Thermal and pH stability of Justicia spicigera (Mexican honeysuckle) pigments: Application of mathematical probabilistic models to predict pigments stability.

Kinetic and probabilistic (Time-to-Failure, TTF) models were used to predict the color (L*, a*, b* total color differences (ΔE), Hue and Chroma) stability of Justicia spicigera leaves pigments subjected to different temperatures (40 - 80 °C) and pHs (2 - 12). The change in pH caused different hues (from 60° = orange red to 268° = deep-blue) due to the shift effect of anthocyanins in the extract. Temperatures higher than 60 °C increased the color degradation. High heat sensitivity was observed at pH 4 (Ea = 90.27) and 10 (Ea = 154.99 kJ/mol). The Time-to-Failure model for both ΔE and Hue describes the effect of pH and temperature in the J. spicigera extracts. High pHs and temperatures applied to the extracts increased the probability of showing ΔEs > 4 or Hue changes over 20 %. Nearby the neutral region of pH, pigments of J. spicigera were more stable. The TTF model might be a useful tool to describe and predict the behavior of pigments added to foods.

Microencapsulates by spray of Lacticaseibacillus rhamnosus GG from fermented whole or skimmed cow's milk added with Mexican honeysuckle (Justicia spicigera) extract using mesquite gum as carrier agent.

This work aimed to evaluate the effect of the addition 5°Bx Mexican honeysuckle (Justicia spicigera) extract (JSE) in spray dried encapsulates of whole and skimmed unfermented and fermented cow's milk with Lacticaseibacillus rhamnosus (LR). All samples were spray dried at 160 °C. Samples were analyzed in physical properties (moisture content, water activity (a w ), L∗, a∗, b∗, Hue, Chroma color parameters, particle size), LR content, and bioactive compounds (total anthocyanins (TA), total phenolic content (TPC), and antioxidant capacity (AC) using the DPPH assay). Results showed that the load of LR was in the range 6.79-7.44 Log10 (CFU/mL) cycles after fermentation, lower values were obtained when JSE was added before fermentation. In addition, LR remains after drying in fermented samples but decrease about 1 Log10 (CFU/mL) cycle. LR was 4.46 Log10 (CFU/mL) in the fermented skimmed milk-J. spicigera extract powder. All powders had a w and moisture content below 0.295 and 6.51%, respectively. Color of powders depended on the moment of addition of JSE and fermentation. Powders from fermented milk were pale brownish/orangey/red (Hue = 44.91-59.7) and unfermented and J. spicigera extract-maltodextrin solution (12% w/v) powders were purple (Hue = 314.52-326.68). Higher particle sizes (52.3-104.7 µm) were obtained with whole milk fermented and unfermented powders. On the contrary, skimmed milk and JSE without milk protein had values in the range 15.56-44.0 µm. TPC in powders were higher (16.96-33.81 mg GAE/g powder db) compared with TA (0.27-0.64 mg Peonidin-3,5-diglucoside/g powder db). TPC increased with fermentation and remain after spray drying. The AC and TPCs were highly correlated and had antioxidant capacity of 10.18 mg TE/g powder db. The principal component analysis showed that the type of milk and fermentation separate the powders in four groups, depending on their physical and antioxidant properties. Encapsulated pigments could be used in formulations in the food industry to increase bioactive compounds and pigments in foods.