Insights into milk-clotting activity of latex peptidases from Calotropis procera and Cryptostegia grandiflora

New Coagulant Proteases for Cheesemaking from Leaves and Latex of the Spontaneous Plant Pergularia tomentosa: Biochemical Characterization of Coagulants and Sensorial Evaluation of Cheese

The purpose of this study was to evaluate the caseinolytic and milk-clotting activities of aqueous crude extracts from leaves and latex of the Pergularia tomentosa, to determine their suitability as a rennet substitute. These extracts were subjected to a series of biochemical tests before being used in the production of cheese. The results showed that the enzymatic latex extract had a higher coagulant activity than the leaf extract. However, under different clotting conditions (pH, temperature, and CaCl₂ concentration), both coagulants behaved similarly in the coagulation of Berridge substrate. The SDS-PAGE and zymographic analysis revealed identical protein bands with a single active zone in both extracts, corresponding to a molecular weight of 26.98 kDa and 26.03 kDa in the extract of leaf and latex, respectively. Both extracts were stable to different effectors but strongly inhibited by iodoacetamide and Hg, suggesting it to be a cysteine protease. Both extracts were able to hydrolyze casein and generate peptides of 14 kDa, with excessive hydrolysis of the other casein fractions. The physicochemical parameters of cheese made from latex and leaf extract evolved similarly to control cheese. According to the sensory evaluation, cheese made with latex had a mildly bitter flavor but showed a high acceptance rate (>80%).

Processing and preservation methods of Wagashi Gassirè, a traditional cheese produced in Benin

Purpose

Wagashi Gassirè (WG) is a traditional cheese produced from cow milk following local processing methods in Benin. The aim of this study was to describe the milk processing methods and the preservation practices with the objective of improving WG production and sanitary quality.

Methods

A survey was carried out among 390 actors (84 dairy farmers, 165 producers, 53 traders, and 88 consumers) from two municipalities (Dassa and Nikki) in Benin.

Results

WG is highly preferred by consumers for its whiteness (63.0%), softness (24.7%), smoothness (19.2%), and firmness (13.7%). WG production is based on the coagulation of milk using Calotropis procera extracts as coagulant. Six milk processing methods, including three new WG production methods were identified, depending on how the C. procera extracts were pre-treated and used during WG production. Boiling (67%) was the most widely used as WG preservation method. The use of aluminium cooking pots (100% of WG producers), WG open-air production (66.7% of producers) and antibiotic misuse (59.3% of dairy farmers) may lead to the chemical or microbiological contamination of WG.

Conclusions

Six WG production and six preservation methods were identified after the survey among WG producers and traders. Future studies should assess the sanitary and physico-chemical quality of WG from the identified processing and preservation methods. The next step of research should be also focused on the development of specific standards to produce a better quality of WG.

Milk-clotting and hydrolytic activities of an aspartic protease from Salpichroa origanifolia fruits on individual caseins

In recent years, many attempts have been made to find new plant proteases to make artisan cheeses. The global increase in cheese consumption, together with a lower supply and increasing cost of calf rennet, religious factors (Islam and Judaism) and food choices (vegetarianism) have led to the search for suitable rennet substitutes for milk clotting. This study describes the milk-clotting and hydrolytic activities of an aspartic protease from Salpichroa origanifolia fruits (SoAP) on individual caseins to explore its potential use as an alternative to animal rennet. The milk-clotting index obtained for SoAP was 8.4 times lower than that obtained for chymosin. SoAP showed a higher degree of hydrolysis on α-casein than on the other fractions under the proposed conditions. RP-HPLC, mass spectrometry analyses and sequencing of the hydrolysates allowed identifying five peptides from α-casein, one peptide from β-casein, and three peptides from k-casein. In silico analysis showed that the peptides identified may display a wide variety of potential biological activities. These results demonstrate the possibility of using SoAP for the manufacture of new types or artisan cheeses, with the simultaneous added value of the potential health-promoting benefits of the bioactive peptides generated during the hydrolysis.

Extraction, partial purification and characterization of proteases from the red seaweed Gracilaria edulis with similar cleavage sites on κ-casein as calf rennet

Enzymes currently used in cheesemaking have various drawbacks, and there is a continual need to find new coagulants. This study describes the extraction and biochemical characterization of two proteases from the red alga Gracilaria edulis. The proteases were extracted with phosphate buffer and partially purified by ammonium sulphate precipitation and dialysis. The enzymes exhibited optimum caseinolytic activity at 60 °C and a pH range of 6-8. They showed a high ratio of milk-clotting over caseinolytic activity, indicating they had an excellent milk-clotting ability. The proteases were confirmed to be serine protease and metalloprotease with molecular weight (MW) of 44 and 108 kDa. They exhibited high hydrolytic activity on κ-caseins, cleaving κ-casein at four main sites, one of which being the same as that of calf rennet, which is the first reported for an algal protease. The findings demonstrated that the proteases could potentially be used as a milk coagulant in cheesemaking.

Standardized production of a homogeneous latex enzyme source overcoming seasonality and microenvironmental variables

Calotropis procera produces a milky sap containing proteolytic enzymes. At low concentrations, they induce milk-clotting (60 µg/ml) and to dehair hides (0.05 and 0.1%). A protocol for obtaining the enzymes is reported. The latex was mixed with distilled water and the mixture was cleaned through centrifugation. It was dialyzed with distilled water and centrifuged again to recover the soluble fraction [EP]. The dialyze is a key feature of the process. EP was characterized in terms of protein profile, chemical stability, among other criteria. Wild plants belonging to ten geographic regions and grown in different ecological conditions were used as latex source. Collections were carried out, spaced at three-month, according to the seasons at the site of the study. Proteolytic activity was measured as an internal marker and for determining stability of the samples. EP was also analyzed for metal content and microbiology. EP showed similar magnitude of proteolysis, chromatographic and electrophoretic profiles of proteins. Samples stored at 25 °C exhibited reduced solubility (11%) and proteolytic capacity (11%) after six months. Enzyme autolysis was negligible. Microbiological and metal analyses revealed standard quality of all the samples tested. EP induced milk clotting and hide dehairing after storage for up to six months.

Biotechnological potential of a cysteine protease (CpCP3) from Calotropis procera latex for cheesemaking

This article reports the characterization and evaluation of the biotechnological potential of a cysteine protease purified from Calotropis procera (CpCP3). This enzyme was highly stable to different metal ions and was able to hydrolyze κ-casein similarly to bovine chymosin. Atomic force microscopy showed that the process of casein micelle aggregation induced by CpCP3 was similar to that caused by chymosin. The cheeses made using CpCP3 showed higher moisture content than those made with chymosin, but protein, fat, and ash were similar. The sensory analysis showed that cheeses made with CpCP3 had high acceptance index (>80%). In silico analysis predicted the presence of only two short allergenic peptides on the surface of CpCP3, which was highly susceptible to digestive enzymes and did not alter zebrafish embryos' morphology and development. Moreover, recombinant CpCP3 was expressed in Escherichia coli. All results support the biotechnological potential of CpCP3 as an alternative enzyme to chymosin.

Identification, characterization, and antifungal activity of cysteine peptidases from Calotropis procera latex

Cysteine peptidases (EC 3.4.22) are the most abundant enzymes in latex fluids. However, their physiological functions are still poorly understood, mainly related to defense against phytopathogens. The present study reports the cDNA cloning and sequencing of five undescribed cysteine peptidases from Calotropis procera (Aiton) Dryand (Apocynaceae) as well as some in silico analyses. Of these, three cysteine peptidases (CpCP1, CpCP2, and CpCP3) were purified. Their enzymatic kinetics were determined and they were assayed for their efficacy in inhibiting the hyphal growth of phytopathogenic fungi. The mechanism of action was investigated by fluorescence and atomic force microscopy as well as by induction of reactive oxygen species (ROS). The deduced amino acid sequences showed similar biochemical characteristics and high sequence homology with several other papain-like cysteine peptidases. Three-dimensional models showed two typical cysteine peptidase domains (L and R domains), forming a "V-shaped" active site containing the catalytic triad (Cys, His, and Asn). Proteolysis of CpCP1 was higher at pH 7.0, whereas for CpCP2 and CpCP3 it was higher at 7.5. All peptidases exhibited optimum activity at 35 °C and followed Michaelis-Menten kinetics. However, the major difference among them was that CpCP1 exhibited highest V_max, K_m, K_cat and catalytic efficiency. All peptidases were deleterious to the two fungi tested, with IC₅₀ of around 50 μg/mL. The peptidases promoted membrane permeabilization, morphological changes with leakage of cellular content, and induction of ROS in F. oxysporum spores. These results corroborate the hypothesis that latex cysteine peptidases play a role in defense against fungi.

Noni (Morinda citrifolia L.) fruit as a new source of milk-clotting cysteine proteases

This work reports the characterisation of caseinolytic and milk-clotting activities of proteases extracted from ripe fruits of Morinda citrifolia L., as a potential of their use in cheese production. Noni puree extract (NPE) was obtained by homogenising the fresh puree in 150 mM NaCl/50 mM sodium phosphate buffer (pH 7.0). The resulting protein concentration was of 0.367 ± 0.006 mg/mL, and an electrophoretic profile of the extract revealed protein bands ranging from 14 to 55 kDa. The proteolytic activity of NPE was higher when the extract had been previously incubated at pH 6.0 (8.859 ± 0.216 U/mg), whereas the optimum caseinolytic activity was observed at 50 °C. Noni puree proteases were strongly (98%) inhibited by iodoacetamide and E-64, suggesting the presence of only cysteine proteases in the crude extract. NPE proteases showed a milk-clotting activity (MCA) of 238.80 ± 5.29 U/mL, a specific milk-clotting activity (SMCA) of 9950.17 ± 220.74 U/mg, and an SMCA/PA ratio of 1124.31 ± 24.94, this last being comparable to those of commercial calf rennet. The cheese manufactured using NPE presented brittle and soft texture, high humidity, and showed sanitary conditions compatible with current Brazilian regulations. The product showed a slightly bitter taste, but still good acceptability, rating between 6 and 7 in the hedonic scale for flavour, texture, and overall acceptance. Lastly, there was 60% of positive purchase intent, demonstrating that noni fruit is a promising source of milk-clotting enzymes for the dairy industry.

The Formulation of Cheese Analogue from Sweet Corn Extract

Analogue cheese made from sweet corn extract was expected to fulfill the people's need for cheese and as alternative cheese made from cow's milk. The use of maltodextrin as a filler and citric acid as an acidulant was expected to improve the characteristics of corn cheese. The aims of this article were to (1) determine the optimum concentration of maltodextrin, papain, and citric acid in order to produce corn milk-based cheese analogue with the best characteristics; (2) determine the characteristics of cheese analogue produced using the optimum concentration. The research design used in this study was Response Surface Methodology (RSM) based on Central Composite Design (CCD) with three factors: citric acid concentration (0.12%, 0.16%, and 0.20%), commercial papain (0.026%, 0.030%, and 0.034%), and maltodextrin (10%, 15%, and 20%). The optimum formula to produce cheese analogue with the highest protein content and yield was with the addition of 0.20% citric acid, 0.029% papain, and 20% maltodextrin. The cheese analogue produced from the optimum formula had moisture content of 61.590%, yield of 17.512%, total dissolved solids of 19.00°Brix, dissolved protein of 19.837%, acidity (pH) of 5.4, and fat of 6.976%. The sensory characteristics of cheese analogue spread from sweet corn extract are similar to those of cheese from cow's milk; i.e., it had a yellowish-white color, distinctive aroma of cheese, no sour taste, and soft texture and was easy to spread. Therefore, it was possible to explore the sweet corn as ingredient of spread cheese that has low fat content.

Physico-chemical characterization of dairy gel obtained by a proteolytic extract from Calotropis procera - A comparison with chymosin

Chymosin is the major enzyme used in cheesemaking but latex enzymes are also used. The aim of this work was to characterize the composition and the structure of dairy gel obtained by an extract of Calotropis procera leaves in comparison with those obtained by chymosin. The biochemical and mineral compositions of the curds and the cheese yields obtained by using Calotropis procera extract or chymosin were relatively similar. Quantitative and qualitative evaluations of proteolysis after milk coagulation, determined by the non-protein nitrogen content and chromatography coupled to mass spectrometry, indicated that Calotropis procera extract was more proteolytic than chymosin and that κ-casein was proteolyzed. The main consequence of proteolysis by Calotropis procera extract or chymosin was the formation of a similar and regular network with the presence of aggregates of casein micelles. These results support that Calotropis procera extract can be used as effective coagulant in cheesemaking.