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.     

Effects of Sonication and Edible Coating Containing Rosemary and Tea Extracts on Reduction of Peanut Lipid Oxidative Rancidity

Rancidity due to the lipid oxidation process is a critical factor influencing the quality of roasted peanuts. Sonication in combination with edible coatings added with plant extracts may extend the oxidative stability of peanuts. Peanuts were roasted at 178°C for 15 min, subjected to sonication in hexane for 10 min, and then coated with carboxymethyl cellulose (CMC) solution mixed with rosemary, tea extracts, and α-tocopherol and stored at 35°C for 12 weeks. The oxidative stability of the samples was investigated by measuring the oxidative stability index. Reduction in oxidation of 66.1% and 10.4% was observed for samples roasted and coated with extracts of rosemary and tea, respectively, as compared to uncoated sample. However, the oxidative stability of samples roasted–sonicated and coated with extracts of rosemary and tea was improved by 100.7% and 28.1%, respectively, in relation to the control. Sonication beyond coating improved the oxidative stability of the samples mixed with rosemary, tea extracts, and α-tocopherol by 10.3%, 12.1%, 34.6%, and 17.7%, respectively. The L ^* , a ^* , and b ^* values indicated that the peanut coated with CMC mixed with rosemary, tea extracts, and tocopherol at different concentration levels did not have significant (P < 0.05) color change during the 12-week storage at 35°C.     

Ultrasonication and Edible Coating Effects on Lipid Oxidation of Roasted Peanuts

Lipid oxidation is an important factor affecting the quality of roasted peanuts. Coatings applied to the peanuts can enhance oxygen barriers to reduce rancidity. Ultrasonication was used to remove lipids from the peanuts prior to applying the coating to improve attachment of the coating on the peanut surface. Peanuts were roasted at 178°C for 15 min and then sonicated in hexane for 10 min. Whey protein isolate (WPI) 11%, corn protein (Zein) 15%, and carboxymethyl cellulose (CMC) 0.5% were used as coating materials. Sample treatments were: (1) roasted–coated with CMC (RCMC), WPI (RWPI), and Zein (RZEIN); (2) roasted–sonicated–coated with CMC (SCMC), WPI (SWPI), and Zein (SZEIN); (3) roasted–uncoated (R) as a control. Oxidative stability was investigated by gas chromatography–mass spectrometry (GC–MS) to detect formation of volatile compounds. The GC–MS indicated an eightfold, fivefold, and fourfold increase in hexanal formation in R, RZEIN, and SZEIN samples, respectively. But there was 80%, 91%, 18%, and 66% decrease in hexanal formation in RCMC, SCMC, RWPI, and SWPI samples, respectively, as compared to R. Sonication increased capability of coatings to delay hexanal formation by 11% and 48% for CMC and WPI, respectively, as compared to nonsonicated samples. Thus, the coating in combination with ultrasonication treatment was an effective method in delaying formation of oxidative volatile compounds and hence inhibiting rancidity of roasted peanuts.     

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.     

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.     

Improving the oxidative stability of sunflower seed kernels by edible biopolymeric coatings loaded with rosemary extract

An optimized combination of whey protein concentrate (WPC), glycerol and carboxymethyl cellulose (CMC) was determined by evaluating the mechanical properties of edible films and coating percentage on sunflower seed kernels (SUKs). The optimal coating solutions with/without rosemary extract (RAE) were used to improve oxidative stability of SUKs. Moreover, the efficiency of the coated SUKs was assessed in a sesame-based product, as a food system. The optimized composite coating (CMC 0.6% and WPC 8% by total solution weight, and glycerol 51% by WPC weight) provided the better color features for SUKs stored at elevated temperature compared to WPC coatings (10 and 11%, w/w) with a Maillard-induced red color, and it was more effective than CMC (4%, w/w) coating to improve the oxidative stability of the nuts. The RAE had a positive effect on the color characteristics of the composite and CMC coatings; however, it enhanced the oxidation of SUKs, which could be due to disruption of coating polymer network, and thus increasing the oxygen diffusion into the product. The food system containing the coated nuts exhibited a lower oxidation extent in comparison to the control formulation prepared by uncoated ones. Therefore, using an optimal composite coating, reddening of WPC at high temperatures and less oxidation protection efficiency of CMC were resolved as the kernels with desirable color and oxidative stability properties were produced, applicable in the formulation of products needing thermal processing.     

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.     

Whey Protein-Sucrose Coating Gloss and Integrity Stabilization by Crystallization Inhibitors

ABSTRACT: Whey protein coatings protect foods from change and deterioration and can extend product shelf life. However, because they are also made from food materials, whey protein coatings may also change over time if not properly formulated. Whey protein isolate (WPI)-sucrose high-gloss coatings, with and without crystallization inhibitors, were formed on chocolate-covered peanuts. The objective was to determine the effectiveness of crystallization inhibitors on preventing cracking of coatings and loss of coating gloss caused by sucrose crystallization during product storage. The 4 inhibitors tested were lactose, modified starch, polyvinylpyrrolidone, and raffinose. The WPI-coated chocolate-covered peanuts were stored for 119 d in 23%, 33%, and 44% relative humidity (RH) at 25°C. Gloss of the WPI coatings was measured periodically with a gloss-analysis system. It was found that raffinose is the most effective inhibitor of sucrose crystallization in whey protein-sucrose coatings. WPI coatings containing raffinose had significantly higher gloss values than all other coatings. For raffinose-containing samples stored in 23% and 33% RH environments, less than 3% of gloss was lost during storage. In 44% RH, the raffinose coating system had significantly less gloss fade than other WPI-sucrose coatings. This information can be used to improve the effectiveness of water-based high-gloss edible coatings.     

Whey Protein Coating Effect on The Oxygen Uptake of Dry Roasted Peanuts

A procedure was developed to coat peanuts with aqueous whey protein isolate (WPI) solutions based on increasing coating-solution viscosity. Oxygen uptake of WPI-coated nuts and uncoated nuts were compared. WPI coatings delayed oxygen uptake of dry roasted peanuts at intermediate (53%) and low (21%) storage relative humidity. They had similar results at 29°C and 37°C. The effects of coating thickness and storage relative humidity indicate that the mechanism of protection of the coatings was through their oxygen barrier properties.     

EFFICACY OF SOUR WHEY AS A SHELF‐LIFE ENHANCER: USE IN ANTIOXIDATIVE EDIBLE COATINGS OF BEEF STEAK*

ABSTRACT

Sour whey powder (SWP) based edible coatings, with and without carboxymethyl cellulose (CMC), were used to reduce oxidative degradation of cut beef steak stored at 2C for 5 days. Comparison was with calcium caseinate (CC) and soy protein isolate (SPI). Colorimetric measurements showed the mean of the color consistency index for L*, a*and b*scales of SWP to be highest with (18.3) and without CMC (19.8). Control gave a significantly lower value of 10.6. The percent inhibition of thiobarbituric acid reactive substances (TBARS) compared to control was 40.9, 38.9 and 48.9%, respectively for CC, SPI and SWP. In the same order, this value increased to 51.9, 45.1 and 59.2% when CMC was added to the coating. The peroxide value was also significantly reduced by SWP. Oxidative degradation as reflected by an increase in carbonyls and decrease in sulfhydryls was also reduced by SWP and it was better at this than the other proteins. Moisture barrier property of SWP based coating was the best and CMC significantly enhanced this property of CC and SPI though they did not fare well by themselves. Data show that SWP can effectively be used to extend quality and shelf life of beef steak.

PRACTICAL APPLICATIONS

In 2006, the U.S.A. produced more than 11.95 million metric tons of beef. Most of this was consumed as hamburger meat and steaks. Unfortunately, once the animal is slaughtered, meat undergoes oxidative degradation. Retail cut meats are particularly susceptible. Various antioxidative coatings have been tried with varying levels of success. The industry is keen for inexpensive and natural means. Recently, we successfully used sour whey, a byproduct of cottage cheese and/or caseinate manufacture, as natural antioxidative coating to extend shelf life of cut vegetables and apples. This part of our study investigates its efficacy in reducing oxidative degradation of retail cut beef steaks.     

Edible Film Coating to Minimize Eggshell Breakage and Reduce Post-Wash Bacterial Contamination Measured by Dye Penetration in Eggs

ABSTRACT: The mechanical and bacterial barrier properties of washed (tap water, sodium carbonate, Na₂CO₃, sodium hypochlorite, NaOCl) noncoated eggs and eggs coated with soy protein isolate (SPI), whey protein isolate (WPI), carboxylmethyl cellulose (CMC), or wheat gluten (WG) were evaluated. All coated eggshells showed greater puncture strength than those of noncoated eggs. The film-coated eggs reduced post-wash bacterial penetration as measured by dye penetration method. WPI coating completely inhibited blue dye penetration on average. These results suggest that WPI coatings can be used to reduce breakage of eggshell and egg microbial contamination.     

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.     

Milk Protein Coatings Prevent Oxidative Browning of Apples and Potatoes

ABSTRACT Color analysis on apple and potato slices coated with calcium caseinate or whey protein solutions showed that the 2 coatings efficiently delayed browning by acting as oxygen barriers. The antioxidant properties of the films were realized using a model allowing the release of oxidative species by electrolysis of saline buffer. Whey proteins were a better antioxidant capacity than calcium caseinate. Furthermore, addition of carboxymethyl cellulose (CMC) to the formulations significantly improved their antioxidative power. Best scavenging of oxygen free radicals and reactive oxygen species was found for films based on whey proteins and CMC which inhibited by 75% the formation of colored compounds produced by the reaction of the oxidative species with N,N‐diethyl‐p‐phenylenediamine.     

Study of Spray System Applications of Edible Coating Suspensions Based on Hydrocolloids Containing Cellulose Nanofibers on Grape Surface (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.)

An edible coating is a useful technology to preserve fruit quality by covering them with a protective layer which improves the appearance and provides a semipermeable barrier for gases and water vapor transfer, allowing extension of their shelf life. In this study, edible coatings based on hydroxypropyl methyl cellulose, k-carrageenan, glycerol, and cellulose nanofibers were formulated. The operational conditions of the spray system were studied to obtain a coating with optimal adhesion on grape (Vitis vinifera L.) surface. Furthermore, the physico-chemical properties of grapes covered with edible coatings were evaluated during refrigerated storage. A full factorial 2³ experimental design was applied, where liquid suspension flow (1–5 L h^?1), air pressure (50–200 kPa), and height of impact (0.3–0.5 m) were evaluated as independent variables, whereas the percentage of coating and thickness of coating was the response variables. Both mechanical and physico-chemical properties were evaluated during 41 days in both coated and uncoated grapes as shelf life criteria. Throughout the storage time, noticeable changes in pH and total soluble solids were not found in grapes covered with edible coatings and they showed the highest stability for the evaluated mechanical properties. Moreover, coated grapes showed final weight loss and water vapor permeability values of approximately 30 and 34% lower, respectively, than uncoated grapes, suggesting a shelf life extension.     

Peanut and Walnut Rancidity: Effects of Oxygen Concentration and Relative Humidity

Accelerated tests for oxidative rancidity of blanched peanuts, blanched dry-roasted peanuts, blanched oil-roasted peanuts and shelled Persian walnuts were performed at high and low oxygen content at controlled intermediate and low relative humidities. The results confirmed and quantified the importance of oxygen content, relative humidity and roasting process in the oxidative rancidity of peanuts and walnuts. There is a potential to extend shelf-life of roasted peanuts and walnuts by edible coatings with low oxygen permeability or nitrogen-flushing with oxygen barrier packaging. Static headspace chromatography was useful to monitor oxidative rancidity in walnuts and roasted peanuts.     

Whey protein isolate coating and concentration effects on egg shelf life

The influences of three different concentrations (6, 12 and 18%) of whey protein isolate (WPI) coatings on shelf‐life enhancements of the fresh egg quality (weight loss, pH, Haugh unit, yolk index and colors) and the shelf life were evaluated at room temperature. All coated eggs showed lower weight loss than uncoated eggs. Less weight loss (2.46 for 12% WPI and 2.38 for 18% WPI) was observed in WPI‐coated eggs. Haugh units (HU) indicated that coated eggs remained in grade ‘A’ during 3 weeks storage period, whereas uncoated (UC) changed from grade ‘A’ to ‘B’ after 1 week of storage. The HU and yolk‐index (YI) values of all WPI‐coated eggs were significantly higher than those of UC. Among the coated eggs, there were no significant differences in HU, but 12 and 18% WPI coated had higher YI than WPI 6% coated and UC. The albumen pH of the UC eggs was significantly higher than that of coated eggs. Yolk lightness (L*) and (b*); shell (a*) and (b*) of coated eggs were not different from UC after 4 weeks. Performance of WPI coatings depended on the concentration up to 12% but not between 12 and 18%. Results also indicated that WPI coatings served as protective barrier for shelf life of the eggs. Copyright © 2005 Society of Chemical Industry     

EFFECT OF CHOCOLATE COATING ON OXIDATIVE STABILITY OF NORMAL AND HIGH OLEIC PEANUTS

Oxidative stability studies were performed on roasted high-oleic acid peanuts (HOP-SunOleic 95) and normal oleic acid peanuts (NOP-Florunner). Peanuts were dry-roasted to a Hunter Lab value of approximately 50. Chocolate-coated peanut bars (6"x4"×1/2") were prepared using milk chocolate, white chocolate, and reduced-fat chocolate (containing salatrim). Chocolate bars were stored at 25C and 0.60 water activity (a_w). Uncoated peanuts were stored at 0.60 and 0.19 a_w at 25C. Samples were removed from storage at 4-week intervals for peroxide value measurement. Oxidation of peanuts with chocolate coatings were higher than the peanuts that were stored uncoated at the same a_w. The peroxide values of NOP were similar for chocolate coated treatments and 0.60 a_w control but the 0.19 a_w control was 2–4 times higher than the others. Chocolate-coated peanuts had higher oxidation rates compared to uncoated peanuts.     

Rehydration characteristics of freeze‐dried strawberry pieces as affected by whey protein edible coatings

This paper is about the use of whey protein isolate (WPI) edible coatings to improve the rehydration behaviour of freeze‐dried (FD) strawberry pieces. First, the optimal ratio sample mass/volume of coating solution was optimised by determining the rehydration ratio, bulk density and nutritional quality of the samples. Coating time is also determined in coated samples by light microscopy. Second, the effect of changing the pH and the variation in temperature–time to denaturate WPI on rehydration characteristics was also evaluated. The rehydration ratio of strawberry pieces decreased with increasing the denaturation temperature and denaturation time, while it increased with increasing pH of the coating solution. Third, according to the rehydration curves, coating was not a single layer but small pieces attached to strawberry pieces. The soluble protein contents in water after rehydration confirm this conclusion.     

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.