Quality evaluation of raw ground almond kernels (Prunus dulcis): Effect of active and modified atmosphere packaging, container oxygen barrier and storage conditions

Composition of Nuts and Their Potential Health Benefits-An Overview

The possibility that nut intake may defend human health is an interesting point of view and has been investigated worldwide. Consequently, nuts are commonly promoted as healthy. In recent decades, the number of investigations proposing a correlation between nut consumption and a decrease in the risk of key chronic diseases has continued to increase. Nuts are a source of intake of fiber, and dietary fiber is associated with a reduced occurrence of obesity and cardiovascular diseases. Nuts likewise provide minerals and vitamins to the diet and supply phytochemicals that function as antioxidant, anti-inflammatory, and phytoestrogens agents and other protective mechanisms. Therefore, the main goal of this overview is to summarize current information and to describe the utmost new investigation concerning the health benefits of certain nuts.

Effect of packaging material and oxygen concentration on quality of Ghavoot during the storage

Ghavoot is an Iranian traditional food product that prepared by a combination of several types of plant seeds mixed with sugar. The lack of appropriate packaging caused Ghavoot exposed to environment conditions, which leads to oxidation of this product and reduce its nutritional value and marketability. In this study, different types of packaging materials including nylon, the Polyester/ Aluminum/ polyethylene (PET/AL/PE) and the Polyester /Aluminum / Low-Density Polyethylene (PET/AL/LDPE) with different concentrations of oxygen inside the packaging (zero, 5 and 21%) were used to maintain quality properties of Ghavoot. The results showed that samples stored in the PET/Al/LDPE packaging under vacuum, had fewer moisture changes during storage compared with other treatments, as a result, the least changes in the color parameters of Ghavoot occurred. Increasing the concentration of oxygen inside the packaging resulted in higher peroxide, anisidine and totox values as well as the higher total acidity of the Ghavoot's oil. Keeping Ghavoot in the three-layer PET/Al/LDPE pouches under vacuum condition, caused the lipid oxidation to be delayed during the storage. Results of sensory properties showed that increasing the oxygen concentration inside the packaging caused the average score for product flavor to decrease as a result of rancidity development.

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.

Improving the Shelf Life of Peeled Fresh Almond Kernels by Edible Coating with Mastic Gum

Coating, as a process in which fruits, vegetables, kernels, and nuts are covered with an edible layer, is an environmentally friendly alternative to plastic wrapping, which has been considered the most effective way to preserve them over the long term. On the other hand, prolonging the shelf life results in a reduction of spoilage and therefore achieving a goal that is very important nowadays—the reduction of food waste. The quality of preserved almonds kernels depends on factors such as grain moisture, storage temperature, relative humidity, oxygen level, packaging, and the shape of the stored nuts (along with being peeled, unpeeled, roasted, etc.). The commercial importance of the almond fruit is related to its kernel. Almonds that are peeled (without the thin brown skin) and stored have a shorter shelf life than unpeeled almonds since the reddish-brown skin, rich in antioxidants, may protect the kernels against oxidation. In this study, a bioactive edible coating has been tested, which may provide an effective barrier against oxygen permeation and moisture, thus preserving the quality of peeled fresh almonds by extending their shelf life. Mastic gum, as a natural coating agent, was used to coat the peeled fresh almond kernels in four different concentrations (0.5%, 1.0%, 1.5%, and 2.0% w/v). The effect of mastic gum coating on the quality parameters of the peeled fresh almonds (moisture uptake, oil oxidation, total yeast and mold growth, and Aspergillus species development) was studied during four months of storage. The results showed that mastic gum, as a coating agent, significantly (p < 0.05) reduced moisture absorption, peroxide and thiobarbituric acid indices, total yeast and mold growth, and Aspergillus species development in the peeled and coated fresh almonds, compared to the control, i.e., uncoated fresh almonds, during 4 months of storage, packed at room temperature (25–27 °C) inside a cabinet at 90% humidity. Therefore, mastic gum can be used as a great natural preservative coating candidate with antioxidant and antimicrobial effects.

Comparison of the Oil Quality of Light and Dark Walnuts under Different Storage Conditions

The skin of the walnut kernels can get dark during the pre- and post-harvest stages of the production. Dark kernels are less palatable for most consumers but are still edible and maybe preferable, especially in the ground form, for industrial use. In this study, we investigated the differences between oil oxidation indexes, fatty acid and tocopherol compositions of the oils, total polyphenol contents and antioxidant capacities of the extracts of light and dark walnuts. In addition, we evaluated the effects of packaging under nitrogen and vacuum-packaging techniques and storage temperature on these characteristics of both light and dark walnuts during storage for 6 months. Peroxide values and free fatty acid contents of all samples were higher at the end of storage compared to initial values, being more noticeable at 20°C than at 4°C. Increases in the free fatty acid contents were quite higher in dark walnuts than the light ones (6.1 and 3.1 fold, respectively) and the highest values of conjugated diene and peroxide were determined in the samples packaged under air and stored at 20℃. Dark walnuts had lower total phenolic, α- and γ-tocopherol contents and antioxidant activities compared to the light ones. Total phenolic and tocopherol contents decreased over time. We conclude that due to the antioxidant compounds in the fruit, oxidation parameters of dark walnuts are still acceptable at the end of 6-month storage even in the packages with air and at non-refrigerated conditions.

Genetic characterization of an almond germplasm collection and volatilome profiling of raw and roasted kernels

Almond is appreciated for its nutraceutical value and for the aromatic profile of the kernels. In this work, an almond collection composed of 96 Sicilian accessions complemented with 10 widely cultivated cultivars was phenotyped for the production of volatile organic compounds using a proton-transfer time-of-flight mass spectrometer and genotyped using the Illumina Infinium^®18 K Peach SNP array. The profiling of the aroma was carried out on fresh and roasted kernels enabling the detection of 150 mass peaks. Sixty eight, for the most related with sulfur compounds, furan containing compounds, and aldehydes formed by Strecker degradation, significantly increased during roasting, while the concentration of fifty-four mass peaks, for the most belonging to alcohols and terpenes, significantly decreased. Four hundred and seventy-one robust SNPs were selected and employed for population genetic studies. Structure analysis detected three subpopulations with the Sicilian accessions characterized by a different genetic stratification compared to those collected in Apulia (South Italy) and the International cultivars. The linkage-disequilibrium (LD) decay across the genome was equal to r² = 0.083. Furthermore, a high level of collinearity (r² = 0.96) between almond and peach was registered confirming the high synteny between the two genomes. A preliminary application of a genome-wide association analysis allowed the detection of significant marker-trait associations for 31 fresh and 33 roasted almond mass peaks respectively. An accurate genetic and phenotypic characterization of novel germplasm can represent a valuable tool for the set-up of marker-assisted selection of novel cultivars with an enhanced aromatic profile.

Investigation of decontamination effect of argon cold plasma on physicochemical and sensory properties of almond slices

Cold plasma is a novel technology for surface decontamination. Almond slices can be contaminated with different microorganisms during their production. In the current research, the atmospheric argon plasma treatment (5, 10, 15, and 20 min) was used to decontamination of almond slices surface. Microbial load, Color, peroxide value, hardness, and sensory properties of slices was comprised with untreated samples (control). Descriptive sensory evaluation about color, flavor, crispiness, crunchiness, and hardness of almond slices were performed. According to the results of the microbial tests, Total count, molds and yeasts, and Staphylococcus aureus of almond surface decreased about 2.95 log cfu/g, 1.81 log cfu/g, and 2.72 log cfu/g after 20 min of plasma treatment, respectively, provided that microbial reduction increased more by increasing the treatment time. Coupled with the color evaluation, peroxide value and sensory attributes didn't change during plasma treatment. Having said that, the hardness of slices was changed by increasing treatment time. Furthermore, Principal Component Analysis and cluster analysis were performed for sensory evaluation. In light of the consumer's point of view, firstly 10 min and secondly 15 min plasma treatment can be more desirable.

Effects of chitosan coating enriched with thyme essential oil and packaging methods on a postharvest quality of Persian walnut under cold storage

This study evaluated the effects of edible coatings and different packaging methods on the shelf-life and quality of walnut kernels. It focused on the coatings with chitosan (1%) and thyme essential oil (TEO) at concentra- tions of 500 and 1,000 μl L–1 (CT , CT ) or with chitosan alone (CT). The effects of the coatings was assessed 500 1,000 for different packaging methods (LP, loose packaging; PP, packaging in polypropylene bags; and AP, active packa- ging) as contrasted to control walnuts (C). Walnuts were stored for 120 days in darkness, with relative humidity of 55%, at 4°C. The results showed that the L* index and moisture content of the samples in the chitosan with 500 and 1,000 μl L–1 thyme essential oil in active packaging were maximum, whereas peroxide and conjugated diene values were minimum. The lowest rate of mold growth was observed for the chitosan samples with 500 μl L–1 thyme es- sential oil in active packaging. The best overall acceptability score was related to the samples with chitosan alone and the chitosan with 500 μl L–1 thyme essential oil in active packaging. The chitosan alone and the chitosan with 500 μl L–1 thyme essential oil in active packaging are recommended for storage of kernels at 4°C.

Application of chemometric tools for the comparison of volatile profile from raw and roasted regional and foreign almond cultivars (Prunus dulcis)

In almonds, volatile compounds are major contributors to flavour, being scarce the current knowledge about their volatile profile. Hence, this work intended to characterize the volatile profile, using headspace solid-phase microextraction and gas chromatography-mass spectrometry, in raw and roasted almond cultivars (regional cvs. Amendoão, Bonita, Casanova, Molar and Pegarinhos and foreign cvs. Ferragnès and Glorieta). Overall, 35 compounds were identified, with major chemical classes being alcohols and aldehydes. In raw fruits, benzaldehyde and 3-methyl-1-butanol were key compounds, with roasting changing volatile profiles, increasing release of compounds, with predominance of hexanal and benzaldehyde. Cultivars Glorieta and Molar didn't show significant increase in aldehyde content after roasting, which may indicate higher resistance to heat-caused oxidation. The use of linear discriminant analysis and principal components analysis permitted the recognition of patterns in the volatile profiles, that can be useful for cultivars identification. This work allowed the characterization and monitoring changes caused by roasting of volatile components of less studied almond cultivars, identifying some that can withstand roasting procedures with reduced formation of compounds associated with off-flavours.

Defining the Sensory Profiles of Raw Almond ( Prunus dulcis) Varieties and the Contribution of Key Chemical Compounds and Physical Properties

This study describes the sensory composition of commercial sweet almond varieties across two California growing seasons. It also discusses the relationship between sensory attributes and chemical and physical measures. Raw, whole almonds (43 samples each of 13 varieties in 2015 and 40 samples each of 10 varieties in 2016) were evaluated for their sensory profiles using descriptive sensory analysis. The 2016 samples were also analyzed for macro- and micronutrients, amygdalin, volatile composition (using gas chromatography-mass spectrometry), and physical properties, and the results were modeled with the sensory data. Independence, Sonora, and Wood Colony were harder, more fracturable, and crunchy, whereas Fritz and Monterey were more moist and chewy, reflecting their moisture contents. Aldrich and Fritz were higher in marzipan/benzaldehyde flavor, which is related to amygdalin, benzaldehyde, phenylethyl alcohol, and benzyl alcohol. New insights are provided into sweet-almond composition and the sensorial contribution of headspace volatiles. This assists almond growers and processors in describing and marketing almond varieties.

Review of the Sensory and Chemical Characteristics of Almond ( Prunus dulcis) Flavor

Understanding almond flavor, in terms of both sensory aspects and chemistry, is essential for processors to maintain almond quality and to correctly identify acceptable or unacceptable product. This overview of the sensory and chemical characteristics of almond flavor discusses raw and heat-processed almonds, the volatile compounds generated upon heating, the aroma qualities associated with various odorants, and the use of descriptive sensory analysis for sweet almonds. Flavor development and off-flavors in almonds due to rancidity is also explored. The review examines the existing methods used to assess common nonvolatile as well as volatile indicators of lipid oxidation in almonds and the correlation of these indicators with consumer acceptance. Recent research on the relationship among volatile profile, rancidity indicators, and consumer acceptance is presented.

Effect of packaging method, temperature and storage period on physicochemical and sensory properties of wild almond kernel

This research was performed to monitor the effect of different temperatures (4, 25 and 35 °C) and atmospheres (vacuum, CO₂ and normal air) on physicochemical and sensory properties of wild almond kernel during several weeks' storage. The color, moisture content and sensory analysis of the kernels, peroxide value (PV), 2-thiobarbiotic acid (TBA), conjugated dienes and trienes (CD, CT) and acid value (AV) of the oils were determined in defined time intervals. The results showed that the influence of temperature, time and type of atmosphere on the following parameters were significantly different. At all temperatures studied, AV, PV, TBA and CD/CT of oils from all samples increased with time which was less in the modified atmosphere packaging (MAP) compared with vacuum packaging (VP) and air atmosphere packaging (AAP). At the end of storage, the samples stored under AAP at 35 °C had the highest amount of PV (15.5 meq/kg), TBA (0.056 mg/kg) and CT (0.193 μmol/g), while the samples packaged under MAP at 4 °C had the lowest. Irrespective of packaging type, L* and b* values decreased during storage with a parallel increase of values a* resulting in gradual product darkening, especially in AAP. Sensory analysis also showed the decrease of overall acceptability during the storage among the three packaging systems. In conclusion, the use of MAP was the most effective method for protecting wild almond kernel from deteriorative reactions such as oxidation and hydrolysis.

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.

Chemical and Sensory Characterization of Oxidative Changes in Roasted Almonds Undergoing Accelerated Shelf Life

In almonds, there is no standard method for detecting oxidative changes and little data correlating consumer perception with chemical markers of rancidity. To address this, we measured peroxide values (PV), free fatty acid values (FFAs), conjugated dienes, tocopherols, headspace volatiles, and consumer hedonic response in light roasted (LR) and dark roasted (DR) almonds stored under conditions that promote rancidity development over 12 months. Results demonstrate that, although rancidity develops at different rates in LR and DR almonds, consumer liking was not significantly different between LR and DR almonds. Average hedonic ratings of almonds were found to fall below a designated acceptable score of 5 ("neither like nor dislike") by 6 months of storage. This did not correspond with recommended industry rejection standard of PV < 5 mequiv peroxide/kg oil and FFA < 1.5% oleic. FFAs remain well below <1.5% oleic during storage, indicating that FFAs are not a good marker of rancidity in roasted almonds stored in low humidity environments. Regression of consumer liking to concentration of rancidity indicators revealed that selected headspace volatiles, including heptanal, octanal, nonanal, 2-octenal, 2-heptanone, 2-pentylfuran, hexanal, and pentanal, had a better correlation with liking than did nonvolatile indicators.

Chemical and Sensory Quality Preservation in Coated Almonds with the Addition of Antioxidants

Almonds provide many benefits such as preventing heart disease due to their high content of oleic fatty acid-rich oil and other important nutrients. However, they are susceptible to oxidation reactions causing rancidity during storage. The objective of this work was to evaluate the chemical and sensory quality preservation of almonds coated with carboxymethyl cellulose and with the addition of natural and synthetic antioxidants during storage. Four samples were prepared: almonds without coating (C), almonds coated with carboxymethyl cellulose (CMC), almonds coated with CMC supplemented with peanut skins extract (E), and almonds coated with CMC and supplemented with butylhydroxytoluene (BHT). Proximate composition and fatty acid profile were determined on raw almonds. Almond samples (C, CMC, E and BHT) were stored at 40 °C for 126 d. Lipid oxidation indicators: peroxide value (PV), conjugated dienes (CD), volatile compounds (hexanal and nonanal), and sensory attributes were determined for the stored samples. Samples showed small but significant increases in PV, CD, hexanal and nonanal contents, and intensity ratings of negative sensory attributes (oxidized and cardboard). C had the highest tendency to deterioration during storage. At the end of storage (126 d), C had the highest PV (3.90 meqO2 /kg), and BHT had the lowest PV (2.00 meqO2 /kg). CMC and E samples had similar intermediate PV values (2.69 and 2.57 meqO2 /kg, respectively). CMC coating and the addition of natural (peanut skin extract) and synthetic (BHT) antioxidants provide protection to the roasted almond product.

Antioxidant effects of the monoterpenes carvacrol, thymol and sabinene hydrate on chemical and sensory stability of roasted sunflower seeds

BACKGROUND

Oxidation products and rancid flavors decrease the sensory quality of food products, making them unacceptable to consumers. Synthetic antioxidants are used in many foods to prevent rancidity, though their safety is questioned. Monoterpenes are obtained from essential oils and many of them have shown antioxidant activity. The objective of this study was to evaluate the stability of sensory and chemical parameters in roasted sunflower seeds supplemented with carvacrol, thymol and sabinene hydrate monoterpenes.

RESULTS

Five samples were prepared: control roasted sunflower seeds (RS-C) and sunflower seeds treated with carvacrol (RS-Car), sabinene hydrate (RS-S), thymol (RS-T) and butylated hydroxytoluene (RS-BHT). The three monoterpenes (carvacrol, sabinene hydrate and thymol) provided protection to this food product, inhibiting the formation of oxidative deterioration compounds such as peroxides and hexanal and undesirable off-flavors such as oxidized and cardboard flavors. Sabinene hydrate had greater effect preventing peroxide formation during storage than the other monoterpenes.

CONCLUSION

Carvacrol, sabinene hydrate and thymol could be used as an alternative to synthetic antioxidants for preserving the quality of roasted sunflower seeds.

Effect of phenolic compounds on the oxidative stability of ground walnuts and almonds

This study reports the shift of phenolic compound role from antioxidant to prooxidant in the thermal oxidation of ground walnuts and almonds.

Influence of storage on volatile profiles in roasted almonds (Prunus dulcis)

Hexanal, peroxide value, and lipid hydroperoxides are common indicators of lipid oxidation in food products. However, these markers are not always reliable as levels are dynamic and often can be detected only after significant oxidation has occurred. Changes in the volatile composition of light- and dark-roast almonds were evaluated during storage over 24 weeks at 25 or 35 °C using headspace solid phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS). Several volatile changes were identified in association with early oxidation events in roasted almonds. Hexenal decreased significantly during the first 6 weeks of storage and did not increase above initial levels until 20-24 weeks of storage depending upon the degree of roast. In contrast, levels of 1-heptanol and 1-octanol increased at 16-20 weeks, depending upon the degree of roast, and no initial losses were observed. Seventeen new compounds, absent in raw and freshly roasted almonds but detectable after 6 weeks of storage, were identified. Of these, 2-octanone, 2-nonanone, 3-octen-2-one, 2-decanone, (E)-2-decenal, 2,4-nonadienal, pentyl oxirane, and especially acetic acid increased significantly (that is, >10 ng/g). The degree of roasting did not correlate with the levels of these compounds. Significant decreases in roasting-related aroma volatiles such as 2-methylbutanal, 3-methylbutanal, furfural, 2-phenylacetaldehyde, 2,3-butanedione, 2-methylpyrazine, and 1-methylthio-2-propanol were observed by 4 weeks of storage independent of the degree of roast or storage conditions.

California almond shelf life: lipid deterioration during storage

The effects of storage conditions on the lipid deterioration in California almond nuts and sliced were studied. Natural whole almonds with or without polyethylene (PE) packaging and blanched whole almonds and sliced with PE packaging were stored in 10 different storage conditions which were combinations of different temperatures and relative humidity levels. The peroxide values (PVs), iodine values (IVs), and free fatty acids (FFAs) were monitored during the storage. The PVs in the natural samples did not change noticeably whereas the blanched samples changed greatly, indicating that skins may have played a significant role. The IVs decreased slightly in the 1st 150 d of storage and then leveled off. The slightly faster changes in IVs in the blanched samples coincided with the greater changes in PVs in the blanched samples. The natural samples exhibited much higher FFA levels than the blanched samples after storage. In general, FFA increased with increasing storage time, temperature, and humidity. Highest levels of FFA were observed in the samples stored at high temperature and high humidity.

PRACTICAL APPLICATION

The results reported in this article provide useful information that almond producers and processors could use to develop their storage and transport processes.

Volatile analysis of ground almonds contaminated with naturally occurring fungi

Aflatoxigenic aspergilli inflict major economic damage to the tree nut industry of California, with the highest negative impact to almonds. Aspergilli and fungi in general are known to emit volatiles in varying quantity and composition dependent upon their growth media. The goal of the study was to determine the volatile emission of whole and blanched almonds that had been picked out and labeled as inedible by processors. The aflatoxin content and number of colony forming units of each sample were also determined. A total of 23 compounds were consistently detected and identified. Several volatiles from the blanched almonds demonstrated significant increases when compared to the emissions of whole almonds. Several of these volatiles are considered fatty acid decomposition products and included hexanal, heptanal, octanal, nonanal, 3-octen-2-one, tetramethylpyrazine, and decanal. The almond samples investigated were characteristic of a typical postharvest environment and illustrative of potential contamination within a stockpile or transport container. Volatiles indicative of fatty acid decomposition were predominant in the samples that underwent some form of blanching. The emission amounts of hexanal, heptanal, octanal, and hexanoic acid increased 3-fold in samples contaminated with aflatoxin; however, due to variability between samples they could not be considered as indicator volatiles for aflatoxin content. The emission profile of volatiles from almond kernels contaminated with naturally occurring aspergilli and associated fungi is heretofore unreported.