Angiotensin I-converting enzyme (ACE) peptides are bioactive peptides that have important value in terms of research and application in the prevention and treatment of hypertension. While widespread literature is concentrated on casein or whey protein for production of ACE-inhibitory peptides, relatively little information is available on selecting the proper proteases to hydrolyze the protein. In this study, skimmed cow and goat milk were hydrolyzed by four commercial proteases, including alkaline protease, trypsin, bromelain, and papain. Angiotensin I-converting enzyme-inhibitory peptides and degree of hydrolysis (DH) of hydrolysates were measured. Moreover, we compared the difference in ACE-inhibitory activity between cow and goat milk. The results indicated that the DH increased with the increase in hydrolysis time. The alkaline protease-treated hydrolysates exhibited the highest DH value and ACE-inhibitory activity. Additionally, the ACE-inhibitory activity of hydrolysates from goat milk was higher than that of cow milk-derived hydrolysates. Therefore, goat milk is a good source to obtain bioactive peptides with ACE-inhibitory activity, as compared with cow milk. A proper enzyme to produce ACE-inhibitory peptides is important for the development of functional milk products and will provide the theoretical basis for industrial production.

Antioxidant peptides are currently the focus of many studies, since they eliminate free radicals in the human body without harmful effects. In the present study, Lactobacillus casei L61 was used as a starter culture to ferment goat milk because of its high capacity to produce antioxidant peptides. An optimal nutrients formula (casein, casein peptone, glucose, soybean peptone, inulin, calcium lactate, and cysteine) was investigated by Plackett–Burman (P–B) and Box–Behnken (B–B) designs for response surface methodology (RSM). Antioxidant peptides were successively isolated and purified from the fermented goat milk. Furthermore, the stability of the antioxidant peptides was evaluated in a simulated gastrointestinal tract at 37 °C. The results showed that calcium lactate, glucose, and casein peptone significantly affected the antioxidant activity of goat milk. The optimal additive amounts were 0.99% (w/v) calcium lactate, 0.21% (w/v) glucose, and 0.29% (w/v) casein peptone. The hydroxyl free radical scavenging rate increased significantly (p < 0.001) from 56.50 ± 0.57% to 88.01 ± 0.69%; the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate increased up to 63.48 ± 1.22% under the optimal conditions (n = 3). Our research provides a fitted mathematical model for antioxidant peptides production. Besides, these antioxidant peptides had great stability during simulated gastrointestinal digestion.

Microencapsulations of Lactobacillus acidophilus in xanthan-chitosan (XC) and xanthan-chitosan-xanthan (XCX) polyelectrolyte complex (PEC) gels were prepared in this study. The process of encapsulation was optimized with the aid of response surface methodology (RSM). The optimum condition was chitosan of 0.68%, xanthan of 0.76%, xanthan-L. acidophilus mixture (XLM)/chitosan of 1:2.56 corresponding to a high viable count (1.31 ± 0.14) × 10¹⁰ CFU·g⁻¹, and encapsulation yield 86 ± 0.99%, respectively. Additionally, the application of a new encapsulation system (XC and XCX) in yoghurt achieved great success in bacterial survival during the storage of 21 d at 4 °C and 25 °C, respectively. Specially, pH and acidity in yogurt were significantly influenced by the new encapsulation system in comparison to free suspension during 21 d storage. Our study provided a potential encapsulation system for probiotic application in dairy product which paving a new way for functional food development.

Food-derived polysaccharides have advantages over synthetical compounds and have attracted interest globally for decades. In this study, we optimized the cellulase-assisted extraction of polysaccharides from white hyacinth bean (PWBs) with the aid of response surface methodology (RSM). The optimum extraction parameters were a pH of 7.79, a cellulase of 2.73%, and a ratio of water to material of 61.39, producing a high polysaccharide yield (3.32 ± 0.03)%. The scavenging ability of PWBs varied on three radicals (hydroxyl > 2,2-diphenyl-1-picrylhydrazyl (DPPH) > superoxide). Furthermore, PWBs contributed to the proliferation of three probiotic bacteria (Lactobacillus acidophilus LA5, Bifidobacterium bifidum BB01, and Lactobacillus bulgaricus LB6). These investigations of PWBs provide a novel bioresource for the exploitation of antioxidant and probiotic bacterial proliferation.

Lactobacillus acidophilus was encapsulated in xanthan–chitosan (XC) and xanthan–chitosan–xanthan (XCX) polyelectrolyte complex (PEC) gels by extrusion method. The obtained capsules were characterized by X-ray diffraction and FTIR spectroscopy. The effects of microencapsulation on the changes in survival and release behavior of the Lactobacillus acidophilus during exposure to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were studied. Encapsulated Lactobacillus acidophilus exhibited a significantly higher resistance to SGF and SIF than non-encapsulated samples. In addition, the viability of free and immobilized cells of Lactobacillus acidophilus incorporated into dairy beverages was assessed for 21 days both at room temperature and in refrigerated storage. The results indicated that xanthan–chitosan–xanthan (XCX) and xanthan–chitosan (XC) significantly (p < 0.05) improved the cell survival of Lactobacillus acidophilus in yogurt during 21 days of storage at 4 and 25 °C, when compared to free cells.

Despite the widespread application of lactic acid bacterium in dairy production through its contribution to acidification, development of sensorial properties, and health-promoting effects, relatively little information is available on the cell envelope proteinases (CEPs) of Lactobacillus plantarum, especially on the proteolytic system and the production of bioactivity peptides. In this study, CEPs from a novel L. plantarum LP69 were involved in goat milk hydrolysis and generated a product with high activity that showed a degree of hydrolysis of 15.68 ± 0.74%, Angiotensin I-Converting Enzyme (ACE)-inhibitory rate of 83.25 ± 1.05%, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging rate of 64.91 ± 1.27%, and hydroxyl radical scavenging rate of 89.17 ± 1.13%. The optimized hydrolysis conditions were time of 4.5 h, temperature of 41 °C, initial pH of 8.5, and enzyme to substrate ratio (E/S) of 12% (w/w) by orthogonal experiments. Application of a stabilizer greatly promoted milk stability. A well-designed stabilizer consists of 0.05% carrageenan, 0.15% gellan gum, and 0.15% sucrose esters, which significantly raised the milk stability coefficient, R, from 70.67% to 98.57%. The storage stability of milk was evaluated during 84 days at room temperature or 4 °C. Our study depicts the contribution of CEPs from L. plantarum LP69 in goat milk, exploring a new way for the development of a functional milk product.