Influence of storage, heat treatment, and solids composition on the bleaching of whey with hydrogen peroxide

The residual annatto colorant in liquid whey is bleached to provide a desired neutral color in dried whey ingredients. This study evaluated the influence of starter culture, whey solids and composition, and spray drying on bleaching efficacy. Cheddar cheese whey with annatto was manufactured with starter culture or by addition of lactic acid and rennet. Pasteurized fat-separated whey was ultrafiltered (retentate) and spray dried to 34% whey protein concentrate (WPC34). Aliquots were bleached at 60 °C for 1 h (hydrogen peroxide, 250 ppm), before pasteurization, after pasteurization, after storage at 3 °C and after freezing at -20 °C. Aliquots of retentate were bleached analogously immediately and after storage at 3 or -20 °C. Freshly spray dried WPC34 was rehydrated to 9% (w/w) solids and bleached. In a final experiment, pasteurized fat-separated whey was ultrafiltered and spray dried to WPC34 and WPC80. The WPC34 and WPC80 retentates were diluted to 7 or 9% solids (w/w) and bleached at 50 °C for 1 h. Freshly spray-dried WPC34 and WPC80 were rehydrated to 9 or 12% solids and bleached. Bleaching efficacy was measured by extraction and quantification of norbixin. Each experiment was replicated 3 times. Starter culture, fat separation, or pasteurization did not impact bleaching efficacy (P > 0.05) while cold or frozen storage decreased bleaching efficacy (P < 0.05). Bleaching efficacy of 80% (w/w) protein liquid retentate was higher than liquid whey or 34% (w/w) protein liquid retentate (P < 0.05). Processing steps, particularly holding times and solids composition, influence bleaching efficacy of whey. PRACTICAL APPLICATION: Optimization of whey bleaching conditions is important to reduce the negative effects of bleaching on the flavor of dried whey ingredients. This study established that liquid storage and whey composition are critical processing points that influence bleaching efficacy.     

The effect of bleaching agents on the degradation of vitamins and carotenoids in spray-dried whey protein concentrate

Previous research has shown that bleaching affects flavor and functionality of whey proteins. The role of different bleaching agents on vitamin and carotenoid degradation is unknown. The objective of this study was to determine the effects of bleaching whey with traditional annatto (norbixin) by hydrogen peroxide (HP), benzoyl peroxide (BP), or native lactoperoxidase (LP) on vitamin and carotenoid degradation in spray-dried whey protein concentrate 80% protein (WPC80). An alternative colorant was also evaluated. Cheddar whey colored with annatto (15 mL/454 L of milk) was manufactured, pasteurized, and fat separated and then assigned to bleaching treatments of 250 mg/kg HP, 50 mg/kg BP, or 20 mg/kg HP (LP system) at 50°C for 1 h. In addition to a control (whey with norbixin, whey from cheese milk with an alternative colorant (AltC) was evaluated. The control and AltC wheys were also heated to 50°C for 1 h. Wheys were concentrated to 80% protein by ultrafiltration and spray dried. The experiment was replicated in triplicate. Samples were taken after initial milk pasteurization, initial whey formation, after fat separation, after whey pasteurization, after bleaching, and after spray drying for vitamin and carotenoid analyses. Concentrations of retinol, a-tocopherol, water-soluble vitamins, norbixin, and other carotenoids were determined by HPLC, and volatile compounds were measured by gas chromatography-mass spectrometry. Sensory attributes of the rehydrated WPC80 were documented by a trained panel. After chemical or enzymatic bleaching, WPC80 displayed 7.0 to 33.3% reductions in retinol, β-carotene, ascorbic acid, thiamin, α-carotene, and α-tocopherol. The WPC80 bleached with BP contained significantly less of these compounds than the HP- or LP-bleached WPC80. Riboflavin, pantothenic acid, pyridoxine, nicotinic acid, and cobalamin concentrations in fluid whey were not affected by bleaching. Fat-soluble vitamins were reduced in all wheys by more than 90% following curd formation and fat separation. With the exception of cobalamin and ascorbic acid, water-soluble vitamins were reduced by less than 20% throughout processing. Norbixin destruction, volatile compound, and sensory results were consistent with previous studies on bleached WPC80. The WPC80 colored with AltC had a similar sensory profile, volatile compound profile, and vitamin concentration as the control WPC80.     

The effect of starter culture and annatto on the flavor and functionality of whey protein concentrate

The flavor of whey protein can carry over into ingredient applications and negatively influence consumer acceptance. Understanding sources of flavors in whey protein is crucial to minimize flavor. The objective of this study was to evaluate the effect of annatto color and starter culture on the flavor and functionality of whey protein concentrate (WPC). Cheddar cheese whey with and without annatto (15 mL of annatto/454 kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a mesophilic lactic starter culture or by addition of lactic acid and rennet (rennet set). Pasteurized fat-separated whey was then ultrafiltered and spray dried into WPC. The experiment was replicated 4 times. Flavor of liquid wheys and WPC were evaluated by sensory and instrumental volatile analyses. In addition to flavor evaluations on WPC, color analysis (Hunter Lab and norbixin extraction) and functionality tests (solubility and heat stability) also were performed. Both main effects (annatto, starter) and interactions were investigated. No differences in sensory properties or functionality were observed among WPC. Lipid oxidation compounds were higher in WPC manufactured from whey with starter culture compared with WPC from rennet-set whey. The WPC with annatto had higher concentrations of p-xylene, diacetyl, pentanal, and decanal compared with WPC without annatto. Interactions were observed between starter and annatto for hexanal, suggesting that annatto may have an antioxidant effect when present in whey made with starter culture. Results suggest that annatto has a no effect on whey protein flavor, but that the starter culture has a large influence on the oxidative stability of whey.     

Effect of bleaching whey on sensory and functional properties of 80% whey protein concentrate

Whey is a highly functional food that has found widespread use in a variety of food and beverage applications. A large amount of the whey proteins produced in the United States is derived from annatto-colored Cheddar cheese. Color from annatto is undesirable in whey and must be bleached. The objective of this study was to compare 2 commercially approved bleaching agents, benzoyl peroxide (BP) and hydrogen peroxide (HP), and their effects on the flavor and functionality of 80% whey protein concentrate (WPC80). Colored and uncolored liquid wheys were bleached with BP or HP, and then ultrafiltered, diafiltered, and spray-dried; WPC80 from unbleached colored and uncolored Cheddar whey were manufactured as controls. All treatments were manufactured in triplicate. The WPC80 were then assessed by sensory, instrumental, functionality, color, and proximate analysis techniques. The HP-bleached WPC80 were higher in lipid oxidation compounds (specifically hexanal, heptanal, octanal, nonanal, decanal, dimethyl disulfide, and 1-octen-3-one) and had higher fatty and cardboard flavors compared with the other unbleached and BP-bleached WPC80. The WPC80 bleached with BP had lower norbixin concentrations compared with WPC80 bleached with HP. The WPC powders differed in Hunter color values (L, a, b), with bleached powders being more white, less red, and less yellow than unbleached powders. Bleaching with BP under the conditions used in this study resulted in larger reductions in yellowness of the powders made from whey with annatto color than did bleaching with HP. Functionality testing demonstrated that whey bleached with HP treatments had more soluble protein after 10 min of heating at 90°C at pH 4.6 and pH 7 than the no-bleach and BP treatments, regardless of additional color. Overall, HP bleaching caused more lipid oxidation products and subsequent off-flavors compared with BP bleaching. However, heat stability of WPC80 was enhanced by HP bleaching compared with control or BP-bleached WPC80.     

Enzymatic bleaching in commercial colored Cheddar whey retentates

The effect of enzymatic bleaching with lactoperoxidase (LP) or exogenous peroxidase (EP) on the color and flavor of commercially produced whey protein concentrates (34% or 80% protein on a dry weight basis) was evaluated. Optimum levels of added H₂O₂ and optimum bleaching times were determined in commercial retentates by quantifying norbixin destruction. Retentates were then bleached and sensory and volatile analyses were conducted. In some retentates, LP-induced bleaching was not observed; however, EP-induced bleaching was effective under all conditions. Enzymatically-induced bleaching (both LP and EP) occurred faster at 35 °C than at 4 °C. Solids level also affected the speed of bleaching; samples with lower solids bleached in less time than those with higher solids. Bleached retentates, regardless of treatment, were higher in aroma intensity and cardboard flavor and were also higher in aldehydes. LP activity and subsequent bleaching of commercial retentates was variable while EP-induced bleaching was consistently effective.     

Effect of temperature and bleaching agent on bleaching of liquid Cheddar whey

The use of whey protein as an ingredient in foods and beverages is increasing, and thus demand for colorless and mild-tasting whey protein is rising. Bleaching is commonly applied to fluid colored cheese whey to decrease color, and different temperatures and bleach concentrations are used. The objectives of this study were to compare the effects of hot and cold bleaching, the point of bleaching (before or after fat separation), and bleaching agent on bleaching efficacy and volatile components of liquid colored and uncolored Cheddar whey. First, Cheddar whey was manufactured, pasteurized, fat-separated, and subjected to one of a number of hot (68°C) or cold (4°C) bleaching applications [hydrogen peroxide (HP) 50 to 500 mg/kg; benzoyl peroxide (BP) 25 to 100 mg/kg] followed by measurement of residual norbixin and color by reflectance. Bleaching agent concentrations were then selected for the second trial. Liquid colored Cheddar whey was manufactured in triplicate and pasteurized. Part of the whey was collected (no separation, NSE) and the rest was subjected to fat separation (FSE). The NSE and FSE wheys were then subdivided and bleaching treatments (BP 50 or 100 mg/kg and HP 250 or 500 mg/kg) at 68°C for 30 min or 4°C for 16 h were applied. Control NSE and FSE with no added bleach were also subjected to each time-temperature combination. Volatile compounds from wheys were evaluated by gas chromatography-mass spectrometry, and norbixin (annatto) was extracted and quantified to compare bleaching efficacy. Proximate analysis, including total solids, protein, and fat contents, was also conducted. Liquid whey subjected to hot bleaching at both concentrations of HP or at 100mg/kg BP had greater lipid oxidation products (aldehydes) compared with unbleached wheys, 50mg/kg BP hot-bleached whey, or cold-bleached wheys. No effect was detected between NSE and FSE liquid Cheddar whey on the relative abundance of volatile lipid oxidation products. Wheys bleached with BP had lower norbixin content compared with wheys bleached with HP. Bleaching efficacy of HP was decreased at 4°C compared with 68°C, whereas that of BP was not affected by temperature. These results suggest that fat separation of liquid Cheddar whey has no effect on bleaching efficacy or lipid oxidation and that hot bleaching may result in increased lipid oxidation in fluid whey.     

Survey of usage and estimated intakes of annatto extracts

In 2002, the Joint FAO/WHO Expert Committee on Food Additives requested information relating to the toxicity, intake and specifications of annatto. Previous intake estimates for annatto provided ambiguous results because the bixin/norbixin content of annatto extract was unclear. European annatto producers consulted with the food industry to determine use levels of specific annatto extracts. These data were combined with the levels of bixin/norbixin in particular extracts to estimate the concentration of bixin/norbixin in foods. Concentrations in food were combined with data about food consumption using various methods to estimate consumer intakes, which ranged from less than 1–163% of the acceptable daily intake (0.065 mg/kg bw/day). Higher intake estimates are conservative because they assume that a consumer always chooses a food that is coloured with annatto extracts. In practice this is extremely unlikely, since annatto is associated only with certain product/flavour combinations.     

Characterizing endogenous and exogenous peroxidase activity for bleaching of fluid whey and retentate

The lactoperoxidase (LP) system may be used to achieve the desired bleaching of fluid whey with the addition of low concentrations (<50 mg/kg) of hydrogen peroxide. The addition of an exogenous peroxidase (EP) to whey may also be used to aid in whey bleaching when the LP system is not fully active. The objectives of this study were to monitor LP activity in previously refrigerated or frozen milk, fluid whey, and whey retentate (10% solids) and to evaluate peroxidase activity in fluid whey and whey retentate (10% solids), with and without additional EP (2, 1, or 0.5 dairy bleaching units), over a range of pH (5.5–6.5) and temperatures (4–60°C). Subsequent experiments were conducted to determine the relationship between enzyme activity and bleaching efficacy. Raw and pasteurized milk, fat-separated pasteurized whey, and whey retentate (10% solids) were evaluated for LP activity following storage at 4 or −20°C, using an established colorimetric method. A response surface model was applied to evaluate both endogenous and EP activity at various temperatures and pH in freshly manufactured whey and retentate. Refrigerated or frozen storage at the parameters evaluated did not affect LP activity in milk, whey, or retentate. In fluid whey, with and without added EP, as pH decreased (to 5.5) and temperature increased (to 60°C), peroxidase activity increased. Retentate with EP exhibited behavior similar to that of fluid whey: as pH decreased and temperature increased, activity increased. However, in retentate without EP, as pH increased and temperature increased, activity increased. Enzyme activity was negatively correlated to bleaching time (time for >80% norbixin destruction) in fluid whey but a linear relationship was not evident in retentate. When fluid whey is bleached enzymatically, if pH is decreased and temperature is increased, the rate of reaction increases (e.g., bleaching occurs in less time). When bleaching in retentate, a higher pH (pH 6.5 vs. pH 5.5) is desired for optimal bleaching by the LP system. Due to processing restraints, this may not be possible for all dairy producers to achieve and, thus, addition of EP could be beneficial to improve bleaching efficacy.     

Effect of light,pH, metal ions and antioxidants on the colour stability of norbixin in aqueous solution

Norbixin, a carotenoid extracted from the seeds of the annatto (Bixa orellana) plant, can be used in aqueous food applications, where other carotenoids are too hydrophobic to solubilise in a water environment. The aim of this work was to investigate the effect of pH, antioxidants and transition metal ions with and without hydrogen peroxide (H₂O₂) on the stability of norbixin in aqueous solutions as well as determining the interaction between these factors and light. The stability of norbixin in buffered aqueous solution stored in light or in the dark was evaluated using absorbance spectrophotometry. Light, reduced pH and metal ions both with and without H₂O₂ increased the bleaching of norbixin, whereas chelators and the natural antioxidants, ascorbic acid and tocopherol, reduced the bleaching of norbixin. Light significantly increased the loss of norbixin alone and in combination with the other factors.     

Sanitizer treatments alleviate lignification of sliced few-flower wildrice (Zizania latifolia Turcz.)

To investigate the effects of sanitation processing on the lignification of few-flower wildrice (FFW), fresh-cut FFW was treated with water (control), 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂, packed in polyethylene film bags and stored at 2 °C for 21 days. Firmness, lignin, cellulose, hemicellulose and lignin forming related enzymes activities were examined. Sanitizer treatments inhibited the increases of firmness, lignin and cellulose than the control. The changes of hemicelluloses did not show a difference between the control and PAA treatment. An increase in the activities of phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), and a reduction in catalase (CAT) and superoxide dismutase (SOD) activities, were detected in the sliced FFW in the incompatible interaction. Compared with the control, sanitizers suppressed the activities of PAL, POD and PPO, but enhanced the activities of SOD and CAT during 21 days of storage. These enzymatic activities varied with different sanitizers. These results show that 80 mg/L peroxyacetic acid (PAA), 100 mg/L ClO₂ or 50 mg/L H₂O₂ sanitation processing can maintain tenderness, alleviate the lignification and fibrosis of fresh-cut FFW.     

The effect of bleaching agent on the flavor of liquid whey and whey protein concentrate

The increasing use and demand for whey protein as an ingredient requires a bland-tasting, neutral-colored final product. The bleaching of colored Cheddar whey is necessary to achieve this goal. Currently, hydrogen peroxide (HP) and benzoyl peroxide (BPO) are utilized for bleaching liquid whey before spray drying. There is no current information on the effect of the bleaching process on the flavor of spray-dried whey protein concentrate (WPC). The objective of this study was to characterize the effect of bleaching on the flavor of liquid and spray-dried Cheddar whey. Cheddar cheeses colored with water-soluble annatto were manufactured in duplicate. Four bleaching treatments (HP, 250 and 500 mg/kg and BPO, 10 and 20 mg/kg) were applied to liquid whey for 1.5 h at 60°C followed by cooling to 5°C. A control whey with no bleach was also evaluated. Flavor of the liquid wheys was evaluated by sensory and instrumental volatile analysis. One HP treatment and one BPO treatment were subsequently selected and incorporated into liquid whey along with an unbleached control that was processed into spray-dried WPC. These trials were conducted in triplicate. The WPC were evaluated by sensory and instrumental analyses as well as color and proximate analyses. The HP-bleached liquid whey and WPC contained higher concentrations of oxidation reaction products, including the compounds heptanal, hexanal, octanal, and nonanal, compared with unbleached or BPO-bleached liquid whey or WPC. The HP products were higher in overall oxidation products compared with BPO samples. The HP liquid whey and WPC were higher in fatty and cardboard flavors compared with the control or BPO samples. Hunter CIE Lab color values (L*, a*, b*) of WPC powders were distinct on all 3 color scale parameters, with HP-bleached WPC having the highest L* values. Hydrogen peroxide resulted in a whiter WPC and higher off-flavor intensities; however, there was no difference in norbixin recovery between HP and BPO. These results indicate that the bleaching of liquid whey may affect the flavor of WPC and that the type of bleaching agent used may affect WPC flavor.     

Short communication: Norbixin and bixin partitioning in Cheddar cheese and whey

The Cheddar cheese colorant annatto is present in whey and must be removed by bleaching. Chemical bleaching negatively affects the flavor of dried whey ingredients, which has established a need for a better understanding of the primary colorant in annatto, norbixin, along with cheese color alternatives. The objective of this study was to determine norbixin partitioning in cheese and whey from full-fat and fat-free Cheddar cheese and to determine the viability of bixin, the nonpolar form of norbixin, as an alternative Cheddar cheese colorant. Full-fat and fat-free Cheddar cheeses and wheys were manufactured from colored pasteurized milk. Three norbixin (4% wt/vol) levels (7.5, 15, and 30 mL of annatto/454 kg of milk) were used for full-fat Cheddar cheese manufacture, and 1 norbixin level was evaluated in fat-free Cheddar cheese (15 mL of annatto/454 kg of milk). For bixin incorporation, pasteurized whole milk was cooled to 55°C, and then 60 mL of bixin/454 kg of milk (3.8% wt/vol bixin) was added and the milk homogenized (single stage, 8 MPa). Milk with no colorant and milk with norbixin at 15 mL/454 kg of milk were processed analogously as controls. No difference was found between the norbixin partition levels of full-fat and fat-free cheese and whey (cheese mean: 79%, whey: 11.2%). In contrast to norbixin recovery (9.3% in whey, 80% in cheese), 1.3% of added bixin to cheese milk was recovered in the homogenized, unseparated cheese whey, concurrent with higher recoveries of bixin in cheese (94.5%). These results indicate that fat content has no effect on norbixin binding or entrapment in Cheddar cheese and that bixin may be a viable alternative colorant to norbixin in the dairy industry.     

Short communication: Sensitive detection of norbixin in dried dairy ingredients at concentrations of less than 1 part per billion

Norbixin is the water-soluble carotenoid in annatto extracts used in the cheese industry to color Cheddar cheese. The purpose of norbixin is to provide cheese color, but norbixin is also present in the whey stream and contaminates dried dairy ingredients. Regulatory restrictions dictate that norbixin cannot be present in dairy ingredients destined for infant formula or ingredients entering different international markets. Thus, there is a need for the detection and quantification of norbixin at very low levels in dried dairy ingredients to confirm its absence. A rapid method for norbixin evaluation exists, but it does not have the sensitivity required to confirm norbixin absence at very low levels in compliance with existing regulations. The current method has a limit of detection of 2.7 μg/kg and a limit of quantification of 3.5 μg/kg. The purpose of this study was to develop a method to extract and concentrate norbixin for quantification in dried dairy ingredients below 1 μg/kg (1 ppb). A reverse-phase solid-phase extraction column step was applied in the new method to concentrate and quantify norbixin from liquid and dried WPC80 (whey protein concentrate with 80% protein), WPC34 (WPC, 34% protein), permeate, and lactose. Samples were evaluated by both methods for comparison. The established method was able to quantify norbixin in whey proteins and permeates (9.39 μg/kg to 2.35 mg/kg) but was unable to detect norbixin in suspect powdered lactose samples. The newly developed method had similar performance to the established method for whey proteins and permeates but was also able to detect norbixin in powdered lactose samples. The proposed method had a >90% recovery in lactose samples and a limit of detection of 28 ppt (ng/kg) and a limit of quantification of 94 ppt (ng/kg). The developed method provides detection and quantification of norbixin for dairy ingredients that have a concentration of <1 ppb.     

Formation of soluble protein complexes and yoghurt properties influenced by the addition of whey protein concentrate

The effects of whey protein concentrate (WPC) on the formation of soluble protein complexes and yoghurt texture were evaluated. Skim milk (SM) and skim milk enriched with 1% WPC (SM + 1%WPC) or 2% WPC (SM + 2%WPC) were left unheated or heated and then made into yoghurt gels. Yoghurt prepared from heated SM + 2%WPC had significantly higher storage modulus, water holding capacity and firmness values and a denser microstructure than those prepared only from skim milk. Electrophoretic analysis of the milk showed that the level of β-lactoglobulin and κ-casein in the serum phase increased with increasing WPC concentration, indicating that the content of disulfide-linked β-lactoglobulin and κ-casein was higher in SM + 2%WPC than in SM, suggesting that more soluble protein complexes had been formed. Consequently, yoghurt prepared from heated SM enriched with WPC may have more bonds and more protein complexes in the protein network than yoghurt prepared only from SM, thus resulting in firmer gels.Practical applicationsYoghurt, one of the most popular fermented milk products, is of high economic importance to the dairy industry worldwide. In particular, high-protein yoghurt, such as Greek-style or set-type yoghurt, has been driving its ongoing popularity over recent years. In current industrial production of high-protein yoghurt, protein fortification and heat treatment of milk are two of the most important processing parameters affecting yoghurt texture. Whey protein concentrate has been added to milk to reduce whey separation and to increase the firmness of the yoghurt. From a technological point of view, the interaction of the denatured whey proteins with casein micelles or with κ-casein in the serum phases is regarded as responsible for obtaining a good yoghurt structure. The present research has shown that it is possible to produce yoghurt with a range of textural properties by precisely controlling the rate of whey protein fortification during its manufacture. Therefore, this study provides a better understanding of the effect of WPC fortification and aims to extend this insight for the production of good-quality yoghurt.     

Concentration of Milk and Whey Using Composite,Spiral Wound,Reverse Osmosis Membranes

Two types of spiral wound, composite, reverse osmosis membranes, referred to as Phase I and Phase II, were studied in the concentration of milk and whey. The membranes can tolerate a pH range of 2 to 13, 50 ppm available Cl, 100 ppm H₂O₂, and temperatures up to 52°C.Two phase II membranes, Part A and Part B, sanitized using 50 ppm available Cl and 100 ppm H₂O₂, respectively, had average water fluxes of 71 an 69 L/m²h, respectively, at standard operating conditions. Phase II, Part A and Part B membranes had average NaCl rejections of 96.7 and 97.8%, respectively. Phase I modules had significantly lower permeate fluxes and salt rejections and significantly higher flux decline parameters than the Phase II membranes.The Phase II, Part B membranes had average permeate fluxes at a concentration factor of 2 for sweet whey, acid whey, and skim milk of 29, 36, and 14 L/m²h at standard operating conditions. The Phase II, Part B membranes had significantly higher average permeate fluxes than Phase II, Part A and Phase I membranes.Phase II membranes exhibited comparable or better performance than cellulose acetate membranes and can be used more easily in the dairy industry.     

Degradation of various fruit juice anthocyanins by hydrogen peroxide

Degradation kinetics of anthocyanins was studied in sour cherry nectar, pomegranate and strawberry juices at high hydrogen peroxide (H₂O₂) concentrations (9.31–27.92 mmol l⁻¹) at 10–30 °C and in only sour cherry nectar at low H₂O₂ concentrations (0.23–2.33 mmol l⁻¹) at 20 °C. Degradation of anthocyanins followed the first-order reaction kinetics. Sour cherry anthocyanins were the most resistant to H₂O₂, followed by pomegranate and strawberry anthocyanins. Degradation of anthocyanins was also studied in sour cherry nectar and pomegranate juice in the presence of ascorbic acid at 60 and 80 mg l⁻¹ concentrations at 20 °C. At 80 mg level, ascorbic acid significantly accelerated the degradation of anthocyanins in sour cherry nectar at 4.65, 6.98 and 9.31 mmol l⁻¹ H₂O₂ concentrations. In contrast, ascorbic acid at both 60 and 80 mg levels protected the anthocyanins from degradation by H₂O₂ in pomegranate juice.     

The Influence of Bleaching Agent and Temperature on Bleaching Efficacy and Volatile Components of Fluid Whey and Whey Retentate

Fluid whey or retentate are often bleached to remove residual annatto Cheddar cheese colorant, and this process causes off‐flavors in dried whey proteins. This study determined the impact of temperature and bleaching agent on bleaching efficacy and volatile components in fluid whey and fluid whey retentate. Freshly manufactured liquid whey (6.7% solids) or concentrated whey protein (retentate) (12% solids, 80% protein) were bleached using benzoyl peroxide (BP) at 100 mg/kg (w/w) or hydrogen peroxide (HP) at 250 mg/kg (w/w) at 5 °C for 16 h or 50 °CC for 1 h. Unbleached controls were subjected to a similar temperature profile. The experiment was replicated three times. Annatto destruction (bleaching efficacy) among treatments was compared, and volatile compounds were extracted and separated using solid phase microextraction gas chromatography mass spectrometry (SPME GC‐MS). Bleaching efficacy of BP was higher than HP (P < 0.05) for fluid whey at both 5 and 50 °C. HP bleaching efficacy was increased in retentate compared to liquid whey (P < 0.05). In whey retentate, there was no difference between bleaching with HP or BP at 50 or 5 °C (P > 0.05). Retentate bleached with HP at either temperature had higher relative abundances of pentanal, hexanal, heptanal, and octanal than BP bleached retentate (P < 0.05). Liquid wheys generally had lower concentrations of selected volatiles compared to retentates. These results suggest that the highest bleaching efficacy (within the parameters evaluated) in liquid whey is achieved using BP at 5 or 50 °C and at 50 °C with HP or BP in whey protein retentate.