Proteolytic properties of Turkish white‐brined cheese (Beyaz peynir) made by using wild‐type Lactococcal strains

The development of proteolysis in white‐brined Turkish cheese made by using wild strains of Lactococcus lactis subsp. lactis (namely MBLL9, MBLL23 and MBL27) was monitored for 90 days. Proteolysis in cheeses was investigated using urea‐PAGE gel electrophoresis of pH 4.6‐insoluble and RP‐HPLC of both 70% ethanol‐insoluble and 70% ethanol‐soluble nitrogen fractions. Results indicated that developments of proteolysis in the experimental cheeses were strain dependent. The degradation of casein fractions was more evident in the cheeses made using strain MBLL23. The lowest levels of proteolysis and development of acidity were obtained in the cheese made using strain MBLL9.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Changes in Hydrogen Sulfide and Sulfhydryl Content of Heated Beef Adipose Tissue

SUMMARY— Beef adipose tissue was separated into the water soluble, salt soluble and insoluble (water-salt-ether) fractions, and the amount of H, S evolved upon heating each of the fractions was determined. The yield of H, S per 100 g of adipose tissue was 17.6, 1.7 and 5.5 μM for the water soluble, salt soluble and insoluble fractions, respectively. Thus, the water soluble fraction contributed about 71% of the H, S, while the corresponding contributions from the salt soluble and the insoluble fractions amounted to approximately 7 and 22%, respectively.     

Colloidal calcium phosphates in casein micelles studied by slow-speed-spinning 31P magic angle spinning solid-state nuclear magnetic resonance.

The composition of bovine casein micelles was analyzed by 31P magic angle spinning solid-state nuclear magnetic resonance spectroscopy. By looking at isotropic and anisotropic 31P chemical shift parameters, resonance line shapes, the combination of single-pulse and 1H to 31P cross-polarization spectra, and comparison with spectra for various model compounds combined with multiple-component simulation and iterative fitting procedures, we were able to identify and quantify a variety of inorganic and organic phosphates in the micelles. These include phosphates from mobile and immobile inorganic hydroxyapatite-type phosphates as well as phosphates from kappa-casein and the Ca2+-binding phosphoserines from alphas1-, alphas2-, and beta-casein. This information is discussed in relation to previous knowledge and various models for the colloid formation.     

Identification of gas‐producing components in different varieties of Phaseolus vulgaris by in vitro fermentation

Phaseolus vulgaris consumption has been limited as part of the occidental diet owing to flatulence production. Raffinose, stachyose and verbascose have been shown to be the main components responsible for flatulence; however, it is thought that soluble fibre could also be involved in this phenomenon. The aim of the present study was to identify the main components of beans influencing flatus. Ten varieties of P vulgaris originating from South America were first analysed for their main nutrient and carbohydrate fractions. Three of the varieties were then fractionated to extract soluble and insoluble fibres. Various combinations of α‐galactosides and soluble and insoluble fibre fractions, in similar proportions to those contained in cooked grains, were used as substrates for in vitro fermentation studies using human faecal inoculum to determine the fermentative capacity of each of the three fractions. Considering the white varieties, total gas production and acidification of the medium were correlated with fermented organic matter from soluble fibre (R² = 1)) and with α‐galactosides (R² = 0.75). On the other hand, tannins present in pigmented varieties did not seem to interfere significantly in fermentation of soluble fibre. The total production of gas per gram of mixed fractions of soluble fibre and α‐galactosides in proportions found in cooked grains was lower than that expected from each substrate separately. It can be concluded that soluble fibre and α‐galactosides are good substrates for endogenous colonic flora subjected to in vitro fermentation studies and are thus responsible for flatulence induced by legume consumption. © 2001 Society of Chemical Industry     

Sodium benzoate and potassium sorbate preservatives in food stuffs in Iran

A high-performance liquid chromatography method was applied for the determination of the levels of benzoate and sorbate in 400 food samples, including pickled cucumbers, canned tomato pastes, sour cherry jams, soft drinks, fruit juices and dairy products (UF-Feta cheeses, Lighvan cheeses, lactic cheeses, yogurts and doogh). The results showed that 270 (67.5%) of all samples contained benzoate ranging from 11.9 to 288.5 mg kg^?1 in lactic cheese and fruit juice, respectively. The levels of sorbate in 98 (24.5%) of the samples were 20.1 to 284.3 mg kg^?1 in doogh and fruit juice, respectively. Moreover, benzoate was detected in all dairy products ranging from 11.9 mg kg^?1 in lactic cheese to 91.2 mg kg^?1 in UF-Feta cheese. A low concentration of benzoate could originate naturally, due to specific biochemical mechanisms during cheese, yogurt and doogh maturation. In conclusion, a minimum level for benzoate in dairy products should be defined in the legislation.     

The effect of ripening and cooking temperatures on proteolysis and lipolysis in Manchego cheese

The influence of ripening temperature on proteolysis and lipolysis was studied on four lots of raw ewe's milk Manchego cheese held for 60 days at 5, 10, 15 or 20°C. Mean levels of pH 4·6, trichloroacetic acid and phosphotungstic acid soluble N in 20°C cheeses were 52%, 78% and 95% higher than the respective levels in 5°C cheeses at the end of the ripening period. Free fatty acids content after 60 days was 90% higher in 20°C cheeses than in 5°C cheeses. Significant effects of the cooking temperature of the curd (30, 36, 38 or 40°C) on pH, moisture and NaCl content were recorded, but levels of nitrogenous fractions or free fatty acids in 60-day cheeses were not affected.     

Using High-Pressure Processing for Reduction of Proteolysis and Prevention of Over-ripening of Raw Milk Cheese

High-pressure-processing (HPP) at 400 or 600 MPa was applied to cheeses made from ewe raw milk, on days 21 or 35 after manufacturing, to reduce proteolysis and prevent over-ripening. The characteristics of HPP and non-pressurized (control) cheeses were compared during ripening at 8 °C until day 60 and further storage at 4 °C until day 240. HPP and control cheeses showed similar pH values throughout ripening, but on day 240 pH values remained 0.4–0.6 units lower for HPP cheeses than for the control cheeses. Casein degradation was significantly retarded in the 600 MPa cheeses. Their α-casein concentration was 48–52 % higher on day 60 and 30–33 % higher on day 240 than in the control cheeses while β-casein concentration was 25–26 % higher on day 60 and 100–103 % higher on day 240. No significant differences in para-κ-casein concentration between cheeses were found on day 60, but on day 240, it was 22–35 % higher in the 600 MPa cheeses than in the control cheese. Hydrophilic peptides, hydrophobic peptides and total free amino acids evolved similarly in HPP and control cheeses during the 60-day ripening period. However, on day 240 hydrophilic peptides were at 34–39 % lower levels in the 600 MPa cheeses than in the control cheeses, hydrophobic peptides at 7–16 % lower levels and total free amino acids at 25–29 % lower levels. Flavour intensity scores increased at a slower rate in HPP cheeses than in the control cheese. Flavour quality declined markedly in the control cheeses during refrigerated storage while it did not vary significantly in 600 MPa cheeses.     

Effect of technological parameters on the characteristics of kasseri cheese made from raw or pasteurized ewes' milk

Two groups of kasseri cheese (pasta filata type) were manufactured from raw or pasteurized ewes' milk, without starter cultures. Cheeses of each group were divided into two subgroups: the first was ripened and stored at 4°C and packaged in plastic film; the second ripened and stored at 15°C and coated with paraffin wax. Milk pasteurization and technological parameters had a significant effect on the pH ( P  < 0.05), while only technological parameters had an effect on the total solids content. At day 120, the range of mean cfu/g counts for the mesophilic aerobic flora was 9.5 × 10⁷−1.4 × 10⁸; for the thermophilic streptococci, the range was 2.6 × 10⁷−7.6 × 10⁷; and for the thermophilic bacilli, 9.8 × 10⁶−1.7 × 10⁷. Changes in the N fractions became significant after 30 days of ripening. For mature 120-day-old cheeses, the percentage of total N soluble at pH 4.6 was 22.7%–22.9% in raw milk cheeses and 19.0%–21.7% in pasteurized milk cheeses. The percentage of total N soluble at 12% TCA was 10.1%–12.2% in raw milk cheeses and 7.3%–11.5% in pasteurized milk cheeses; the percentages of total N soluble at 5% PTA were 3.1%–4.0% and 2.6%–3.6%, respectively. The residual α_s-casein percentages at day 120 ranged between 63% and 78% of the respective area at day 1; the residual β-casein ranged between 67% and 75%. There were some characteristic differences in the reverse phase-HPLC peptide profiles of the four cheeses. In general, the effect of the different ripening conditions was more pronounced in cheeses made from pasteurized milk.     

Studies on the ripening of stilton cheese: Proteolysis

The pH of fresh Stilton curd, which 2 h after coagulation was ∼6·7, decreased to ∼4·8 in 4 day-old cheeses but increased gradually thereafter to ∼6 at the end of ripening (70 days). At the end of the normal ripening period, ∼60% of the total N (TN) was water soluble (WSN) and ∼58% of the WSN was soluble in 70% ethanol, while 40% was diffusible on dialysis against water; free amino acid N (phosphotungstic acid-soluble, PTA-N) reached ∼4·8% of TN. The levels of TNBS-reactive amino groups were highly correlated with the values of WSN and 12% TCA-N but showed a greater change in the PTA extract than the value of PTA-N. Dialysable WSN was resolved into five peptide fractions by chromatography on Sephadex G-10; these fractions were very heterogeneous and contained up to eight ninhydrin-positive peptides when examined by TLC. Chromatography on DEAE cellulose revealed a high level of heterogeneity in the 70% ethanol-soluble and -insoluble fractions and this was confirmed by the wide range of N-terminal groups. The free amino acids (FAA, as measured by ion exchange chromatography) represented 6·8% and 9·9% of TN in the 70 day-old experimental cheeses and in commercial samples, respectively. Valine, leucine, lysine and glutamic acid accounted for ∼50% of total FAA throughout the ripening period.     

Prediction of postharvest dry matter, soluble solids content, firmness and acidity in apples (cv. Elshof) using NMR and NIR spectroscopy: a comparative study

Dry matter (DM), soluble solids content (SSC), firmness and acidity by proton nuclear magnetic resonance (NMR) T₂ relaxometry and near infrared (NIR) spectroscopy were investigated on a total of 390 apples (cv. Elshof). The fruit came from four different pre- or postharvest treatments and covered a large range of DM (11.4–20.0 %) and SSC values (10.5–18.3 °Brix). NIR was superior in predicting DM (R ² = 0.82) and SSC (R ² = 0.80), compared to NMR (R ² = 0.50 and R ² = 0.58). However, NMR relaxometry was able to detect multiple water populations assigned to different water pools in the apples and variation in the water distribution between different pre- and postharvest treatments. Differences in the mobility of the vacuole water (population T₂₄) were consistent with changes in fruit firmness. In conclusion, even though NIR is superior in predicting DM and SSC, NMR provides useful information about the intrinsic water state and its distribution in the fruit.     

Chemical and nutritional properties of different fractions of <Emphasis Type="Italic">Prosopis alba</Emphasis> pods and seeds

The objective of this work was to study chemical and nutritional aspects of different fractions of Prosopis alba. Flours from whole pod, pericarp (pulp) and seeds were obtained. Polyphenols were mainly located in pulp but antioxidant activity was higher in whole pod flour and seeds. In seeds, the fraction with the highest polyphenols and antioxidant activity was the seed coat or testa. Protein content was higher in whole pod flour (5.81 %) than in pulp flour (3.52 %), presenting the seed an appreciable amount 33.6 %. These proteins were composed by monomer subunits of 85, 67, 38, 16 and 14 kDa and no prolamins and anti-tryptic activity were detected. P. alba flours presented high content of soluble sugars, mainly composed by sucrose, and also high amount of insoluble dietary fiber. The major mineral was potassium. The whole pod, due to the contribution of seeds, contained high amount of calcium, magnesium, iron and zinc, all indispensable minerals for human nutrition. Therefore, P. alba flours, mainly containing the seeds, constitute nutritional ingredients for bakery and gluten free products.     

Changes in Size and Composition of Protein Aggregates on Heating Reconstituted Concentrated Skim Milk at 120oC

Treatment at 120^oC caused initial transfer of protein from the serum and small micelle fraction to the medium-sized micelle fraction. More extensive heating caused transfer of protein from the medium fraction to the large-sized micelle fraction, and the serum fraction as 'soluble’casein. Protein composition of large-sized micelle fraction remained essentially constant, but for the other fractions it changed throughout the heating period. Experiments with heated milks that had been made free of colloidal calcium phosphate (CCP) showed that a proportion of the calcium phosphate in milk, whether indigenous or precipitated by heating, became less soluble. This‘insoluble’calcium phosphate was possibly involved in joining the smaller protein particles into larger-sized aggregates.     

Proteolysis texture and microstructure of low‐fat Tulum cheese affected by exopolysaccharide‐producing cultures during ripening

The objective of the study was to determine the effects of exopolysaccharide (EPS)‐producing or non‐EPS‐producing starters on proteolysis, physical and microstructural characteristics of full‐fat or low‐fat Tulum cheeses during ripening. For this purpose, Tulum cheese was manufactured using full‐ or low‐fat milk with EPS‐producing and non‐EPS‐producing starter cultures. Chemical composition, proteolysis, texture profiles and microstructure of the cheeses were studied during 90 days of ripening. Urea‐PAGE of water‐insoluble and RP‐HPLC peptide profiles of water‐soluble fractions of the cheeses showed that the use of starters resulted in different degradation patterns in all cheeses during ripening. Although β‐casein exhibited similar degradation patterns in all cheeses, small differences are present in α_s1‐casein degradation during ripening. Reducing fat in Tulum cheese changed the RP‐HPLC peptide profile of the cheeses. The use of EPS‐producing cultures improved the textural characteristics and changed the microstructure and proteolysis of low‐fat Tulum cheese.     

Fractionation of water insoluble solids and extraction of pectins from residues of juice-extracted satsuma mandarin fruit by wet grinding

The waste biomass residue from satsuma mandarin juice production was extracted by wet-fine grinding and separated by centrifugation into insoluble and soluble fractions. The insoluble material was wet-screened into four fractions and analysed for crude fibre and total hydrolysable sugars. Crude fibre was almost exclusively in fractions containing particles over 50 μm, comprising about 65% of the insoluble material; this could provide a raw material high in crude fibre. The remaining insoluble fraction was almost devoid of crude fibre.
The soluble extract contained up to 63% of the total pectic substances with very similar methoxyl contents and degree of esterification, but double the viscometric molecular weight of a standard citrus pectin. The method provides an alternative to that of hot acid extraction.     

Nutritional and functional performance of high β-glucan barley flours in breadmaking: mixed breads versus wheat breads

The ability of high β-glucan barley (HBGB) flour versus regular commercial barley (CB) to make highly nutritious wheat (WT) blended breads meeting functional and sensory standards has been investigated. Mixed breads obtained by 40 % replacement of WT flour by HBGB flours are more nutritious than those replaced by CB flours and much more than regular WT flour breads in terms of elevated levels of dietary fibre fractions (soluble, insoluble, resistant starch and β-glucans), slowly digestible starch subfraction and bioaccessible polyphenols providing higher antiradical activity. WT/CB and WT/HBGB breads can be, respectively, labelled as source of fibre (3 g DF/100 g food) and high-fibre breads (6 g DF/100 g food), according to Nutritional Claims for dietary fibre foods. The consumption of 100 g of WT/HBGB can meet up to almost 50 % the required dietary fibre, providing a β-glucan intake high enough to meet the requirements of the EFSA health claim (3 g/day), contributing a reduced blood cholesterol level. The techno-functional performance of fresh blended breads and the sensory appreciation were in general preserved or even improved.     

Influence of starters on chemical, biochemical, and sensory changes in Turkish White-brined cheese during ripening

Turkish White-brined cheese was manufactured using Lactococcus strains (Lactococcus lactis ssp. lactis NCDO763 plus L. lactis ssp. cremoris SK11 and L. lactis ssp. lactis UC317 plus L. lactis ssp. cremoris HP) or without a starter culture, and ripened for 90 d. It was found that the use of starters significantly influenced the physical, chemical, biochemical, and sensory properties of the cheeses. Chemical composition, pH, and sensory properties of cheeses made with starter were not affected by the different starter bacteria. The levels of soluble nitrogen fractions and urea-PAGE of the pH 4.6-insoluble fractions were found to be significantly different at various stages of ripening. Urea-PAGE patterns of the pH 4.6-insoluble fractions of the cheeses showed that considerable degradation of α_s1-casein occurred and that β-casein was more resistant to hydrolysis. The use of a starter culture significantly influenced the levels of 12% trichloroacetic acid-soluble nitrogen, 5% phosphotungstic acid-soluble nitrogen, free amino acids, total free fatty acids, and the peptide profiles (reverse phase-HPLC) of 70% (vol/vol) ethanol-soluble and insoluble fractions of the pH 4.6-soluble fraction of the cheeses. The levels of peptides in the cheeses increased during the ripening period. Principal component and hierarchical cluster analyses of electrophoretic and chromatographic results indicated that the cheeses were significantly different in terms of their peptide profiles and they were grouped based on the use and type of starter and stage of ripening. Levels of free amino acid in the cheeses differed; Leu, Glu, Phe, Lys, and Val were the most abundant amino acids. Nitrogen fractions, total free amino acids, total free fatty acids, and the levels of peptides resolved by reverse phase-HPLC increased during ripening. No significant differences were found between the sensory properties of cheeses made using a starter, but the cheese made without starter received lower scores than the cheeses made using a starter. It was found that the cheese made with strains NCDO763 plus SK11 had the best quality during ripening. It was concluded that the use of different starter bacteria caused significant differences in the quality of the cheese, and that each starter culture contributed to proteolysis to a different degree.     

Indigestible fraction of okara from soybean: composition,physicochemical properties and in vitro fermentability by pure cultures of <Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis> and <Emphasis Type="Italic">Bifidobacterium bifidum</Emphasis>

Major non-digestible components of soybean seeds and okara were determined by an in vitro enzymatic-physiological method, alternative to dietary fibre. Total indigestible fraction was higher in okara (41.6%) than in seeds (28.5%), and consisted of soluble and insoluble fractions, mainly composed of non-starch polysaccharides, klason lignin and resistant protein. Total protein was lower in okara (32.29%) than in seeds (46.97%), as were oil (14.72% okara–20.89% seeds) and ash contents (3.18% okara–4.60% seeds). In vitro digestibility of protein was lower for okara (84.3%), than for soybean seed (91.8%). Moreover, okara showed high swelling (10.54 ± 0.14 mL/g d.w.) and water retention capacity (8.87 ± 0.06 g/g d.w.) and was fermented in vitro to a greater extent by Bifidobacterium bifidum (29.8%), than by Lactobacillus acidophilus (8.3%). For its composition, physico-chemical properties and bifidogenic capacity in vitro, okara is a potential candidate to be a prebiotic fibre-rich ingredient of new functional foods.     

Inclusion of starch in imitation cheese: Its influence on water mobility and cheese functionality

The impact of starch type and concentration on the nature of water in and the rheology of imitation cheese were investigated. Imitation cheese (55% moisture) containing four starches (native, pre-gelatinised, resistant or waxy corn) at inclusion levels of 1.9%, 3.9%, 5.8%, 7.8%, or 9.9% w/w were manufactured using a Brabender Farinograph-E^®. The textural properties were assessed by torsion gelometry and dynamic rheology and the mobility of water by nuclear magnetic resonance (NMR) relaxation techniques. Cheese microstructure was assessed using light microscopy. Increasing the starch content changed the texture of cheeses from ‘soft’ to ‘brittle/tough’ and significantly (p<0.05) decreased the mobility of water. Cheese melt and hardness were influenced by the mobility of water. Matrices in which the water was more mobile produced good melting soft cheeses, while cheeses in which water was less mobile were tough and non-melting. Light micrographs showed that starch type influenced cheese microstructure. The native and pre-gelatinised starches became swollen and disrupted the continuity of the protein matrix, separating the matrix into a protein and starch phase. Resistant and waxy corn starches were present in the protein matrix as small discrete particles, appearing relatively intact, unswollen and relatively unchanged by the cheese manufacturing process. The study indicates that varying the level/type of starch alters the water mobility and thus the functionality of imitation cheeses.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on cheddar cheese quality: pH changes during ripening

The pH of cheese is an important attribute that influences its quality. Substantial changes in cheese pH are often observed during ripening. A combined effect of calcium, phosphorus, residual lactose, and salt-to-moisture ratio (S/M) of the cheese on the changes in cheese pH during ripening was investigated. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. All the cheeses were salted at a pH of 5.4, pressed for 5 h, and then ripened at 6 to 8°C. The pH of the salted curds before pressing and the cheeses during 48 wk of ripening was measured. Also, cheeses were analyzed for water-soluble Ca and P, organic P, and bound inorganic P during ripening. Changes in organic acids’ concentration and shifts in the distribution of Ca and P between different forms were studied in relation to changes in pH. Cheeses with low S/M exhibited a larger increase in acid production during ripening compared with high S/M cheeses. Cheeses with the highest concentration of bound inorganic P exhibited the highest pH, whereas cheeses with the lowest concentration of bound inorganic P exhibited the lowest pH among the 8 treatments. Although conversion of lactose to short-chain, water-soluble organic acids decreased cheese pH, bound inorganic phosphate buffered the changes in cheese pH. Production of acid in excess of the buffering capacity (which was the case in low Ca and P and low S/M treatments) led to a low pH, whereas solubilization of bound inorganic P in excess to acid production (which was the case in high Ca and P and high S/M treatments) led to an increase in pH. However, for cheeses with high Ca and P and low S/M, changes in cheese pH were influenced by the level of residual lactose. Hence, pH changes in Cheddar cheese can be modulated by a concomitant control on the amount and state of Ca and P, level of residual lactose, and S/M of the cheese.