Determination of Antioxidant Capacity of Unprocessed and Processed Food Products by Spectrophotometric Methods

Two electron transfer (ET) reaction-based methods, ferric reducing antioxidant power (FRAP) and Folin–Ciocalteu (FC) reducing capacity, were used for the determination of total antioxidant capacity of vegetable oils (rapeseed, palm and extra virgin olive oils), meat samples (poultry and pork) and potatoes before and after the frying process under domestic frying conditions. Before frying, potatoes had the highest FRAP value (276.7 μmol Trolox/100 g), whereas extra virgin olive oil revealed the highest Folin–Ciocalteu Index (FCI = 443.2 μmol Trolox/100 g). Antioxidant capacity of methanolic extracts of raw meat (9.0–9.4 μmol Trolox/100 g and 135.7–160.1 μmol Trolox/100 g for FRAP and FC methods, respectively) was lower than FRAP (133.4–149.6 μmol Trolox/100 g) and FCI (156.2–443.2 μmol Trolox/100 g) of unheated rapeseed and extra virgin olive oils. However, antioxidant capacity of the studied food samples changed after frying process. Positive correlations (correlation coefficients ranged between 0.5742 and 0.9942) were found between the two analytical methods used to determine the antioxidant capacity of unprocessed and processed food products. The results of principal component analysis (PCA) indicate that there are differences between total amounts of antioxidants in raw and fried food products.     

Glycation compounds in peanuts

In the present study, the extent of the Maillard reaction in peanuts was investigated, using N-ε-fructosyllysine (ε-Fru-Lys, determined via furosine) as an indicator for the early stage, and pyrraline and N-ε-carboxymethyllysine (CML) as representatives for advanced glycation. In commercial samples, ε-Fru-Lys ranged between 1.5 and 13.3 mmol/mol lysine. Pyrraline was found in amounts between not detectable (below 0.3 mmol/mol lysine) and 9.0 mmol/mol lysine, and CML between 0.8 and 2.7 mmol/mol lysine. Lysine modification by glycation products was very low in cooked and fried peanuts (below 1%). In laboratory-scale roasting experiments, the amount of ε-Fru-Lys reached maximum values of 12.0 mmol/mol lysine after 20 min at 160 °C, whereas pyrraline increased up to 38.5 mmol/mol lysine after 25 min at 170 °C. Amount of CML was up to 1.8 mmol/mol lysine in peanuts roasted for 25 min at 170 °C. Such high amounts of pyrraline have not yet been described for any other food item. Only about one tenth of the totally observed lysine modification of up to 50% can be explained by the three glycation compounds, indicating that currently unknown reactions occur during peanut roasting. Reactions between proteins and carbonyl compounds, most likely originating from oxidative degradation of lipids, may play an important role for lysine derivatization in peanuts and should be analyzed more in detail.     

Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998     

Protein profiles and total antioxidant capacity of water‐soluble and water‐insoluble fractions of white brined goat cheese at different stages of ripening

This study deals with proteolysis and total antioxidant capacity of proteins of white brined cheese prepared from overheated goat milk and ripened for fifty days. Proteolytic changes were reflected through the relatively low level of soluble nitrogen (50 days ripened cheese had 15.32 g/100 g of water‐soluble nitrogen, 8.1 g/100 g of TCA‐soluble nitrogen and 2.69 g/100 g of PTA‐SN), intensive proteolysis of α_s2‐CN during initial 10 days of ripening (up to 50.70% of initial content) and its much slower degradation through further 40 days, slow but continual decrease of β‐CN content (up to 85.14% of residual content) and high level of proteolytic products tightly bounded into gel network. Total antioxidant capacity of water‐soluble and water‐insoluble fractions increased after cheese ripening. These findings could be useful for better understanding and control over the production of white brined goat cheese as highly valuable functional product.     

Proteolysis,texture and colour of a raw goat milk cheese throughout the maturation

Changes on chemical and textural parameters were studied throughout maturation of PDO Ibores cheese. NCN/TN (non-casein nitrogen/total nitrogen) values were significantly modified (P < 0.001) throughout maturation, and significantly, lower values were observed at day 1 than at day 30, 60 and 90. Non-protein nitrogen/total nitrogen (NPN/TN) was not significantly changed during the ripening process (P > 0.05). Therefore, proteolysis extent (casein degradation and ‘ripening depth’) took place at initial stage and was limited throughout Ibores cheese maturation. In addition, since casein nitrogen decreased during the first month of ripening without a simultaneous increase in NPN/TN, this likely indicates that the large fragments of caseins liberated during this period are not further degraded into smaller products. Primary proteolysis (resulting from the action of endoproteases on caseins) is thus far more important than secondary proteolysis during this period. Moreover, secondary proteolysis remains limited along the 90 days. Polypeptide nitrogen significantly increased at day 30 from casein degradation compared to day 1, while free amino acids (FAA) content significantly increased during maturation process. In addition, hardness and adhesiveness values significantly increased, but cohesiveness and springiness significantly decreased up to day 60. Variables such as dry matter, NCN/TN and polypeptide nitrogen showed high correlations with textural parameters. Principal component analysis (PCA) of variables divided the Ibores cheeses according to their ripening: early, middle or late ripening.     

Effect of lactobacillus fermented beetroot juice on composition and activity of cecal microflora of rats

This study aimed at determination of the effect caused by ingestion of beetroot juice fermented by Lactobacillus casei 0920 and Lactobacillus brevis 0944 strains on the state of cecal ecosystem of experimental rats. The intake of fermented beetroot juice containing 3.5–4.0 × 10⁹ CFU/mL live Lactobacillus sp. cells positively modulated the cecal microflora of the rats and its metabolic activity. The counts of Lactobacillus sp., Bifidobacterium sp., Bacteriodes sp., and Enterococcus sp. were maintained at the level of 8.2–8.6, 6.2–7.5, 8.0–8.3, and 7.3–7.7 log units, respectively, while the number of Clostridium sp. cells was increased by 1.1–1.6 log units and Enterobacteriaceae bacteria were reduced by 0.8–2.1 log units. In this study, the selected cecal enzymes such as β-glucosidase, β-glucuronidase, and β-galactosidase as well as the profile and concentration of short chain fatty acids (SCFA) were the biochemical markers of metabolic activity of the intestinal ecosystem. The considerable decrease in activities of β-glucosidase and β-glucuronidase was observed in all three experimental groups fed with the fermented beetroot juice. Total concentration of SCFA was the highest (78.1 μmol/100 g BW vs. 59.2 μmol/100 g BW in control group) in intestines of rats fed with 6 mL of fermented beetroot juice daily. These results prove that the fermented beetroot juice benefits cecal microbial activity.     

Homocysteine in food

Nutritional factors can elevate the concentration of homocysteine in plasma, which is regarded as a risk indicator for cardiovascular events and other degenerative diseases. Although alimentary methionine is believed to be the main source for plasma homocysteine, the literature is lacking information about the homocysteine content of daily food. In this paper, the total homocysteine content of some commercially available food items such as tuna, swine liver, roquefort cheese, coffee, beer and white bread was measured by RP-HPLC with fluorescence detection after pre-column derivatization with a thiol-specific sulfonylbenzofuran, namely 7-benzo-2-oxa-1,3-diazole-4-sulfonic acid (SBD-F). With the exception of coffee, all examined food contained homocysteine in amounts between 30 and 950 μg per kg, which was 2,000–10,000-fold compared to the methionine content of the respective food. Based on a hypothetical daily consumption of the investigated foods, a maximum daily intake of homocysteine ranging from 400 to 700 μg or 3–5 μmol could be estimated. Compared to plasma homocysteine levels of 6–9 μmol/l, we conclude that the amount of alimentary homocysteine has only a very slight significant impact on the plasma homocysteine level even if complete resorption of the thiol compound is assumed.     

Characterization of Siahmazgi cheese,an Iranian ewe's milk variety: Assessment of physico-chemical,textural and rheological specifications during ripening

Siahmazgi cheese is an Iranian locally-made cheese produced from ewe's milk or a mixture of ewe and goat's milks in the suburbs of Rasht in the north of Iran. This kind of cheese is kept in sheepskin for six months under special condition which cause distinct physicochemical and textural characteristics. Therefore, in the present study the effect of ripening time (6 months) on the chemical, physicochemical, rheological and textural characteristics of Siahmazgi cheese (18 samples) was investigated. The rheological and textural properties were determined using rheometer (frequency sweep) and texture analyzer (uniaxial compression). Based on our findings, the measured values including pH, titratable acidity (TA), dry matter, fat, protein, ash, salt content, water soluble nitrogen in total nitrogen, and non-protein-nitrogen in total nitrogen significantly increased during ripening (P < 0.05). Furthermore, the results showed that the six-month ripened Siahmazgi cheese contained high values of dry matter (59.95 ± 0.08 g/100 g), salt (5.65 ± 0.05 g/100 g), and ash (7.24 ± 0.02 g/100 g). Regarding rheological and textural properties, storage modulus (G′), loss modulus (G″), fracture stress (σ_f) and firmness increased while loss tangent and fracture strain decreased.     

Determination of synergistic effects of polymethoxylated flavone extracts of Jinchen orange peels (<Emphasis Type="Italic">Citrus Sinensis</Emphasis> Osberk) with amino acids and organic acids using chemiluminescence

Antioxidant capacity of polymethoxylated flavones (PMFs) extracts of Jinchen orange peels (Citrus sinensis Osberk) was evaluated by using a chemiluminescence (CL) method in vitro. PMFs were isolated using a procedure that produced a consistent mixture of PMFs both in identity and in proportion. The mixture mainly consisted of nobiletin (55.9%), sinensetin (15.2%), heptamethoxyflavone (13.2%), and tangeretin (8.1%). The antioxidative effects of PMFs and the main individual flavones in PMFs as well as synergistic effects of PMFs with organic acids (citric acid, oxalic acid, and malic acid) and amino acids (alanine, lysine, serine, and threonine) on superoxide anion were determined by the pyrogallol–luminol system. The results showed that the inhibition by PMFs on superoxide radical was stronger than that of the individual flavones. Mixtures of citric acid and lysine with PMFs had higher synergistic effects than any other tested mixtures, and the optimum concentrations were exhibited by combinations of 7 μg/mL PMFs + 120 μg/mL citric acid (1.2, p < 0.05) and 7 μg/mL PMFs + 42 μg/mL lysine (1.1, p < 0.05). For the other amino acids and organic acids, the values of the measured inhibition effect (% MIE) of the mixtures with PMFs were not significantly different from their expected inhibition effect (% EIE), which did not show synergism.     

Evaluation of aeration and substrate concentration on the production of carotenoids by <Emphasis Type="Italic">Sporidiobolus salmonicolor</Emphasis> (CBS 2636) in bioreactor

This study aimed at optimising the cultivation conditions for the production of carotenoids by Sporidiobolus salmonicolor (CBS 2636) in a bioreactor. The maximum content of total carotenoids in the full factorial design 22 was 3131.3 μg/L in synthetic medium with 80 g/L of glucose, 15 g/L of peptone, 5 g/L of malt extract, aeration of 1.5 vvm, agitation of 180 rpm, initial pH of 4.0 at 25 °C. In the kinetic study, we could observe that the bioproduction of carotenoids is associated with cell growth in the exponential phase, and the average specific growth (μ) in bioreactor is 0.046 h⁻¹ with a maximum yield of 0.19 g cells/L h. The maximum yield of carotenoids (60.0 μg/Lh) is observed at 50-h bioproduction. The conversion factor for total organic carbon (TOC) in cells (Y_X/_SCOT) was 2.97 g/g (0–50 h) and 0.254 g/g (50–100 h), the conversion factor glucose into cells (Y_X/Sglicose) was 0.168 g/g (0–100 h). The specific production of carotenoids (Y_P/_X) was 390 μg of carotenoids per gram of cells, the conversion factor of carbon in the product (Y_P/SCOT) was 107.8 μg/g (0–50 h) and 34.4 μg/g (50–100 h), whereas the factor Y_P/_Sglicose was 69.59 μg/g. The agitation and aeration provided better homogeneity in the culture medium, and hence greater availability of nutrients and oxygen, leading to higher production of carotenoids.     

Antioxidant capacity and antioxidative compounds in barley (<Emphasis Type="Italic">Hordeum</Emphasis><Emphasis Type="Italic">vulgare</Emphasis> L.) grain optimized using response surface methodology in hot air roasting

Response surface methodology was used to predict optimum conditions for hot air roasting of barley grains (temperature, time, and amount). Antioxidant capacity in the grains was highest under optimum conditions of 250 °C, 63.5 min and 42 g (one and a half layers). A correlation of R ² = 0.74 (p < 0.05) was found between 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic contents. Ethanol and aqueous extracts were prepared from grains roasted under optimum conditions and assessed for antioxidant capacity. Antioxidative compounds in the extracts were then identified using GC–MS. The IC₅₀ value of ethanol extract was significantly lower (11.45 μg mL^–1) than that of aqueous extract (33.54 μg mL^–1) and α-tocopherol (12.6 μg mL^–1) but higher than BHT (9.59 μg mL^–1). The same trend was observed in linoleic acid assay. In reducing power, the ethanol extract and α-tocopherol were not significantly different. Phenolic acids p-hydroxybenzaldehyde, vallinic and gallic acids were identified as the major compounds in the extracts. The results obtained from this study show that it is possible to optimize antioxidant capacity in barley grains during roasting.     

Pre-treatment methods of Edam cheese milk. Effect on cheese yield and quality

The effect of high-temperature heat treatment (HH), microfiltration (MF) and ultrafiltration (UF) on the Edam vat milk composition, processing and cheese yield, ripening and functional characteristics were studied. The protein level of the MF and UF cheese milk was adjusted to 42 g/kg, whereas the level in the reference (REF) and HH milk was 34 g/kg. The cheese yield from ultrafiltration and microfiltration milk (CY_v) was 12.8 g/100 g milk, yield from reference and high-temperature heat treatment milk was 10.1 and 10.2 g/100 g milk, respectively. The adjusted cheese yield (ACY_r), calculated from raw milk, was lowest when MF was used. The pre-concentration method had little effect on the starter activity: no differences were observed in the pH of cheeses. The compositions of the ripened cheeses were comparable. The casein to fat ratio of MF cheese was elevated, possibly due to elevated casein to fat ratio of vat milk. Even though the high-temperature heat treatment, ultrafiltration and microfiltration cheeses were harder than reference cheese, they retained their elasticity. Resilience was significantly higher with microfiltration and ultrafiltration cheeses. The sensory quality of all cheeses was considered according to specification. The pre-treatment methods had little effect on the processing characteristics, cheese quality or yield when calculated on the basis of the quantity of original milk.     

Utilisation of attenuated total reflectance MIR and front-face fluorescence spectroscopies for the identification of Saint-Nectaire cheeses varying by manufacturing conditions

Twelve samples of cheeses (three types of Saint-Nectaire PDO cheeses and Savaron cheeses) differing by manufacturing and ripening conditions, from 12 different producers, were characterised by attenuated total reflectance mid-infrared (MIR) and front-face fluorescence spectroscopies, dynamic testing rheology and physico-chemical analysis. Fluorescence spectra (tryptophan residues, vitamin A and riboflavin) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region) and 1,500–900 cm⁻¹ (fingerprint region)) spectra were recorded on cheese samples. The potential of the data tables was investigated for discriminating the four different groups of cheeses. The results of factorial discriminant analysis (FDA) performed on the fluorescence and mid-infrared spectra showed a good discrimination of the four cheese groups. Considering cross-validation results, the best classifications (100%) were achieved from mid-infrared and fluorescence spectra, while only 91.7 and 72.2% of correct classification were obtained by applying FDA to rheology and physico-chemical data, respectively. Spectroscopic techniques could provide useful fingerprints and allow the identification of investigated cheeses according to manufacturing conditions. Simple and rapid spectroscopic methods offer a promising approach to the authentication of cheeses.     

Seasonal bioaccumulation of toxic trace elements in economically important fish species from the Caspian Sea using GFAAS

This study aimed to determine the concentrations of aluminium, cadmium, lead and nickel in edible muscle of three commercially valuable fish species (Rutilus frisii kutum, Liza aurata and Cyprinus carpio) from four fishing sites of Iranian coastal waters of the Caspian Sea during winter and summer. The samples were analyzed using graphite furnace atomic absorption spectrometry (GFAAS) after wet-ashing digestion. The results were expressed as μg/g of wet weight. The resulted range of metals in fish species was between 0.89–2.46 μg/g for aluminium, 0.03–0.17 μg/g for cadmium, 0.21–0.38 μg/g for lead and 0.12–0.52 μg/g for nickel. Seasonal variation influenced concentration of the metals in fish samples of some fishing sites. The highest concentrations found were 4.63 μg/g for aluminium in winter and 0.82 μg/g for lead in summer in Cyprinus carpio; while cadmium (0.49 μg/g) and nickel (1.14 μg/g) were the highest in Rutilus frisii kutum in winter. This demonstrates that estimated daily and weekly intakes of aluminium, lead and nickel and estimated monthly intake of cadmium via consumption of fish flesh are below the established PTDI, PTWI and PTMI values.     

Maribo cheese manufactured with concentrated milk: characteristics, maturation and yield

Research was carried out to study the feasibility of making maribo cheese using milk fortified by the addition of skim milk powder. A control (T-C) with 82 g l^-1 solids-non-fat (SNF) and 32 g l^-1 milk fat was included, along with three treatments with 11.7 (T-1), 14.6 (T-2) and 16.6 g l^-1 SNF (T-3) and standardization of the milk fat. Some chemical characteristics of the cheese milks and of the endproducts were studied and, in addition, cheese yield and the progress of maturation were monitored. It was observed that, as maturation proceeded in all treatments, there was a steady increase in the ripening index (soluble nitrogen/total nitrogen %), which indicates a progressive advance of proteolysis. Nevertheless, there were significant differences (p <.05) between the ripening indices of the control and the rest of the treatments. Furthermore, as the extent of maturation increased, α_sl-casein was degraded more than β-casein. The yield of cheese increased proportionally as the concentration of non-fat-solids in the milk increased.     

Effects of Maillard reaction conditions on the antigenicity of α-lactalbumin and β-lactoglobulin in whey protein conjugated with maltose

The effects of Maillard reaction conditions (weight ratio of protein to sugar, temperature and time) on the antigenicity of α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) in conjugates of whey protein isolate (WPI) with maltose were investigated. Response surface methodology was used to establish models to predict the antigenicity of α-LA and β-LG and find an optimal reaction condition under which the antigenicity of α-LA and β-LG reduces to minimum value. Conjugating WPI with maltose was an effective way to reduce the antigenicity of α-LA and β-LG. The antigenicity of α-LA decreased from 32.25 μg mL⁻¹ to 10.91 μg mL⁻¹. And the antigenicity of β-LG decreased from 272.4 μg mL⁻¹ to 38.17 μg mL⁻¹. Temperature had the greatest effect on the antigenicity of α-LA, while weight ratio of WPI to maltose was the most significant factor on the antigenicity of β-LG.     

Effect of Processing Methods on the In Vitro Protein Digestibility and Vitamin Content of Edible Winged Termite (<Emphasis Type="Italic">Macrotermes subhylanus</Emphasis>) and Grasshopper (<Emphasis Type="Italic">Ruspolia differens</Emphasis>)

The influence of processing methods of toasting and solar drying on the in vitro protein digestibility and vitamins content of edible winged termites, green grasshoppers, and brown grasshoppers consumed in Siaya, district of Kenya, was determined using standard methods. Analysis was done on fresh, toasted, toasted dried, and fresh dried insect samples. There was no significant change (p > 0.05) in protein digestibility in the termite samples, while a significant decrease (p ≤ 0.05) in the grasshopper samples was observed on toasting and drying. There was a significant reduction (p ≤ 0.05) in riboflavin content with 4.18 mg/100 g in fresh termites, 2.76 mg/100 g in toasted termites, 2.26 mg/100 g in fresh dried termites, and 1.50 mg/100 g in toasted dried termites on processing. There was also a significant reduction (p ≤ 0.05) in niacin content in the grasshoppers with 3.61 mg/100 g in fresh green grasshopper, 3.28 mg/100 g in toasted green grasshopper, 3.22 mg/100 g in fresh dried green grasshoppers, and 3.06 mg/100 g in toasted dried green grasshoppers. A significant reduction (p ≤ 0.05) in retinol content with 2.24 μg/g in fresh termites, 1.56 μg/g in toasted termites, 1.02 μg/g in toasted dried termites, and 0.98 μg/g in fresh dried termites was also reported. The processing methods of the insects affected their nutrient potential as evidenced by the changes in protein digestibility and vitamins content. Therefore, optimal processing methods need to be investigated even as we promote commercialization of these insects.     

Ripening time estimation of Kariesh cheese

Kariesh cheese is a popular cheese in Egypt produced by acid coagulation of milk. It can be consumed fresh or after ripening. Proteolysis in cheese was measured by determining soluble nitrogen (SN), amino acid nitrogen (AAN), total amino acids (TAA) and free amino acids (FAA). SN, AAN and FAA increased during ripening. Free amino acids profile revealed in total 16 amino acids and the same distribution of free amino acids. Cheese ripening was influenced by the type of milk and the method of production. The mildly acid sweet flavour was attributed to the concentration of glutamic acid, aspartic acid, proline and valine. Linear regression analysis was carried out to estimate the ripening time of this cheese. A positive correlation between the accumulation of amino acid and ripening time was established. The highest coefficient of determination near one resulted from glutamic acid (R² = 0.99) followed by lysine (R² = 0.97–0.99), then aspartic acid (0.90–0.98). From the linear regression equation for glutamic acid, lysine, aspartic acid or proline, the ripening time of Kariesh cheese in weeks was determined as follows: Time of ripening [weeks] = mg amino acid 100 g cheese-a/b where b = slope and a = intercept of regression straight line at 0 time.     

Study on the behavior of the trace metal and macro minerals in Mytilus galloprovincialis as a bioindicator species: the case of Marmara Sea, Turkey

Sea food is a major source of animal protein. Marine foods are very rich sources of mineral components. The total content of minerals in the raw flesh of marine fish and invertebrates is in the range of 0.6–1.5% wet weight. The contents of Na, K, Ca, Mg and P are up to 1 mg/100 g, whereas those of Fe, Zn, I are less than 1 mg/100 g. Mussels (Mytilus galloprovincialis) were investigated for macro and trace element composition throughout the year. Ranges of moisture, ash, protein and fat contents were 79.76–87.46 g/100 g, 1.06–2.06 g/100 g, 7.28–12.65 g/100 g and 0.33–3.49 g/100 g, respectively. While the highest protein and fat values were found in the summer (July–August), the highest moisture and ash contents were found in the winter (December–January). The contents of highest Na, K, Ca were found in the summer. Cadmium, lead and copper were found to be below the legislative limits throughout year. High levels of mercury were found in January and October. It should be discussed whether mussel may provide an alternative source of mineral for healthy nutrition.