ESTIMATION OF LIPASE IN DAIRY PRODUCTS: II. AN EXTRACTION–TITRATION METHOD FOR THE ESTIMATION OF BACTERIAL LIPASE

1949 ◽  
Vol 27f (12) ◽  
pp. 491-498 ◽  
Author(s):  
D. J. Lubert ◽  
L. M. Smith ◽  
H. R. Thornton
Keyword(s):  
Lipase Activity ◽  
Dairy Products ◽  
Skim Milk ◽  
Reaction Medium ◽  
Ether Extract ◽  
Titration Method ◽  
Wide Ph Range ◽  
Ph Range

A method of estimating bacterial lipase is presented that is believed to be more nearly quantitative than any other at present available. The method is based on the titration of acids in an ether extract of a skim milk culture to following a 30 mm period of lipase activity at 37 °C. It is shown that ether-soluble acids carried into the reaction medium do not interfere with the measurements and that ether-soluble acids are not produced from protein or lactose during the test. The method is applicable over a sufficiently wide pH range to make it generally adaptable in bacteriology.

ESTIMATION OF LIPASE IN DAIRY PRODUCTS: I. AN EXTRACTION-TITRATION METHOD FOR THE ESTIMATION OF MILK LIPASE

1949 ◽  
Vol 27f (12) ◽  
pp. 483-490 ◽  
Author(s):  
L. M. Smith ◽  
D. J. Lubert ◽  
H. R. Thornton
Keyword(s):  
Enzymatic Hydrolysis ◽  
Butyric Acid ◽  
Lipase Activity ◽  
Dairy Products ◽  
Ether Extract ◽  
Titration Method ◽  
Micro Organisms ◽  
Hydrolysis Of

A procedure has been outlined for the estimation of milk lipase. The method is based on the titration of an ether extract of butyric acid derived from the enzymatic hydrolysis of tributyrin under standardized conditions. Some of the fundamental factors involved in the procedure have been discussed. It is suggested that modifications of the method may be used to study lipase activity in other dairy products and in cultures of micro-organisms.

ESTIMATION OF LIPASE IN DAIRY PRODUCTS: III. LIPASE ACTIVITY IN CULTURES OF MICRO-ORGANISMS AND IN CHEESE

1949 ◽  
Vol 27f (12) ◽  
pp. 499-503 ◽  
Author(s):  
D. J. Lubert ◽  
L. M. Smith ◽  
H. R. Thornton
Keyword(s):  
Lipase Activity ◽  
Dairy Products ◽  
Lipolytic Activity ◽  
Skim Milk ◽  
Preceding Paper ◽  
Cheddar Cheese ◽  
Titration Method ◽  
Number Of Species ◽  
The One ◽  
Micro Organisms

The lipolytic activity in skim milk cultures of micro-organisms representing a number of species and genera were studied by the extraction–titration method described in the preceding paper. No evidence was found of a bacterial lipase having an activity optimum on the acid side of neutrality. No lipase active at approximately pH 5.0 was demonstrated in 20 samples of commercial cheddar cheese of varying age or one sample of blue veined cheese on measurement by the extraction–titration method or by the Peterson et al. method. Weak lipolytic activity was found in one sample of blue veined cheese by the extraction–titration method. No lipolytic activity at pH 8.5 was demonstrated by the extraction–titration method in the one sample of cheese tested at this pH.

ESTIMATION OF LIPASE IN DAIRY PRODUCTS: IV. LIPOLYTIC ACTIVITY OF PSEUDOMONAS FLUORESCENS

1949 ◽  
Vol 27f (12) ◽  
pp. 504-509 ◽  
Author(s):  
D. J. Lubert ◽  
L. M. Smith ◽  
H. R. Thornton
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Fluorescens ◽  
Calcium Chloride ◽  
Dairy Products ◽  
Lipolytic Activity ◽  
Skim Milk ◽  
Reaction Medium ◽  
Nutrient Broth ◽  
Optimum Ph ◽  
Coli Growth

The lipolytic activity of a strain of Pseudomonas fluorescens was investigated. Under the investigational conditions activity was greatest when the reaction medium was at approximately pH 8.9 at the start of the reaction period and when the reaction was carried out at approximately 42 °C. The optimum pH for activity by this enzyme was found to be between 8 and 9. This lipase is not specific for tributyrin but hydrolyzes tricaproin and tricaprylin as well, although with decreasing ease. Calcium chloride inhibited rather than enhanced the activity. Lipolytic activity was greater in nutrient broth-base media than in skim milk but the latter was more satisfactory with which to work. Lypolytic activity and fluorescence were not found to be related. Nutrient broth freed of carbohydrate by Escherichia coli growth and heat-sterilized stimulated production of fluorescence.

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

High degradation efficiency of sulfamethazine with the dual-reaction-center Fe-Mn-SiO2 Fenton-like nanocatalyst in a wide pH range

2021 ◽  
Author(s):  
Manoj Kumar Panjwani ◽  
Qing Wang ◽  
Yueming Ma ◽  
Yuxuan Lin ◽  
Feng Xiao ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Reaction Center ◽  
Degradation Efficiency ◽  
Heterogeneous Fenton ◽  
Wide Ph Range ◽  
Ph Range

The development of a heterogeneous Fenton-like catalyst, possessing high degradation efficiency in a wide pH range, is crucial for wastewater treatment. The Fe-Mn-SiO2 catalyst was designed, and prepared by a...

scholarly journals Using a B-Phycoerythrin Extract as a Natural Colorant: Application in Milk-Based Products

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 297
Author(s):  
Ana Belén García ◽  
Eleonora Longo ◽  
Mª Carmen Murillo ◽  
Ruperto Bermejo
Keyword(s):  
Cold Storage ◽  
Dairy Products ◽  
Color Stability ◽  
Good Stability ◽  
Natural Food ◽  
Natural Colorant ◽  
Natural Origin ◽  
Short Period ◽  
Food Dyes ◽  
Ph Range

Nowadays, there is a growing interest in finding new coloring molecules of natural origin that can increase and diversify the offer of natural food dyes already present in the market. In the present work, a B-phycoerythrin extract from the microalgae Porphyridium cruentum was tested as a food colorant in milk-based products. Using spectroscopy and colorimetry, the extract was characterized and gave evidence of good properties and good stability in the pH range between 4.0 and 9.0. Coloring studies were conducted to demonstrate that samples carrying the pink extract could be used for simulating the pink color of marketed milk-based products. The staining factors, representing the amount of pink protein to be added to reproduce the color of strawberry commercial products, ranged between 1.6 mg/L and 49.5 mg/L, being sufficiently low in all samples. Additionally, color stability during a short period of cold storage was studied: it demonstrated that the three tested types of dairy products remained stable throughout the 11-day analysis period with no significant changes. These results prove the potential of the B-phycoerythrin extract as a natural colorant and alternative ingredient to synthetic coloring molecules.

scholarly journals Defect-Rich Heterogeneous MoS2/rGO/NiS Nanocomposite for Efficient pH-Universal Hydrogen Evolution

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 662 ◽  
Author(s):  
Guangsheng Liu ◽  
Kunyapat Thummavichai ◽  
Xuefeng Lv ◽  
Wenting Chen ◽  
Tingjun Lin ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Active Sites ◽  
Reduced Graphene ◽  
Heterogeneous Interfaces ◽  
Wide Ph Range ◽  
Ph Range ◽  
A Current ◽  
Poor Stability

Molybdenum disulfide (MoS2) has been universally demonstrated to be an effective electrocatalytic catalyst for hydrogen evolution reaction (HER). However, the low conductivity, few active sites and poor stability of MoS2-based electrocatalysts hinder its hydrogen evolution performance in a wide pH range. The introduction of other metal phases and carbon materials can create rich interfaces and defects to enhance the activity and stability of the catalyst. Herein, a new defect-rich heterogeneous ternary nanocomposite consisted of MoS2, NiS and reduced graphene oxide (rGO) are synthesized using ultrathin αNi(OH)2 nanowires as the nickel source. The MoS2/rGO/NiS-5 of optimal formulation in 0.5 M H2SO4, 1.0 M KOH and 1.0 M PBS only requires 152, 169 and 209 mV of overpotential to achieve a current density of 10 mA cm−2 (denoted as η10), respectively. The excellent HER performance of the MoS2/rGO/NiS-5 electrocatalyst can be ascribed to the synergistic effect of abundant heterogeneous interfaces in MoS2/rGO/NiS, expanded interlayer spacings, and the addition of high conductivity graphene oxide. The method reported here can provide a new idea for catalyst with Ni-Mo heterojunction, pH-universal and inexpensive hydrogen evolution reaction electrocatalyst.

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