Lipid Oxidation and Volatile Compounds of Almonds as Affected by Gaseous Chlorine Dioxide Treatment to Reduce Salmonella Populations

The effects of gaseous chlorine dioxide (ClO₂) treatment, applied to inactivate Salmonella, on lipid oxidation, volatile compounds, and chlorate levels of dehulled almonds were evaluated during a 3 month accelerated storage at 39 °C. At treatment levels that yielded a 2.91 log reduction of Salmonella, ClO₂ promoted lipid oxidation as indicated by increased peroxide values, total acid number, conjugated dienes, and thiobarbituric acid-reactive substances. Furthermore, several chlorine-containing volatile compounds including trichloromethane, 1-chloro-2-propanol, 1,1,1-trichloro-2-propanol, and 1,3-dichloro-2-propanol were identified in ClO₂-treated samples. However, all the volatile chlorine-containing compounds decreased during the 3 months of storage. Chlorate (26.4 ± 5.1 μg/g) was found on the ClO₂-treated samples. The amounts of non-ethanol alcohols, aldehydes, and carboxylic acids increased following ClO₂ treatments. Some volatiles such as 2,3-butanediol that were present in non-treated samples became non-detectable during post-ClO₂ treatment storage. Overall, our results demonstrated that gaseous ClO₂ treatment promoted lipid oxidation, generation of volatiles of lipid origin, and several chlorine-containing compounds.

Agronomical and Physiological Behavior of Spanish Hazelnut Selection "Negret-N9" Grafted on Non-suckering Rootstocks

"Negret" is the most widely planted hazelnut cultivar in Northeastern Spain, where it is highly appreciated by the local kernel marked for its favorable nut traits. Its main disadvantages are the high suckers emission, causing large maintenance costs every year, and its medium-to-low vigor and susceptibility to iron chlorosis. In 2000, a trial to select new vigorous and non-suckering rootstocks for hazelnut was established at IRTA Mas Bové (Spain). The "Negret N-9" selection was grafted onto four clonal rootstocks ("Dundee" and "Newberg" two selections of open-pollinated Corylus colurna seedlings, the low suckering cultivar "Tonda Bianca" and the local selection "IRTA MB-69") and compared to the self-rooted "Negret N-9" as a control. The trial was designed as a randomized complete block with 10 replications and one tree per plot (10 trees per treatment). Plant vigor, suckers emission, yield, and nut and kernel traits have been evaluated over 10 years (2003-2012). During the 2006 to 2010 growing seasons, the qualitative traits of kernels, such as kernel skin color, oil content, and fatty acid profiles, were added to the characterization. Physiological data, such as steam water potential, stomatal conductance, and leaf chlorophyll content, were also evaluated during the 2015 growing season. The results showed that clonal rootstocks had a strong influence on vigor and yield of "Negret N-9." The "Dundee," "Newberg," and "IRTA MB-69" rootstocks showed the highest vegetative growth and the lower suckers emission. The yield was highest in trees grafted on "Dundee" rootstock. In terms of the qualitative traits of kernel which are important to the hazelnut industry, rootstocks increased the oil stability and induced a brown light color in the kernel pellicle versus the brown dark color observed in nuts collected from self-rooted "Negret N-9." The fatty acids profile was also influenced by the grafting combination. Finally, physiological traits indicated a higher overall performances for "Dundee" rootstock, which was generally found to be the best rootstock for "Negret N-9" in the experimental environment.

Almond oil: A comprehensive review of chemical composition, extraction methods, preservation conditions, potential health benefits, and safety

Almond oil, a rich source of macronutrients and micronutrients, is extracted for food flavorings and the cosmetics industry. In recent years, the need for high-quality and high-quantity production of almond oil for human consumption has been increased. The present review examines the chemical composition of almond oil, storage conditions, and clinical evidence supporting the health benefits of almond oil. From the reviewed studies, it appears that almond oil contains a significant proportion of poly and monounsaturated fatty acids, with oleic acid as the main compound, and an important amount of tocopherol and phytosterol content. Some variations in almond oil composition can be found depending on the kernel's origin and the extraction system used. Some new technologies such as ultrasonic-assisted extraction, supercritical fluid extraction, subcritical fluid extraction, and salt-assisted aqueous extraction have emerged as the most promising extraction techniques that allow eco-friendly and effective recovery of almond oil. This safe oil was reported by several clinical studies to have potential roles in cardiovascular risk management, glucose homeostasis, oxidative stress reduction, neuroprotection, and many dermatologic and cosmetic applications. However, the anticarcinogenic and fertility benefits of almond oil have yet to be experimentally verified.

Estimation of oxidative indices in the raw and roasted hazelnuts by accelerated shelf-life testing

To estimate the oxidative stability of the raw and roasted hazelnuts, accelerated shelf-life testing (ASLT) was used at elevated temperatures (55, 65 and 75 °C) at water activity (a_w) of 0.43. Chemical parameters, including peroxide value (PV), para-anisidine value, and total oxidation value were measured to estimate the oxidative stability of the samples using Arrhenius model. In addition, the samples were maintained for 8 months in a real condition at 20-30 °C (long-term shelf-life testing) for validating the results obtained from short-term ASLT. The maximum activation energy (E_a, 78.76 kJ/mol °K) and Q₁₀ (1.871) was obtained for PV in raw hazelnuts, while the minimum E_a (53.36 kJ/mol °K) and Q₁₀ (1.552) were recorded for PV in roasted hazelnuts, indicating the negative effect of roasting process on the oxidative stability of the samples. In order to validate the estimations, the values predicted by short-term ASLT for each oxidation index were plotted versus their corresponding values in actual storage. The results showed good correlation coefficients (R² = 0.91-0.98), confirming the fitness of the Arrhenius model to predict the oxidative indices of the samples during normal storage.

Flavor and Acceptance of Roasted California Almonds During Accelerated Storage

Monitoring oxidative flavor changes in almonds is possible only if the chemical and sensory profile during roasting and storage is first established. Herein, almonds roasted at two different temperatures (115 and 152 °C) were stored at 39 °C for 0 to 12 months and were analyzed by headspace solid-phase microextraction gas chromatography-mass spectrometry, descriptive analysis, and consumer hedonic analysis. Volatile profiles, descriptive sensory profiles, and consumer hedonic scores were analyzed for predictive relationships. Descriptive attributes involving Roasted and Nutty as well as consumer liking were highest in fresh almonds, while flavors typically associated with oxidative rancidity such as Cardboard, Painty/Solvent, Soapy, and Total Oxidized increased during storage. Compounds most important for predicting rancidity-related attributes were lipid oxidation products, including pentanal, hexanal, heptanal, and octanal. Consumer liking was best predicted by similar compounds to those predicting Clean Nutty flavor, including Maillard reaction products such as 2- and 3-methylbutanal, 2-methylpyrazine, and 2,5-dimethylpyrazine.

Impact of almond form and moisture content on texture attributes and acceptability

The objectives of this study were to measure sensory texture attributes of 5 types of almonds (blanched slivered, natural sliced, whole blanched, whole dry roasted, and natural whole) conditioned at 4 different moisture levels, to measure liking of a subset of these products, and to compare the sensory texture measurements with consumer liking ratings. Thirteen panelists trained to evaluate almond texture rated the texture attributes of the 20 almond samples. A panel of 113 almond consumers rated their liking of a subset of 8 of these almonds. Compared with the whole almonds, sliced and slivered almonds had less hardness, less crunchiness, less cohesiveness, less tooth packing, and required fewer chews and swallows to consume. Compared with slivered almonds, sliced almonds were more powdery, had more surface roughness, more loose particles, and were crisper. Compared with slivered almonds, sliced almonds were less hard, broke into fewer pieces, had less moistness and cohesiveness of mass, less fatty film, and required fewer chews and fewer swallows to consume. Dry roasted almonds were generally harder, more crisp, more crunchy, and produced more loose particles than natural almonds, which were, in turn, more hard, crisp, and crunchy than blanched almonds. As moisture content increased, moistness of mass and cohesiveness of mass increased. Crispness, number of pieces, hardness, crunchiness, persistence of crunch, and particulate mass decreased with increasing moisture content. Consumer texture liking ratings were highly positively correlated with the attributes crispness, crunchiness, and persistence of crunch.

PRACTICAL APPLICATION

In addition to roasting and blanching, water content of almonds is important for key texture properties. Almond producers can use this information to provide customers with almonds having texture properties important to consumers.

Roasting and packaging in nitrogen atmosphere protect almond var. Guara against lipid oxidation

The effect of packaging in nitrogen (N2) atmosphere or in air on the quality of peeled and roasted almond var. Guara during storage for 20 weeks at 20 °C ± 1 °C and 65–70% relative humidity (RH) was studied. No changes in the sugar, fat, protein or fiber contents were observed during the storage period nor in color. Only the lipid fraction showed significant changes with the kind of packaging atmosphere. The composition of fatty acids remained unchanged during the 5 month storage in all the samples. Packaging in N2 atmosphere was seen to have a protective effect against the accumulation of conjugated dienes (CD) in peeled almonds, while in roasted almonds, the protective effect was lower and even nil by the end of storage. The contrary effect was observed for the ultraviolet (UV; K270) index which increased more slowly in the roasted samples packaged in N2, while in peeled samples it reached the same levels at the end of storage regardless of the packaging atmosphere. No effect of the packaging atmosphere was observed on the evolution of the peroxide value in the tested samples (peeled or roasted almonds). None of these changes in the lipid fraction was reflected in the final sensory quality of the samples and the taster panel found no changes in the sensory quality in any case.