Stability of Concentrated,Decolorized, Deionized Hydrolyzed Whey Permeate

Four separate lots of whey permeate from ultrafiltration of sweet cheese whey were deionized and decolorized to remove whey-like flavor and color, treated with β-galactosidase to hydrolyze lactose, and concentrated. Variables introduced were levels of lactose hydrolysis and total solids; storage temperature; order of deionization, hydrolysis, and decolorization processes; and use of a 75°C posthydrolysis heat treatment. Each batch was evaluated for microbial stability, resistance to crystallization, and flavor after 3 mo storage at 37°C.Concentration of permeate to less than 60% total solids resulted in microbial instability, and greater than 85% lactose hydrolysis resulted in galactose or lactose crystallization. Heating to 75°C and storing at elevated temperatures (up to 37°C) minimized crystallization. However, heating to 75°C accelerated browning. Flavor evaluation of browned samples suggested that caramelization rather than Maillard browning was the principal factor. Decolorizing with activated carbon after hydrolysis made no difference to the amount of sugar crystallization.Lactose hydrolysis improved the stability of concentrated, decolorized, deionized hydrolyzed whey permeate. The syrup with longest storage stability was decolorized, 90% deionized, contained 85 to 90% hydrolyzed lactose, was concentrated to 65% total solids, heated to 75°C following concentration, and stored at 30°C.     

Conversion of glucose in lactase-hydrolyzed whey permeate to fructose with immobilized glucose isomerase

The maximum conversion of glucose to fructose in lactase-hydrolyzed whey permeate by glucose isomerase was approximately 52% at .1 g enzyme/ml substrate after 7 h incubation at 60 degrees C. Removal of minerals from the substrate was essential for enzyme activity. The dependence of the enzyme on Mg++ and Co++ for activity in the presence of high ash concentration was demonstrated. Optimum Mg++ and Co++ additions were 250 and 100 ppm, respectively. The isomerization reaction was enhanced more when both 100 ppm Mg++ and 50 ppm Co++ were added. Hydrolyzed isomerized lactose whey syrup with sweetness equivalent to sucrose was successfully produced through enzymatic isomerization of glucose in lactase-hydrolyzed whey permeate after supplementation with pure glucose. Fructose in hydrolyzed isomerized lactose whey syrup was effectively separated from other sugars by Dowex 1X8-200 anion exchange resin in the bisulfite form.     

Process for calcium retention during skim milk ultrafiltration

Lactose is separated from milk or other fluid dairy products for a variety of reasons. Ultrafiltration is a known process of removing lactose from these products. However, during ultrafiltration, valuable minerals, such as calcium in soluble form, are also lost into permeate. In this study, a process was developed in which first the lactose reduction in skim milk was achieved by ultrafiltration (4x volumetric concentration) using a 10-kDa membrane. Then, the calcium present in permeate was precipitated using one of three methods: 1) heat treatment, 2) pH adjustment, or 3) a combination of pH adjustment and heat treatment to permeate, then recovered by refiltering permeate. The process was first developed at laboratory scale, and then its applicability was tested at the pilot scale. Skim milk, retentates, permeates, and the treated permeates were analyzed for total solids, ash, protein, or total nitrogen, calcium, and lactose content. About 76% of the total lactose and about 16% of the calcium present in skim milk permeated through the membrane during ultrafiltration. The three treatments applied produced white precipitates and turned the clear permeates turbid. On refiltering the treated permeates approximately 42, approximately 50, and approximately 70% of the total calcium present could be recovered from 1) heat-treated, 2) pH-adjusted, and 3) pH-adjusted and heat-treated permeates, respectively. There was no marked change in the lactose content due to any of the three treatments and subsequent refiltering of the treated permeates.     

Lactose hydrolysis in acid whey with subsequent glucose isomerisation

The disposal of whey is a problem because of its high biological oxygen demand. Of the 1.8 × 10¹⁰ kg produced annually in the USA, only about half has any food or feed application (Jelen 1983). One possible approach to acid whey utilisation is the removal of the proteins either by ultrafiltration or by thermal precipitation, hydrolysis of lactose with soluble β-galactosidase (lactase, EC 3.2.1.23) and subsequent isomerisation of the glucose to fructose by the action of immobilised glucose isomerase (EC 5.3.1.5). The resulting syrup is composed of glucose, fructose and galactose plus small amounts of unhydrolysed lactose and other oligosaccharides. The syrup was found to have a predominantly sweet and slightly salty taste. Recently sucrose has been replaced in many foods by high fructose corn syrup produced by the action of glucose isomerase on glucose syrups from corn starch hydrolysates (Bucke 1981). The whey syrup also has potential as a sucrose substitute.     

Utilization of Cheese Whey Permeate in Canned Beans and Plums

Navy and kidney beans (Phaseolus vulgaris) were hydrated in water, then canned in brines designated as control, whey permeate (WP), and hydrolyzed lactose whey permeate (HP). Hunter Lab Color Difference and Kramer Shear texture analyses indicated general darkening and increased firmness in permeate treated beans. Total solids and ash increased significantly in the treated samples. There was a significantly lower preference for beans treated with permeate fractions than for control beans. Plums were canned in a control sucrose syrup (20° Brix) and in syrups with 5, 10, 15, 20, and 25% replacement of sucrose with HP, or crystalline glucose-galactose (GG) mixture. HP plums were generally darker in color and similar in texture to the control samples. Sensory tests showed that general acceptability of HP plums was similar to control samples.     

Determination of Lactose and Sucrose Contents of Ice Cream Mix via Enzymatic-Cryoscopic Methodology

A simple method was developed for determining the lactose and sucrose contents of ice cream mix. The method is based on measuring the freezing point depression resulting from incubating samples with invertase (EC 3.2.1.26) and β-galactosidase (EC 3.2.1.23). Sucrose and lactose concentrations are determined separately with each determination requiring 50 units of enzyme and 2 hr of incubation at 37°C. A standard curve for lactose determination was obtained using ice cream mixes containing various amounts of sucrose and corn syrup solids (R²= 0.996, C.V. = 1.2%). A standard curve for sucrose determination was obtained using ice cream mixes containing various amounts of lactose and corn syrup solids (R²= 0.996, C.V. = 1.9%).     

Lactose Hydrolysis in Ultrafiltration-Treated Cottage Cheese Whey with Various Whey Protein Concentrations

Lactose hydrolysis by soluble Aspergillus oryzaeβ-galactosidase was studied in (a) ultrafiltration (UF) permeate containing varying concentrations of isolated β-lactoglobulin or serum albumin; (b) UF retentate at four protein levels; and (c) cottage cheese whey during the UF treatment in an Amicon stirred cell unit. The rate and extent of lactose hydrolysis achieved in all the conditions studied was independent of protein concentration in the whey preparations used. After 6 hr of the simultaneous UF-lactose hydrolysis process at room temperature, similar hydrolysis level was achieved in the retentate as in the batch hydrolysis process. The average degree of hydrolysis in the permeate was 52.6%. The retentate added to milk at room temperature hydrolysed 93% of the lactose in 15 hr.     

Studies on the Combined Action of Amylases and Glucose Isomerase on Starch and its Hydrolysates. Part III. Conversion of Starch to Glucose-Fructose Syrup

Glucose syrup was produced by liquefaction of starch using acid, acid-enzyme, one-step enzyme and two-steps enzyme process followed by saccharification by free and immobilized glucoamylase. The effect of D-glucose concentration and temperature on conversion of glucose syrup by glucose isomerase was studied. 50% glucose concentration and temperature range of 65 – 70°C gave the maximum conversion value to fructose. The isomerization was applied as a pilot plant process. The relative sweetness of glucose-fructose syrup was calculated and found that the syrup with fructose content of 26% has the same sweetness as sucrose.     

Stability of Proteins in Ultrafiltered, Low-Lactose Milk Concentrate During Frozen Storage

Cascin in concentrated milk (3×) destabilizes after 1–3 wk at –8°C. USC of an ultrafiltration (UF) process to partially remove lactose from milk, followed by replacement of all or part of the removed lactose with corn syrup, glucose or sucrose can greatly extend protein stability. Protein stability improves as the amount of nonlactose carbohydrate is increased and the amount of lactose is decreased. Although nutritionally significant amounts of minerals and vitamins arc removed by this process, they can be easily replaced. Samples of skim and whole milk from which 68–72% of the lactose is removed by UI: and replaced on an equal weight basis with corn syrup are stable for more than 34 wk at –8°C.     

Short communication: utilization of sheep's milk cheese whey in the manufacture of an alkylphenol flavor concentrate

The recovery of species-related conjugated sheep-like flavored alkylphenols from Manchego-type cheese whey by ultrafiltration was investigated. Concentrations of conjugated alkylphenols were similar in the various fractions of whey permeate collected during ultrafiltration, and this was interpreted as a reflection of their high water solubility. About 49 and 62% of conjugated 3- and 4-ethylphenols and p- and m-cresols in sheep's milk cheese whey, respectively, were recovered in the permeate after ultrafiltration with a volume concentration factor of 5.4. Cheese whey retentate correspondingly contained 38 and 28% of conjugated 3- and 4-ethylphenols and p- and m-cresols from the original whey, respectively. Permeate fractions from sheep's milk cheese whey were combined, concentrated by vacuum evaporation, and lactose was partially removed by crystallization and filtration to obtain an aqueous sheep-like flavor precursor concentrate.     

Flavor Losses in Orange Juice during Ultrafiltration and Subsequent Evaporation

Losses of volatile compounds in orange juice during ultrafiltration and subsequent evaporation were studied. Alcohols and esters predominated in the permeate, while terpenes (d-limonene and valencene) and nonpolar aldehydes (octanal and decanal) were distributed in the retentate from the ultrafiltration (UF) system. Fractions of some flavor compounds were lost during ultrafiltration process. An aqueous phase essence was recovered from the permeate during evaporative concentration. No oil phase was observed. When whole juice was concentrated, both oil and aqueous phases were recovered. Essence recovery efficiency of individual compounds was 3 to 13% when concentrating permeate and <5% when concentrating whole juice.     

Separation of non-sucrose compounds from syrup as a part of the sugar-beet production process by ultrafiltration with ceramic membranes

Non-sucrose compounds having intensive colour tend to build into the sucrose crystals during the crystallization. Their removal, or decrease of their concentration in sugar syrup, is a very important operation. The subject of this laboratory investigation was a separation process performed by ceramic tubular membrane in two modes of operation: with static mixer (SM) and without static mixer (NSM). In order to compare two alternatives as well as to determine optimal operating conditions, in both modes, solution flow rate, temperature, transmembrane pressure and process duration were varied independently and their influence on the permeate flux as well as on the efficiency of decolourization and purification were examined. The cross-flow filtration was carried out on ceramic tubular membrane with pore diameter of 20 nm. The obtained results have shown that permeate flux increased approximately 30%, at 80 °C, and 65%, at 70 °C, when static mixer was used. Significant part of coloured compounds—45% in average, determined by the absorbance measurement of permeate/feed, was separated from the raw sugar syrup. Decolourization in SM-mode is greater than the decolourization in NSM-mode (30% after 0.5 h and 55% after 2 h). Purity was eliminated with an efficiency of 80% in average compared to the feed, with the similar success when NSM-mode and SM-mode of operation were applied, particularly at the end of ultrafiltration.     

EFFECTS OF CO-IMMOBILIZATION OF PECTINASE AND AMYLASE ON ULTRAFILTRATION OF APPLE JUICE SIMULATE

In view of its possible application in apple juice clarification, the potential of co‐immobilized pectinase/amylase by physical adsorption on a polysulfone ultrafiltration hollow fiber was examined. Solutions containing different concentrations of pectin and starch were used. The effect of various operational parameters on the production of reducing compounds, mainly galacturonic acid and maltose, was investigated. Results indicated that relative permeate flux, during ultrafiltration of starch‐pectin solutions, was up to 35% higher when commercial pectinase and amylase were co‐immobilized on a hollow fiber membrane. Although the concentration of reaction products increased up to 50% with the pectin concentration, the same was not verified when the starch content changed from 3.85 to 5.00 mg/mL. However, the reference permeate flux was improved when starch was added to substrate, independently of its concentration. Considering the size of an average starch granule, this increase in permeate flux was attributed to the removal of pectin gel by dragging. Permeate fluxes were comparable for both batch and permeate recycling operations.     

Mass production of D-psicose from d-fructose by a continuous bioreactor system using immobilized D-tagatose 3-epimerase

An improved process for the mass production of D-psicose from D-fructose was developed. A D-fructose solution (60%, pH 7.0) was passed at 45 degrees C through a column filled with immobilized D-tagatose 3-epimerase (D-TE) which was produced using recombinant Escherichia coli, and 25% of the substrate was converted to D-psicose. After epimerization, the substrate, D-fructose, was removed by treatment with baker's yeast. The supernatant was concentrated to a syrup by evaporation under vacuum and D-psicose was crystallized with ethanol. Approximately 20 kg of pure crystal D-psicose was obtained in 60 d.     

Composition and nutritional value of commercial dried whey products from feta cheese manufacture

Various commercial dried whey products—WHEYPRO20, WHEYPRO35 and WHEYPRO65 (with approximately 20, 35 and 65% protein, respectively) and LACTINA (a permeate powder)—were studied in terms of chemical composition and nutritional value. These products were produced industrially from the whey of feta cheese manufactured with ovine and caprine milk by ultrafiltration and subsequent evaporation and spray-drying. As the protein content in these products increased, the nonprotein nitrogen and fat contents increased while the lactose and ash contents decreased. Generally the concentration of minerals (Ca, P, Na, K, Cl) in these products decreased with increasing protein content. With the exception of valine and methionine + cysteine, all essential amino acids were in excess in the whey protein concentrates (WHEYPRO35 and WHEYPRO65) as compared with the Food and Agriculture Organization reference protein and with human milk protein.     

Lactose Solubility and Crystal Growth as Affected by Mineral Impurities

Single crystal growth method was applied to determine lactose solubility, growth rate and morphology of lactose crystals grown in model lactose solutions containing various salts and in whey ultrafiltration (UF) permeate solutions. Salts either increased or decreased the lactose crystal growth rate, due to effects on lactose solubility. Addition of LiCl led to a maximum increase in growth rate and a maximum decrease in lactose solubility, while K₂HPO₄ had opposite effects. Growth rates of individual lactose crystals in whey UF permeate solutions were lower and lactose solubility higher than those in pure lactose solutions.     

Acceptance of Frozen Desserts Made with Concentrated,Decolorized, Deionized Hydrolyzed Whey Permeate

Three separate batches of whey permeate from ultrafiltration of sweet cheese whey were deionized, treated with β-galactosidase to hydrolyze lactose, and concentrated. By varying the level of completion of these steps, by decolorizing the latter two batches, and by subjecting the last batch to a 75°C postpasteurization heat treatment, control of stability and flavor was increased.The concentrated, deionized, hydrolyzed whey permeate was divided into two lots, one of which was decolorized. The regular and decolorized permeates were then used in soft-serve ice milk, hardened ice milk, and milk shake mixes. Mixes were pasteurized at 77°C for 30 min and stored at 4°C. After freezing, each underwent organoleptic evaluation and comparison with a commercial brand.Products made with regular permeate yielded satisfactory results when used only at low levels. Products made with decolorized permeate yielded better overall results, although the products were criticized for being less sweet than controls.A concentrated, deionized, hydrolyzed whey permeate product developed for sweetener applications should be economical to produce and should be highly competitive with fructose and corn syrup sweeteners.     

蔗糖异构酶基因在Escherichia coli BL21(DE3)中的表达及重组菌的细胞固定化

分别利用IPTG和乳糖两种诱导物诱导蔗糖异构酶(SIase)基因在E.coliBL21(DE3)中实现表达,对诱导温度、诱导时机、诱导物浓度、诱导持续时间进行比较分析并优化,确定了二者的最佳诱导条件,在E.coli培养3h后(OD600约为0.9)添加终浓度为0.8mmol/L的IPTG(0.5mmol/L乳糖)在20℃(24℃)条件下诱导14h(12h)能获得最高的蛋白表达量及SIase酶活。在最优条件下以IPTG为诱导物时目的蛋白占总蛋白的41.6%,单位体积培养液中SIase酶活为12.37U/mL,以乳糖为诱导物时分别为27.2%,14.72U/mL,从收获酶活角度考虑可见乳糖作为诱导物的优势;而后利用海藻酸钠包埋法固定化重组菌,转化初始浓度为500g/L的蔗糖溶液,转化10～11h后异麦芽酮糖平均得率在83%以上,蔗糖平均转化率大于99%,固定化细胞能够连续稳定转化25批次,转化效率相对于原始菌提高了近55%。     

Characterization of Physical and Mechanical Properties of Miscible Lactose‐Sugars Systems

Lactose‐sugars systems were produced by spray drying. They were lactose, lactose–glucose (4:1) mixtures, lactose–maltose (4:1) mixtures, lactose–sucrose (4:1) mixtures, lactose–trehalose (4:1) mixtures, and lactose–corn syrup solids (CSS) (4:1) mixtures. The physical characteristics, water sorption behavior, glass transition, and mechanical properties of miscible lactose‐sugars systems were investigated. Lactose–glucose mixtures had larger particle size than other lactose‐sugars systems after spray drying. The presence of glucose or sucrose in lactose‐sugars mixtures decreased the glass transition temperatures of amorphous systems, while the presence of maltose and trehalose had only minor impact on the glass transition temperatures. Moreover, glucose accelerated the crystallization of amorphous system at 0.44 a_w, but its presence delayed the loss of sorbed water at higher water activities (≥0.54 a_w). Mechanical property study indicated that glucose and sucrose in amorphous system could result in an increase of molecular mobility, while the presence of CSS could decrease the free volume and maintain the stiffness of the miscible systems.