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 ±â€¯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 ±â€¯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 ±â€¯5.29 U/mL, a specific milk-clotting activity (SMCA) of 9950.17 ±â€¯220.74 U/mg, and an SMCA/PA ratio of 1124.31 ±â€¯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.

Effects of processing on the chemical, physicochemical, enzymatic, and volatile metabolic composition of pitaya (Hylocereus polyrhizus (F.A.C. Weber) Britton & Rose).

The effects of processing on the chemical, physicochemical, enzymatic, and volatile metabolic composition of pitaya pulp were assessed for the first time. To this end, the following treatments to obtain pitaya pulp were evaluated: Treatment A (TA, pulp processing without ascorbic acid), Treatment B (TB, whole fruit processing with ascorbic acid), and Control (whole fruit processing without ascorbic acid). The treatment employed in TB resulted in low polyphenol oxidase and peroxidase activity, and no significant chemical or physicochemical alterations in most parameters evaluated. In addition, TB presents high yields and fiber content compared to the TA or Control. For metabolic analysis, Gas Chromatography-Mass Spectrometry (GC-MS) was effective for the simultaneous determination of 80 volatile metabolites in pitaya. Chemometric analyses was used to efficiently distinguish the volatile compounds of each treatment, and demonstrated that TB presents an interesting volatile profile due the conservation or agregation of compounds.

Optimization of headspace solid phase micro-extraction of volatile compounds from papaya fruit assisted by GC-olfactometry.

Optimization of the extraction conditions to investigate the volatile composition of papaya fruit involving headspace solid phase micro-extraction was carried out using multivariate strategies such as factorial design and response surface methodology. The performance of different combinations of time for reaching the equilibrium in the headspace and time for maximum extraction of volatiles was evaluated by GC-olfactometry of the extract (intensity of papaya characteristic aroma), number of peaks and total area in the chromatogram. Thirty-two compounds were identified by GC-MS under the optimized extraction conditions, the majority of which were aldehydes, both in number of compounds and area. Major compounds were δ-octalactone, ß-citral, benzaldehyde, heptanal, benzyl isothiocyanate, isoamyl acetate, γ-octalactone, (E)-linalool oxide and benzyl alcohol. Seven aldehydes and two other compounds are reported for the first time in papaya's volatile profile.