnetic resonance (Maran-S60; Oxford Instruments, Abingdon, UK) and referred on the basis of dry fruit weight. Olive oil physicochemical analyses (FFAs, peroxide value, ultraviolet absorption characteristics at 232
refined oil. Table 5. Olive oil quality from one sample each of three cultivars (Arbequina, Arbosana, and Koroneiki) harvested in 2013 and analyzed for free fatty acids (FFA), peroxide value (PV), K value of ultraviolet absorption at 232 nm [K232
Rancidity is a major problem during the storage of shelled peanuts and walnuts. Blanched peanuts, blanched dry roasted peanuts, blanched oil roasted peanuts (all of them extra large Virginia variety) and shelled Persian walnut (Chandler variety) were maintained in closed jars at 37 C. Relative humidity was controlled by saturated salt solutions at 20% and 55%. Oxygen concentration was 21% or reduced to 0.1% by flushing with nitrogen.
Samples were taken every 2 weeks for 10 weeks. Peroxide values were measured and volatiles were analyzed to determine the rancidity of the samples. Oxygen concentrations in the jars and nut moisture were also measured.
Dry roasted peanuts were the most susceptible to rancidity. Blanched peanuts, without any roasting process, were the most stable. The results quantified the importance of oxygen as a major factor in rancidity at the relative humidities studied. It was concluded that it is possible to quantitatively control the rancidity process by decreasing the oxygen concentration surrounding the nuts.
Ethephon was applied at 0, 625, 1250, 1875, and 2500 m·gliter-1 in 2 consecutive years to `Arbequina' olive trees to determine its effect on fruit removal with mechanical harvesting and on fruit oil composition. Ethephon increased the mechanical harvesting efficiency by 20%. Ethephon at 1250 and 1875 mg·liter-1 were the optimum treatments, resulting in 63% and 66% of the olives being mechanically harvested, respectively, with a preharvest olive drop of 10% and 11%. Leaf drop (4.6 and 4.8 kg/tree fresh weight, respectively) at these concentrations did not reduce flowering the following year. Oil acidity, peroxide value, and fatty acid composition were affected little by ethephon and the values observed were within the range of normal annual variation. These results suggest that ethephon did not modify oil quality and that its use on traditionally pruned `Arbequina' trees is not economically justifiable. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
Pecans nuts from `Kanza' and `Desirable' cultivars were irradiated with 0, 1.5, and 3.0 kGy using electron beam (E-beam) irradiation and stored under accelerated conditions (40 °C and 55% to 60% RH). Antioxidant capacity (AC), phenolic (TP) and condensed tannin (CT) content, HPLC phenolic profile, tocopherol content, peroxide value (PV), and fatty acid profile were evaluated in kernels after 0, 7, 21, 55, and 134 days of storage. Irradiation had no detrimental effects in AC and TP; however, variation was found throughout storage. Tocopherol content of 1.5 and 3.0 kGy kernels decreased after irradiation, but no further decrease was observed thereafter. Irradiated `Desirable' samples had greater PV than controls, while `Kanza' 1.5 kGy samples had increased PV only after 134 days of storage. No change in fatty acid composition was detected for any cultivar. Color modification induced by storage included a decrease in lightness and yellowness and an initial increase of redness followed by a decrease after 98 days of storage. No differences in phenolic profile were observed after irradiation. Compounds identified by HPLC in hydrolyzed extracts were gallic and ellagic acid, catechin, and epicatechin. In general, beside the decrease in tocopherol content, no detrimental effects were found in antioxidant composition caused by irradiation treatments. While a faster oxidation rate was seen in irradiated kernels for `Desirable' cultivar, no other quality attribute was affected by E-beam irradiation.