Chemical composition and sensory analysis of cheese whey‐based beverages using kefir grains as starter culture

The aim of the present work was to evaluate the use of the kefir grains as a starter culture for tradicional milk kefir beverage and for cheese whey‐based beverages production. Fermentation was performed by inoculating kefir grains in milk (ML), cheese whey (CW) and deproteinised cheese whey (DCW). Erlenmeyers containing kefir grains and different substrates were statically incubated for 72 h at 25 °C. Lactose, ethanol, lactic acid, acetic acid, acetaldehyde, ethyl acetate, isoamyl alcohol, isobutanol, 1‐propanol, isopentyl alcohol and 1‐hexanol were identified and quantified by high‐performance liquid chromatography and GC‐FID. The results showed that kefir grains were able to utilise lactose in 60 h from ML and 72 h from CW and DCW and produce similar amounts of ethanol (～12 g L^?1), lactic acid (～6 g L^?1) and acetic acid (～1.5 g L^?1) to those obtained during milk fermentation. Based on the chemical characteristics and acceptance in the sensory analysis, the kefir grains showed potential to be used for developing cheese whey‐based beverages.     

The anti‐allergenic properties of milk kefir and soymilk kefir and their beneficial effects on the intestinal microflora

Food allergy is now recognized as a worldwide problem, and like other atopic disorders its incidence appears to be increasing. Kefir is reported to possess the ability to reduce intestinal permeation of food antigens; however, no experimental study has clearly evaluated the relationships between kefir consumption, allergen‐specific IgE response, and intestinal microflora. The aim of this study was to evaluate the effect of oral consumption of milk kefir and soymilk kefir on in vivo IgE and IgG1 production induced by ovalbumin (OVA) in mice. The effects of kefir administration on the murine intestinal microflora were also examined. Oral administration of milk kefir and soymilk kefir for 28 days significantly increased the fecal populations of bifidobacteria and lactobacilli, while it significantly decreased those of Clostridium perfringens. Milk kefir and soymilk kefir also significantly decreased the serum OVA‐specific IgE and IgG1 levels for both groups, but not those of the IgG2a analogues. Consumption of milk kefir and soymilk kefir suppressed the IgE and IgG1 responses and altered the intestinal microflora in our supplemented group, suggesting that milk kefir and soymilk kefir may be considered among the more promising food components in terms of preventing food allergy and enhancement of mucosal resistance to gastrointestinal pathogen infection. Copyright © 2006 Society of Chemical Industry     

Preparation of lactose‐free milk by using salt‐fractionated almond (Amygdalus communis) β‐galactosidase

β‐galactosidase was isolated from almond (Amygdalus communis) extract by ammonium sulfate precipitation. Almond proteins precipitated by using ammonium sulfate and then dialysed exhibited 5.3‐fold purification of β‐galactosidase, and the yield of enzyme preparation was 96.5%. The partially purified β‐galactosidase exhibited pH and temperature optima at pH 5.5 and 50 °C, respectively. The enzyme was significantly stable against heat, pH, calcium and magnesium ions and D ‐galactose. The almond β‐galactosidase preparation exhibited over 89% activity even after 2 months storage at 4 °C. Hydrolysis of lactose in milk and whey was performed in a stirred batch process by using this enzyme preparation. These observations indicated that the hydrolysis of lactose increased continuously with time. The enzyme could hydrolyse 94% of lactose in buffer solution and whey whereas 90% of lactose hydrolysis was achieved in milk. The main aim of the present study was to prepare lactose‐free milk, which must be free from contamination, and the process should be inexpensive. Copyright © 2007 Society of Chemical Industry     

Preparation of Recombined Milk Using Modified Butterfats Containing α‐Linolenic Acid

Abstract: Modified butterfats (MBFs) were produced by lipase‐catalyzed interesterification with 2 substrate blends (6:6:8 and 4:6:10, by weight) of anhydrous butterfat (ABF), palm stearin, and flaxseed oil in a stirred‐batch type reactor after short path distillation. The 6:6:8 and 4:6:10 MBF contained 21.7% and 26.5%α‐linolenic acid, respectively. Total saturated fatty acids of the MBFs ranged from 41.4% to 47.4%. The cholesterol contents of the 6:6:8 and 4:6:10 MBFs were 21.0 and 12.1 mg/100 g, respectively. In addition, the melting points of the 6:6:8 and 4:6:10 MBFs were 32 °C and 31 °C, respectively. After preparation of recombined milks (oil‐in‐water emulsions) with MBFs, the stability of emulsions prepared with the MBFs (6:6:8 and 4:6:10) was compared to those with ABF during 10‐d storage at 30 °C. Skim milk powder (containing 1% protein) was added to prepare emulsions as an emulsifier. Microstructures of emulsions freshly prepared with the ABF and the MBFs consisted of uniform fat globules with no flocculation during 10‐d storage. With respect to fat globule size distribution, the volume‐surface mean droplet diameter (d₃₂) of the 6:6:8 and 4:6:10 MBF emulsions ranged between 0.33 and 0.34 μm, which was similar to the distribution in ABF emulsion. Practical Application: Milk, an expensive dairy food, has been widely used in various milk‐derived food products. Modified butterfats (MBFs) contain α‐linolenic acid as an essential fatty acid. Emulsion stability of recombined milks (oil‐in‐water emulsions) with MBFs was similar to that in anhydrous butterfat emulsion during 10‐d storage. They may be a promising alternative for reconstituted milks to use in processed milk‐based products.     

Effect of storage parameters on freeze‐dried kefir grains

The purpose of this study was to use freeze‐drying to preserve microbial activity while extending the shelf life of kefir grains and to determine the best storage temperature. Freeze‐dried kefir grains were lyophilised and were later stored in a multilayer plastic film with a moisture barrier for 90 days at varying temperatures. Microbial activity continued until the 60^th day of storage at 4 °C. PCR analysis was performed to determine Lactobacillus kefiranofaciens as an indicator kefir micro‐organism. It was concluded that the conservation of kefir grains by freeze‐drying protects the natural embedded microbiota; therefore, both the shelf life of kefir grains and the consumption of natural kefir increase.     

Studies on the interaction of ‐epigallocatechin‐3‐gallate from green tea with bovine β‐lactoglobulin by spectroscopic methods and docking

The binding interaction between‐epigallocatechin‐3‐gallate (EGCG) and bovine β‐lactoglobulin (βLG) was thoroughly studied by fluorescence, circular dichroism (CD) and protein–ligand docking. Fluorescence data revealed that the fluorescence quenching of βLG by EGCG was the result of the formation of a complex of βLG–EGCG. The binding constants and thermodynamic parameters at two different temperatures and the binding force were determined. The binding interaction between EGCG and βLG was mainly hydrophobic and the complex was stabilised by hydrogen bonding. The results suggested that βLG in complex with EGCG changes its native conformation. Furthermore, preheat treatment (90 °C, 120 °C) and emulsifier (sucrose fatty acid ester) all boosted the binding constants (K_a) and the binding site values (n) of the βLG‐EGCG complex. This study provided important insight into the mechanism of binding interactions of green tea flavonoids with milk protein.     

Influence of whey peptides on the surface activity of κ‐casein and β‐lactoglobulin A

Whey protein hydrolysate (WPH) was fractionated by reverse‐phase chromatography to obtain fractions of varying surface‐hydrophobicities. A model oil–water interface (MI) was pre‐coated with the WPH or fractions thereof. Contact angle (θ) of sessile drops of κ‐casein (κ‐CN) or β‐lactoglobulin A (β‐LGA) were measured on the MI. Pre‐coating of MI with un‐fractionated WPH decreased θ, that is, increased surface activity, of both κ‐CN (35–8.3°) and β‐LGA (38–21.3°). Conversely, pre‐coating of MI with the fractions significantly increased θ of both proteins as a function of hydrophobicity. Data provide insight into variability of whey protein functionality in food applications.     

The Variation of β‐amylase Activity and Protein Fractions in Barley Grains as Affected by Genotypes and Post‐anthesis Temperatures

The variation of β‐amylase activity and protein fractions in barley grains was evaluated using 148 barley genotypes grown in the field and two cultivars under in vitro culture with two temperature treatments during grain development. The results showed that there was significant genotypic variation in β‐amylase activity and protein fraction content. Regression analysis indicated that β‐amylase activity was positively correlated with total protein and the level of each of the protein fractions, with the correlation coefficient between β‐amylase activity and hordein content being the highest. Furthermore, higher post‐anthesis temperatures (32/26°C, day/night) significantly enhanced β‐amylase activity and protein fraction content, presumably as a result of reduced starch content. Albumin and glutelin were the least and most affected, respectively, in comparison with the plants under lower temperature (22/16°C). Temperature post‐anthesis also influenced the morphology of the starch A granule and the number of B granules, suggesting the altered starch structure may also be a reason for deteriorated malting quality under high temperatures.     

Instrumental Textural Profile Analysis of Soy Fortified Pressed Chilled Acid Coagulated Curd (Paneer)

Abstract

Studies were conducted to observe the effect of varying fat content in milk (0–6%) and varying proportion of soy milk (7.5°B, 0–40%) in the blend on the textural properties of Soy Fortified Paneer (SFP). Instrumental Texture Analyzer of Stable Micro System was used to measure the texture of paneer containing varying level of fat and soy solids for texturel profile analysis (TPA). Texture profile data, thus obtained, were used to develop regression models between fat content in milk and proportion of soy milk in blend with that of the dependent variable hardness, cohesiveness, chewiness, springiness and adhesiveness. The high correlation coefficients of each developed model confirmed its suitability in representing experimental data. Based on to these models SFP samples prepared using a blend (15:85 v/v) of soy milk (7.5°B) and buffalo milk (3.12%) was found to be suitable for producing textural characteristics similar to that of control paneer sample.     

Influence of adjunct cultures on angiotensin‐converting enzyme (ACE)‐inhibitory activity,organic acid content and peptide profile of kefir

The angiotensin‐converting enzyme (ACE)‐inhibitory activities, peptide profiles and organic acid contents in kefir produced by kefir grains plus lactic acid bacteria as adjunct cultures were determined. All the kefir samples showed almost similar peptide profiles as detected by RP‐HPLC, but quantitative differences were observed during storage. The ACE‐inhibitory activities of different lactic cultures did not exhibit a linear tendency during storage period. After 7 days of storage, there was a significant increase in ACE‐inhibitory activity of the sample fermented with Lactobacillus helveticus. However, a kefir sample containing Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis exhibited a higher ACE‐inhibitory activity (92.23%) compared to the other samples.     

Formation of oil‐in‐water (O/W) pickering emulsions via complexation between β‐cyclodextrin and selected organic solvents

Cyclodextrins (CDs) are cyclic oligosaccharides derived from the enzymatic degradation of starch. Emulsifying functionality of β‐cyclodextrin (β‐CD) upon its complexation with selected solvents (octanol, decane, and toluene) was studied. In several tests, the three‐phase systems containing the emulsion fraction in the middle position were obtained. The examination of variations in the phase behavior of the test systems showed that the decane/β‐CD/water system had the highest emulsion phase volume when β‐CD at concentration of 10% w/v was used. A reduction in interfacial tension (IFT) of the oil–water interface in each test system was observed with the following order: toluene, decane, and octanol. The precipitated fraction obtained upon centrifugation of the emulsion phase, was structurally characterized as the inclusion complex (IC) formed between β‐CD and each of the three test solvents. The wettability of the IC particles was determined through contact angle measurement and formation of the oil‐in‐water (O/W) Pickering emulsions was confirmed (θ_ow<90°). With use of size distribution data, the ICs particles as the microparticles (1–10 µm) were found to be the main species involved in the formation and stabilization of the emulsions.     

Physico‐Chemical and Structural Characteristics of Vegetables Cooked Under Sous‐Vide,Cook‐Vide,and Conventional Boiling

In this paper, physico‐chemical and structural properties of cut and cooked purple‐flesh potato, green bean pods, and carrots have been studied. Three different cooking methods have been applied: traditional cooking (boiling water at 100 °C), cook‐vide (at 80 and 90 °C) and sous‐vide (at 80 °C and 90 °C). Similar firmness was obtained in potato applying the same cooking time using traditional cooking (100 °C), and cook‐vide and sous‐vide at 90 °C, while in green beans and carrots the application of the sous‐vide (90 °C) required longer cooking times than cook‐vide (90 °C) and traditional cooking (100 °C). Losses in anthocyanins (for purple‐flesh potatoes) and ascorbic acid (for green beans) were higher applying traditional cooking. β‐Carotene extraction increased in carrots with traditional cooking and cook‐vide (P < 0.05). Cryo‐SEM micrographs suggested higher swelling pressure of starch in potatoes cells cooked in contact with water, such as traditional cooking and cook‐vide. Traditional cooking was the most aggressive treatment in green beans because the secondary walls were reduced compared with sous‐vide and cook‐vide. Sous‐vide preserved organelles in the carrot cells, which could explain the lower extraction of β‐carotene compared with cook‐vide and traditional cooking. Sous‐vide cooking of purple‐flesh potato is recommended to maintain its high anthocyanin content. Traditional boiling could be recommended for carrots because increase β‐carotenes availability. For green beans, cook‐vide, and sous‐vide provided products with higher ascorbic acid content.     

Effects of poly‐γ‐glutamic acid on the physicochemical characteristics of skim milk yoghurt

The physicochemical and sensory properties of skim milk yoghurts containing poly‐γ‐glutamic acid (PGA) at different levels (0.0025, 0.005 and 0.01%) were evaluated. Addition of PGA up to 0.01% to reconstituted skim milk (11%, w/v) did not affect the growth of lactic acid bacteria or the development of titratable acidity in yoghurt, whereas full‐fat control yoghurt had reduced acid production. No changes were found in viable cell counts of PGA yoghurts during storage (4 weeks at 4 °C). The addition of PGA (0.005%) significantly decreased syneresis in skim milk yoghurt and did not cause any undesirable effects in sensory acceptability.     

Inhibitor‐Assisted High‐Pressure Inactivation of Bacteria in Skim Milk

The combined inactivation effects of high hydrostatic pressure (HHP) and antimicrobial compounds (potassium sorbate and ε‐polylysine [ε‐PL]) on 4 different bacterial strains present in skim milk and the effect of these treatments on milk quality were investigated in this study. HHP treatment at 500 MPa for 5 min reduced the populations of Escherichia coli, Salmonella enterica Typhimurium, Listeria monocytogenes, and Staphylococcus aureus from 6.5 log colony‐forming units (CFUs) or higher to less than 1 log CFU/mL. Compared to HHP alone, HHP with potassium or ε‐PL resulted in significantly higher reductions in the bacterial counts. After 5 min of treatment with HHP (500 MPa) and ε‐PL (2 mg/mL), no growth of E. coli, S. enterica Typhimurium, or L. monocytogenes in skim milk was observed during 15 d of refrigerated storage (4 ± 1 °C). Scanning electron microscopy analysis revealed that the synergistic treatments caused more serious damage to the bacterial cell walls. Quality assessments of the treated samples indicated that the combined treatments did not influence the color, the turbidity, the concentrations of –SH group of the proteins, or the in vitro digestion patterns of the milk. This study demonstrates that HHP with potassium or ε‐PL may be useful in the processing of milk or milk‐containing foods.     

RAPID HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC DETECTION OF FUROSINE (ε‐N‐2‐FUROYLMETHYL‐L‐LYSINE) IN YOGURT AND CHEESE MARKETED IN TURKEY*

Furosine (ε‐N‐2‐furoylmethyl‐L‐lysine) content determination in the yogurt and different cheese types (pickled white, kasar, processed, canned tulum, blue‐veined and mozzarella cheeses) marketed in Turkey was performed using ion‐pair reversed‐phase high performance liquid chromatography (RP‐HPLC). Calibration study (R² = 0.9999), analytical method validation and recovery studies gave satisfactory results. The lowest furosine values were observed in pickled white cheeses (5.35 ± 0.01 to 7.28 ± 0.02 mg/100 g protein). All cheeses except pickled white showed furosine values between 182.16 ± 0.12 (canned tulum) and 261.32 ± 0.10 mg/100 g protein (ripened kasar). The highest content of furosine was observed in whole yogurt (316.47 ± 0.17 mg/100 g protein) which could be because of severe heat treatment and the addition of milk powder during the manufacturing process. The method provides a rapid, reproducible and accurate determination of this Amadori compound (ε‐deoxy‐fructosyl‐lysine) in yogurt and cheese samples.     

Oscillatory Rheology and Creep Behavior of Barley β‐d‐glucan Concentrate Dough: Effect of Particle Size,Temperature, and Water Content

Small amplitude oscillatory rheology and creep behavior of β‐glucan concentrate (BGC) dough were studied as function of particle size (74, 105, 149, 297, and 595 μm), BGC particle‐to‐water ratio (1:4, 1:5, and 1:6), and temperature (25, 40, 55, 70, and 85 °C). The color intensity and protein content increased with decreasing particle size by creating more surface areas. The water holding capacity (WHC) and sediment volume fraction increased with increasing particle size from 74 to 595 μm, which directly influences the mechanical rigidity and viscoelasticity of the dough. The dough exhibited predominating solid‐like behavior (elastic modulus, G′ > viscous modulus, G″). A discrete retardation spectrum is employed to the creep data to obtain retardation time and compliance parameters, which varied significantly with particle size and the process temperature. Creep tests exhibited more pronounced effect on dough behavior compared to oscillatory measurement. The protein denaturation temperature was insignificantly increased with particle fractions from 107 to 110 °C. All those information could be helpful to identify the particle size range and WHC of BGC that could be useful to produce a β‐d ‐glucan enriched designed food.     

Expression analysis of endo‐1,4‐β‐glucanase genes during aril breakdown of harvested longan fruit

BACKGROUND: The aim of the present study was to investigate the expression profiles of three endo‐1,4‐β‐glucanase (EGase, EC 3.2.1.4) genes during aril breakdown of longan fruit stored at room temperature (25 °C), low temperature (10 °C) or on transferring fruit stored at 10 °C for 20 days to 25 °C. RESULTS: Three longan full‐length cDNAs, designated Dl‐EGase1, Dl‐EGase2 and Dl‐EGase3, were isolated and characterized. EGase activity in aril tissues of longan fruit increased with the appearance of aril breakdown symptoms, while RNA gel blot analysis revealed that the accumulations of three Dl‐EGase genes exhibited differential characteristics with the occurrence of aril breakdown. Dl‐EGase2 may be involved in the aril breakdown in longan fruit at the later stage of storage at room temperature. Conversely, expression of Dl‐EGase3 could be mainly involved in aril breakdown of fruit stored at 10 °C. In addition, Dl‐EGase3 and Dl‐Egase2 were related to the aril breakdown of fruit transferred from low temperature to room temperature. CONCLUSION: The results obtained in this study indicate that Dl‐EGase genes are involved in the aril breakdown of longan fruit and that considerable variation exists between expression patterns of individual members of the EGase gene family. Copyright © 2009 Society of Chemical Industry     

Electrospun nanofibers from cyclodextrin inclusion complexes with cineole and p‐cymene: enhanced water solubility and thermal stability

The electrospinning of self‐standing nanofibrous webs from inclusion complexes (IC) of cineole and p‐cymene with two modified cyclodextrins (HPβCD, HPγCD) was achieved without using carrier polymeric matrix. Although they are highly volatile, certain amount of cineole and p‐cymene was protected in cyclodextrin inclusion complexes nanofibers (CD‐IC‐NF). That is, 68.4%, 78.1%, 54.5% and 44.0% (w/w) of active agent were preserved in cineole/HPβCD‐IC‐NF, cineole/HPγCD‐IC‐NF, p‐cymene/HPβCD‐IC‐NF and p‐cymene/HPγCD‐IC‐NF, respectively. Remarkable, high thermal stability for cineole (~150 °C – 270 °C) and p‐cymene (~150 °C – 275 °C) was achieved for CD‐IC‐NF samples due to CD‐IC formation. The water solubility of cineole and p‐cymene was significantly improved by inclusion complexation where CD‐IC‐NF samples become readily dissolved in water. In brief, essential oils and flavours such as cineole and p‐cymene could be applicable in food and oral care applications owing to their fast‐dissolving behaviour along with high water solubility, enhanced thermal stability and free‐standing feature of CD‐IC‐NF webs.     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.