FLUIDIZED-BED SYSTEM FOR WHEY PROTEIN FILM COATING OF PEANUTS

Complete peanut‐surface coverage and strong adhesion are necessary for whey protein‐based oxygen barrier coatings to be totally effective in reducing the oxidative rancidity of peanuts. Peanuts coated with a fluidized‐bed coating system attained practically complete coverage, and coating efficiency results were consistent and reproducible. Addition of surfactant to the coating solution improved whey protein coating efficiency on blanched/roasted peanuts coated with a bench‐scale fluidized‐bed coating system. A lower level of surfactant addition to the coating solution was required to attain complete coverage, compared with previous studies on dip coating and pan coating of peanuts. Addition of surfactant to the coating solution and peanut preroughening both imparted good coating adhesion for fluidized‐bed‐coated peanuts. Compared with pan coating, fluidized‐bed coating required application of a greater amount of coating solution because of the loss of coating solution to the fluidized‐bed column wall during spraying. Overall, fluidized‐bed coating required a shorter processing time and provided the peanuts with better coating efficiency and adhesion. These results suggest that a fluidized‐bed coating system is a viable alternative coating process for whey protein coating of peanuts.     

IMPROVEMENT OF OXIDATIVE STABILITY OF ROASTED PEANUTS BY EDIBLE COATINGS AND ULTRASONICATION

In this study, an innovative method was developed to improve the shelf life of roasted peanuts. Sonication was combined with edible coating for enhancing the oxidative stability of roasted peanuts. Georgia green runner peanuts were roasted, subjected to sonication and then coated with whey protein isolate (WPI), ZEIN and carboxymethyl cellulose (CMC). Relative to the control, the oxidative stability of roasted-coated samples was improved by 80, 38 and 5% for CMC, WPI and ZEIN coating, respectively, while roasted-sonicated-coated samples were improved by 91, 52 and 27% for CMC, WPI and ZEIN coating, respectively. Sonication prior to coating resulted in 11, 14 and 22% improvement beyond the CMC, WPI and ZEIN coatings, respectively. Texture analysis showed there were no significant differences ( P <  0.05) in peanut texture between the treated and the control. Color results showed the HunterLab color parameters L, a, and b for most of the treatments did not have significant differences ( P <  0.05) compared with the control.

PRACTICAL APPLICATIONS

Edible coatings used in this study (carboxymethyl cellulose, whey protein isolate and ZEIN) were capable of acting as oxygen barriers to reduce peanut lipid rancidity. This research demonstrated the potential of power ultrasound to remove lipids from the peanut surfaces and improve coating adhesion. The texture and the color of coated peanuts did not change over the storage period. This study indicated that edible coatings in combination with sonication provided an alternative way for improving the oxidative stability and eventually the shelf life and quality of roasted peanuts.     

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.     

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).     

Changes in Roasted Peanut Flavor and Other Quality Factors with Seed Size and Storage Time

Peanut seed size and time in storage have been investigated as to their influence on roasted flavor, peanut butter color. Blanchability of roasted peanuts, oxidative stability and iodine value of raw peanuts. Seed size had a significant effect on roasted flavor and peanut butter color with constant roasting time and with roasting to a uniform peanut butter color. Blanchability of the seed after roasting was also significantly affected by seed size as well as storage time. Oxidative stability of the raw peanuts showed a general tendency to decrease with seed size and storage time. Iodine values were significantly higher in the smallest seed size but storage time did not affect iodine values. The data suggest that inferior quality is being introduced into marketing channels through use of a 5.95 mm screen size as a minimum for grading U.S. No. 1 Virginia-type peanuts.     

吐温辅助水剂法制备花生油的原料预处理工艺研究

花生水剂法提油过程中容易形成大量乳状液导致花生清油提取率降低,这可能与其原料特性密切相关。本文探究了花生种类、花生浆储藏条件和花生红衣对花生清油提取率的影响。首先比较了四种不同种类花生的水剂法清油提取率,并通过制备花生蛋白模拟乳状液比较其乳化性质。将花生浆在不同温度下放置0、2、4、6、8 d,进一步以0.5%吐温20溶液（水作为参照）提取花生油脂。结果表明,大白沙（陈）花生的水剂法清油提取率最高,蛋白乳化性质较好。采用纯水或0.5%吐温20溶液提取,花生浆合适的储藏时间（2~6 d）和储藏温度（室温或37℃）能促进油脂相互聚集并最终提高花生清油提取率;但随着储藏时间的延长,吐温辅助破乳的效果有所降低。经过烘烤脱红衣处理后,花生清油提取率显著下降（P<0.05）。     

Tocopherol content,peroxide value and sensory attributes in roasted peanuts during storage

The objective of this study was to determine changes in tocopherol content, peroxide value (PV) and sensory attributes from roasted peanuts during storage at 40 °C. There were no differences in tocopherol contents between roasted and raw peanuts except in α‐tocopherol content that decreased after roasting. All tocopherol contents decreased during storage. On the contrary, lipid oxidation indicators such as PV and the intensity ratings of oxidised and cardboard flavour increased during storage. On the other hand, the intensity ratings of roasted peanutty flavour decreased with storage time. Good correlations were observed between tocopherol contents and PVs. Tocopherol contents could be used as indicator of oxidative state in peanut products.     

Application of High-Power Ultrasound to Improve Adhesion of Honey on Roasted Peanuts to Improve Oxidative Stability

The extent of honey-coating retention on the surface of sonicated peanuts was studied to evaluate the efficacy of sonication to improve adhesion of honey on peanuts. Samples (150 g each) were sonicated in 450 ml petroleum ether for 5, 10, and 15 min. Following sonication, 25 ml of honey was poured and stirred over the peanuts then roasted in an oven at 177 °C for 10 min. Honey adhesion was determined by measuring the weight of 50 g peanuts before and after coating. The effect of honey and sonication on oxidative stability was measured every 7 days by oxidative stability instrument. The results showed that the weight of honey coating was 7, 16, 19, 21, and 21 g on the control, dipped, 5-, 10-, and 15-min sonicated sample, respectively. Sonication improved adhesion of honey on peanuts by 64%, 68%, and 67% after 5, 10, and 15 min of sonication, respectively, relative to the control. Oxidative stability of dipped, 5-, 10-, and 15-min sonicated samples was improved by 22%, 36%, 46%, and 32%, respectively, in relative to the control. Therefore, removing lipids from peanut surface by high-power ultrasound improved adhesion of honey coating and the oxidative stability.     

Peanut varieties with reduced Ara h 1 content indicating no reduced allergenicity

Peanut allergy is a major cause of food‐induced severe anaphylactic reactions. To date, no medical care is available to prevent and treat peanut allergy and therefore hypoallergenic peanut varieties are of considerable health political and economic interest. Major allergens that induce IgE‐responses in peanut‐sensitive patients are Ara h 1, Ara h 2 and Ara h 3/4. In order to identify hypoallergenic peanuts, commercially locally available peanut varieties were screened for their allergen content. Ara h 1‐deficient peanuts from Southeast Asia were identified by SDS‐PAGE, immunoblotting, inhibition assays and ELISA. 2‐D PAGE analyses demonstrated the different compositions of the tested extracts and revealed a number of variations of the allergen patterns of peanuts from different varieties. Mediator release experiments of these peanut extracts demonstrated similar allergenicities as compared with standard peanut extract. These results indicate that the allergenicity of peanuts with reduced Ara h 1 content might be compensated by the other allergens, and thus do not necessarily cause a reduction of allergenicity.     

The natural skin coating of the apple and its influence on scald in storage. II. Free fatty acids and carbonyl compounds

Analytical results suggest that the free acids of the waxy coating of the apple have no influence on the incidence of superficial scald in cold-stored fruit. Treatment of fruit with various free and esterified acids had no marked influence on scald, which suggests that oxidation products of these acids are also unconnected with scald. A long-chain fatty aldehyde was found to be present in the wax. Two methods of scald prevention, wrapping in oiled paper and dipping in diphenylamine solution, were found to reduce the accumulation of this aldehyde in the waxy coating during storage. The evidence suggests that the scald-promoting factor is formed in the waxy coating of the fruit by an oxidative process during storage, rather than by direct natural synthesis.     

Particle Size Distribution of Natural Peanut Butter and Its Dynamic Rheological Properties

This study compared the dynamic rheological properties of natural peanut butter with commercial peanut butter at 25°C. The natural peanut butter was produced using ultra-high speed grinding (?20,000 rpm) at different grinding times (2–5 min) from peanuts of China and India. Multimodal particle size distribution was observed for all the samples. The linear viscoelastic region obtained from stress sweep test of the peanut butter produced at 2–3 min fell within the linear viscoelastic region of commercial peanut butter of 0.1–11 Pa. Longer grinding time (3.5–5 min) produced a shorter and lower linear viscoelastic region of 0.03–3 Pa. The storage modulus, G′ is an increasing function of particle size distribution. All peanut butter samples exhibited elastic properties.     

'Flavor-fade' and Off-Flavors in Ground Roasted Peanuts As Related to Selected Pyrazines and Aldehydes

Headspace volatiles from ground roasted Florunner medium peanuts, stored at 65°C for 1–68 days, were separated and identifled by GC/MS. Selected pyrazines, resulting from Maillard browning and selected aldehydes from autoxidation were evaluated to determine their mechanistic contributions to peanut ‘flavor-fade.’ The 2,6-dimethylpyrazine, 2-methylpyrazine, 2-ethyl-5-methyl or 6-methylpyrazine, 2,3,5-trimethylpyrazine, and pentanal remained constant during storage (p < 0.05). Flavor scores for ‘roasted peanut’ decreased slightly, then leveled off and hex-anal, heptanal, octanal and nonanal increased during storage (p < 0.05). Oxidative ‘rancid’ flavor scores and thiobarbituric acid values also increased during storage (p < 0.05). Based on results, the ‘flavor-fade’ of stored roasted peanuts is due to masking of pyrazines and other ‘roasted peanut’ flavor compounds by large quantities of low-molecular weight aldehydes from lipid autoxidation, and not due to polymerization and/or degradation of the pyrazines.     

花生荚果干燥技术及设备的研究现状与发展

花生作为世界重要的油料之一,在农作物中占据举足轻重的地位.刚收获的新鲜花生荚果由于水分较高易受到多种因素影响而导致霉变并产生黄曲霉毒素,从而影响使用安全并降低花生的经济价值.花生荚果收获后及时干燥可有效抑制微生物和霉菌的生长及繁殖,降低环境温湿度对花生储藏的影响,更大限度的保证花生的品质和使用安全.归纳了国内外花生荚果...     

Flavor and Oxidative Stability of Roasted High Oleic Acid Peanuts

A new peanut line has been developed at the University of Florida with about 80% oleic and 3% linoleic acid. Volatiles and sensory characteristics of roasted normal and high oleic acid peanuts stored at 25°C were compared. Volatiles were analyzed using adsorbent trapping and GCMS, a 20-member trained panel was used for sensory evaluation, and a GC sniffer port was used to evaluate odor characteristics of volatile isolates. Peroxide values were lower for high oleic (HO) peanuts than normal peanuts during storage at 25°C and 40°C. The hexanal content of the peanuts was higher for normal than HO. Peanutty flavor was more stable for HO than normal after 6 wk storage. Painty and cardboard flavors were higher in normal peanuts than HO during storage. Differences for both painty and cardboard flavors were significant after 6 wk storage. Pyrazines were more stable in HO peanuts. Shelf life was estimated from sensory data to be two times longer in HO peanuts.     

Protein-based coatings on peanut to minimise oil migration

Soy protein isolate (SPI) or calcium caseinate (CC)-based coatings were applied on peanuts as a barrier of oil migration, and their efficiency was evaluated. These coatings induced a decrease of oil migration as compared to the uncoated peanuts. Subsequently, three polysaccharides were individually added to the coating solution to prevent oil migration further. The incorporation of carboxymethylcellulose (CMC) with SPI and CC coating solutions significantly (p ? 0.05) decreased the migration of oil as compared to the coatings without CMC. The addition of pectin seemed unfavourable because it enhanced the migration of oil. Starch in SPI-based coating solution helped to decrease the oil migration, but it did not affect the migration level in samples treated with CC solution. The results from size-exclusion chromatography showed strong cross-links by glutaraldehyde and transglutaminase treatments in SPI and CC-based coating solutions. A strong cross-linking in protein-based coating correlated closely with a reduction in oil migration. For both proteins, the cross-linking by transglutaminase was most efficient for improving the effectiveness of coating. This study demonstrated that our protein-based coatings can be effectively implemented to food industry for better quality of peanut products.     

Functionality of Palm Oil as a Stabilizer in Peanut Butter

ABSTRACT: Studies have shown that palm oil is an effective stabilizer in peanut butter. The objective of our investigation was to better define the role of palm oil as a stabilizer. Peanut butters without and with palm oil added at concentrations of 1.5, 2.0, and 2.5% (w/w of peanuts), and Fix-X™ (hydrogenated rapeseed and cottonseed oils as commercial control) were stored at 0, 21, 30, and 45 °C for 23 wk. Palm oil improved the oil holding capacity (OHC) of peanut butters, but had no effect on their adhesiveness and hardness characteristics. The unstabilized and palm oil-stabilized peanut butters were not as good as the Fix-X™ stabilized peanut butters with regard to their OHC, hardness, and adhesiveness characteristics.