Vitamin E and Oxidative Stability During Storage of Raw and Dry Roasted Peanuts Packaged under Air and Vacuum

ABSTRACT: The relationship between vitamin E and the oxidative stability of raw and dry roasted peanuts was studied during storage at 21°C under air and vacuum. Lipid oxidation was monitored by peroxide values (PVs) and conjugated diene values (CDVs). In air, PV (meq/kg) for roasted peanuts reached 47 by 12 wk, whereas that for raw peanuts was below 2 after 38 wk. Under vacuum, lipid oxidation was significantly retarded ( P < 0.05). Tocopherols of raw and roasted peanuts exponentially decreased with increasing PV. After 12 wk, about 50% of α-tocopherol (α-T) was lost for roasted peanuts under vacuum compared with about 90% under air. For raw peanuts, more than 70% of each tocopherol remained after 38 wk under air and vacuum. In general, α-T showed the least stability in roasted peanuts compared with other tocopherols under the reported storage conditions.     

Preserving sensory attributes of roasted peanuts using edible coatings

Peanut products are susceptible to develop rancid and off‐flavours through lipid oxidation. Preservation of these products is one of the problems in the peanut industry. The purpose of this work was to determine the sensory and chemical stability of roasted peanuts (RP) coated with different edible coatings: carboxymethyl cellulose (RP‐CMC), methyl cellulose (RP‐MC) or whey protein (RP‐WPI) during storage. Sensory attributes and chemical indicators (peroxide and p‐anisidine values, and conjugated dienes) of lipid oxidation were measured during storage. Chemical indicator values and intensity ratings of oxidised and cardboard flavours had lower increase in RP‐CMC, RP‐MC and RP‐WPI during storage than in RP, whereas roasted peanutty flavour showed a lower decrease. The stability of RP‐CMC is about a double longer with respect to RP. These results indicate that edible coatings preserve the sensory properties of roasted peanuts. Carboxymethyl cellulose exhibited the best protecting effect on this product.     

Consumer acceptance of roasted peanuts affected by storage temperature and humidity conditions

Consumer acceptance and intensity ratings of roasted peanuts stored at temperatures of 23, 30, 35, and 40 °C, and water activities (a_w) of 0.33, 0.44, 0.54, 0.67 and 0.75 were determined over time. Consumer acceptance ratings, including overall, appearance, color, and texture were affected by storage water activity and time, but not by storage temperature. Consumer intensity ratings of crunchiness were affected by storage water activity and time, but not storage temperature. Aroma acceptance, flavor acceptance, and roasted peanutty and stale/oxidized/rancid intensity ratings of roasted peanuts were dependent on storage temperature, water activity and time.Shelf-life of roasted peanuts was predicted by all consumer attributes (R²>0.60) and was best predicted by aroma acceptance (R²=0.75). Using contour plots with ratings >5.0 for all acceptance attributes, the shelf-life of roasted peanuts stored at 23 °C and between 0.33 and 0.75 a_w was limited by overall acceptance and decreased by approximately 50% with each 0.1 a_w increase. At accelerated temperatures of 30, 35 and 40 °C, shelf-life of roasted peanuts was predominantly limited by flavor acceptance (>5.0), and to a lesser extent by overall acceptance (>5.0). Shelf-life of roasted peanuts stored at accelerated temperatures decreased by 50% or more with each 0.1 a_w increase.     

Sensory characterisation and oxidative stability of walnut oil

This study was carried out in order to probe the extent of oxidative and flavour stability of walnut oil (WO) under conditions normally used for selling in retail markets, during a period of four months. Fresh WO was characterised by higher intensity ratings of nutty and oily film, and lesser ratings for pungent and astringent attributes. Low and similar values for sweetness and bitterness were also detected. The ratings for negative attributes (oxidised and painty) were close to zero. During the long‐term storage period, the extent of the oil oxidative degradation was more pronounced than flavour attributes deterioration. Peroxide values (PV), conjugated dienes and trienes increased significantly throughout the storage period, whereas tocopherol content and oxidative stability index showed significant reductions. Minor changes were observed in the overall flavour stability. Using a PV of 10 mequiv. O₂ kg^?1 oil as a quality criterion, WO stored in transparent glass bottles, exposed to fluorescent light (1100 Lux) and room temperature conditions, without addition of any antioxidant, could maintain an acceptable quality until two months of storage.     

Enzymatic and Autoxidation of Defatted Peanuts

Ground, blanched, raw, and roasted peanuts with varying oil contents were analyzed for oxidation products. Peroxide values (PV) of blanched, ground raw (BRAW) peanuts, demonstrating enzymatic oxidation, and heat-treated rancid roasted peanuts (RRST), demonstrating autoxidation, exhibited decreases (p ≦ 0.05) with decreasing oil content. The Oxidative Stability Index (OSI) time at 110 °C increased (p < 0.05) with decrease in oil content of raw (BRAW) and roasted (BRST) ground peanuts. A higher OSI indicated more oxidative stability, thereby supporting the hypothesis of higher potential for autoxidation at higher oil contents. In addition, BRST exhibited a shorter OSI than BRAW, indicating slower autoxidation in BRAW. Roasted peanutty odor, burnt odor, and roasted peanutty flavor, rancid/oxidized flavor, and burnt flavor scores of rancid roasted peanuts decreased (p ≦ 0.05) with decreasing oil content.     

Compositional and Mechanical Properties of Peanuts Roasted to Equivalent Colors using Different Time/Temperature Combinations

Abstract: Peanuts in North America and Europe are primarily consumed after dry roasting. Standard industry practice is to roast peanuts to a specific surface color (Hunter L‐value) for a given application; however, equivalent surface colors can be attained using different roast temperature/time combinations, which could affect product quality. To investigate this potential, runner peanuts from a single lot were systematically roasted using 5 roast temperatures (147, 157, 167, 177, and 187 °C) and to Hunter L‐values of 53 ± 1, 48.5 ± 1, and 43 ± 1, corresponding to light, medium, and dark roasts, respectively. Moisture contents (MC) ranged from 0.41% to 1.70% after roasting. At equivalent roast temperatures, MC decreased as peanuts became darker; however, for a given color, MC decreased with decreasing roast temperature due to longer roast times required for specified color formation. Initial total tocopherol contents of expressed oils ranged from 164 to 559 μg/g oil. Peanuts roasted at lower temperatures and darker colors had higher tocopherol contents. Glucose content was roast color and temperature dependent, while fructose was only temperature dependent. Soluble protein was lower at darker roast colors, and when averaged across temperatures, was highest when samples were roasted at 187 °C. Lysine content decreased with increasing roast color but was not dependent on temperature. MC strongly correlated with several components including tocopherols (R² = 0.67), soluble protein (R² = 0.80), and peak force upon compression (R² = 0.64). The variation in characteristics related to roast conditions is sufficient to suggest influences on final product shelf life and consumer acceptability. Practical Application: Peanuts are typically dry roasted to a specified surface color for a given food application; however, it is possible to obtain equivalent colors using different temperatures. This simple observation led to the overall goal of this research which was to determine if peanuts roasted to equivalent surface colors using different temperatures are equivalent from a quality perspective. Several compositional and textural measurements important to product quality differed based on the temperature used to achieve a given roast color. Overall, this study suggests there is good potential to optimize peanut quality by simply adjusting the time/temperature profiles during roasting.     

Physical,chemical and oxidative changes in raw peanuts: Effect of relative humidity

Peanuts are susceptible to oxidative deterioration due to various factors during storage. This research studied the proximate composition (lipid, protein, total sugar, moisture and ash.), composition and content of amino acids and fatty acids, peroxide value (PV), carbonyl value (CV), malondialdehyde content (MDA), protein composition and structure changes in the peanuts stored for 320 days under different relative humidity (RH; 50%, 65% and 80%) conditions. Lipid oxidation was delayed at low RH (50% and 65%) storage conditions. At high RH (80%), the contents of unsaturated fatty acids, amino acids, protein and lipids decreased significantly during storage (P < 0.05), whereas the PV, CV and MDA contents increased significantly (P < 0.05). The CV values of YH-9326 and YH-22 increased by 14.46 and 17.48 times respectively. In addition, the protein structure changed throughout the whole storage period (P < 0.05). This research provides a theoretical reference for maintaining storage quality and extending shelf life.     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

Effects of gamma irradiation dose and short-term storage on phytochemicals,antioxidants, and textural properties of boiled ‘Tainan 9’ peanuts

Boiled peanuts are preferable as a ready-to-eat healthy snack; however, gamma irradiation as a postharvest treatment of raw peanuts may induce unfavourable food components. Hence, the phytochemical, antioxidant, and the texture of boiled ‘Tainan 9’ peanuts pretreated with gamma irradiation (0, 2.5, 5, and 10 kGy) and stored at 29 ± 2 °C for up to 180 days were investigated. Both gamma irradiation and storage time contributed to testa darkening in raw peanuts. In boiled irradiated products, irradiation doses and storage time affected the moisture content (MC), total proteins, total oil, total soluble sugars, and antioxidant capacity (P ≤ 0.05). Total phenolic and flavonoid contents showed an increase at days 90 and decreased at days 180 across all treatments. A positive correlation was observed among ferric reducing antioxidant power (FRAP), total phenolics, and total flavonoids. Gamma irradiation at 10 kGy led to increase of peroxide value (PV) (P ≤ 0.05), but malondialdehyde (MDA) content was unaffected. Textural properties of boiled irradiated peanuts were soft. As a result, gamma irradiation at 5 kGy is recommended for postharvest treatment of raw peanuts with subsequent storage up to 180 days to obtain the eating quality of boiled peanuts with good phytochemicals and antioxidant properties, which is a challenge for food industry.     

Effects of processing conditions and packaging material on the quality attributes of dry‐roasted peanuts

Five different processing conditions of raw shelled unblanched peanuts were investigated. The first two treatments involved soaking the peanuts in tap water for 10 and 30 min respectively, then mixing thoroughly with dry NaCl before roasting. Another two treatments involved soaking the peanuts in saturated brine solution for 10 and 30 min respectively before roasting. Unsalted roasted peanuts served as the control. Packaging and storage studies were carried out by packaging the differently treated dry‐roasted peanuts in four different packaging materials and storing them under three different relative humidities for 3 months at ambient temperature. Proximate composition, NaCl content, peroxide value and thiobarbituric acid value were determined and sensory evaluation tests were carried out. Salting was found to improve the taste, flavour and overall acceptability of dry‐roasted peanuts but had no effect on shelf‐life. Peanuts treated in saturated brine solution for 30 min before roasting were the most preferred. The control packaging material, 18 µm transparent polyethylene, was found to be inadequate for protecting the quality attributes of dry‐roasted peanuts, with mould growth being observed on the 42nd day of storage at 80% relative humidity. However, acceptable results were obtained with 45 µm transparent polypropylene. The mean sensory scores and objective tests were found to be negatively correlated. © 2002 Society of Chemical Industry     

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.     

Effect of Peanut Butter Manufacture on Vitamin E

ABSTRACT: The effect of peanut butter manufacture on vitamin E originating from raw peanuts ( Arachis hypogaea L., runner-type) was determined. Tocopherols were quantified by normal-phase high-performance liquid chromatography. No significant differences were observed in tocopherol (T) values between 1998 and 1999 crop raw peanuts or between raw peanuts and peanut butter except for γ-T ( P > 0.05). Oil and stabilizer added to the roasted peanuts during peanut butter processing provided 4% of α-T in the finished peanut butter. Retention of total tocopherols during peanut butter manufacture was 95%. Mean α-T values (mg/100 g) of commercial peanut products ranged from 12.3 (peanut oil) to 4.1 (dry roasted peanuts).     

Roasted Peanuts and Peanut Butter Quality are Affected by Supercritical Fluid Extraction

Roasted peanuts were extracted using supercritical CO₂ (413.6 bar, 50–60° for 0, 2 or 4 hr). Peanuts were evaluated for shatter, tristimulus color, shear-compression force, moisture, lipid content, and sensory attributes. Extracted nuts were prepared into peanut butter and evaluated for color, relative torque resistance ratio, and sensory attributes. Lipid content decreased from 51.6 to 40.6% during 4 hr extraction. SFE increased shatter, shear-compression force, and Hunter L-value, but decreased hue angle, roasted aroma intensity, moistness of mass, fracturability, and roasted flavor intensity of peanuts. SFE increased the relative torque resistance ratio, and adhesiveness of peanut butter but had little effect upon flavor. SFE may be useful to reduce peanut contaminants and lipids to produce value-added peanut products.     

Coating of Peanuts with Edible Whey Protein Film Containing α‐Tocopherol and Ascorbyl Palmitate

ABSTRACT: Physical properties of whey protein isolate (WPI) coating solution incorporating ascorbic palmitate (AP) and α‐tocopherol (tocopherol) were characterized, and the antioxidant activity of dried WPI coatings against lipid oxidation in roasted peanuts were investigated. The AP and tocopherol were mixed into a 10% (w/w) WPI solution containing 6.7% glycerol. Process 1 (P1) blended an AP and tocopherol mixture directly into the WPI solution using a high‐speed homogenizer. Process 2 (P2) used ethanol as a solvent for dissolving AP and tocopherol into the WPI solution. The viscosity and turbidity of the WPI coating solution showed the Newtonian fluid behavior, and 0.25% of critical concentration of AP in WPI solution rheology. After peanuts were coated with WPI solutions, color changes of peanuts were measured during 16 wk of storage at 25 °C, and the oxidation of peanuts was determined by hexanal analysis using solid‐phase micro‐extraction samplers and GC‐MS. Regardless of the presence of antioxidants in the coating layer, the formation of hexanal from the oxidation of peanut lipids was reduced by WPI coatings, which indicates WPI coatings protected the peanuts from oxygen permeation and oxidation. However, the incorporation of antioxidants in the WPI coating layer did not show a significant difference in hexanal production from that of WPI coating treatment without incorporation of antioxidants.     

Active Banana Flour Nanocomposite Films Incorporated with Garlic Essential Oil as Multifunctional Packaging Material for Food Application

Active plasticized banana flour nanocomposite film (APBNF) incorporated with a different garlic essential oil (GO) content was formed using a solution casting to determine the film properties prior to the investigation of its effectiveness to preserve the roasted peanut quality. The GO concentration was positively correlated with the ultraviolet (UV) light barrier property and antioxidant activity indicating the ability to protect the packed food product from lipid oxidation. Additionally, incorporation of 1 mg/mL GO into APBNF showed the highest antioxidant activity and completely inhibited the growth of Aspergillus flavus. Fourier-transform infrared spectroscopy confirmed the functional group interactions between the film matrix and GO which act as an antioxidant and antimicrobial agent. Thus, APBNF incorporated with 1 mg/mL GO as an active packaging to preserve the quality of roasted peanuts was investigated comparing with a commercial plastic packaging of polyethylene terephthalate/low-density polyethylene (PET/LDPE; PET). The shelf life estimation of roasted peanuts packed in both packaging materials (APBNF and PET) based on the peroxide value (PV) was similar at high storage temperature (45 °C). Therefore, APBNF shows a multifunctional primary food packaging to maintain the quality of roasted peanuts or oily food products.