Effect of phenolic compounds on the activity of proteolytic enzymes during rennet induced coagulation of milk and ripening of miniature cheese

Olive tree leaves in dairy sheep diet: effects on rumen metabolism, microbiota composition and milk quality

Feeding ruminants with agro-industrial by-products represents an effective strategy to implement circular economy principles in animal husbandry. Olive tree leaves discarded during olive oil production are a natural source of compounds that may influence ruminant metabolism and product quality. In this study, an in vivo feeding trial evaluated the effect of dietary olive tree leaves on the rumen microbial community, animal performance and milk quality in dairy sheep. Two groups of 10 grazing Comisana ewes were supplemented with 800 g/head/d of a control pelleted concentrate (CTRL) or a concentrate containing 28% of dried olive leaves (LEAVES) for 30 days. After the adaptation period, individual milk was collected weekly and analysed for gross composition, fatty acids and renneting properties. Individual rumen liquor collected on the last day of the trial was analysed for microbial and fatty acid profiles. Moreover, the effect of olive tree leaves inclusion on dietary nutrient degradability of the LEAVES concentrate was tested in vitro. In vitro data indicated that olive leaves did not affect the rumen degradability of NDF and protein compared to CTRL. Regarding the in vivo trial, milk yield was comparable between groups, but LEAVES milk showed a greater protein percentage. Dietary olive leaves marginally affected the rumen microbiota: the Catenisphera genus was more abundant in the rumen of the LEAVES group, and Mogibacterium was found only in rumen of LEAVES ewes. The rumen liquor of LEAVES ewes showed a greater content of c9 18:1 and t6-8 18:1. Fatty acids mainly involved in biohydrogenation were found at a comparable content in the rumen of CTRL and LEAVES groups. Despite this, both dietary polyunsaturated fatty acids (c9c12 18:2 and c9c12c15 18:3) and fatty acids mainly originated from rumen biohydrogenation (trans 18:1 and 18:2 isomers) were found at a greater percentage in the LEAVES milk. Dietary olive leaves increased total monounsaturated fatty acids, polyunsaturated fatty acids, polyunsaturated fatty acids n-3 and polyunsaturated fatty acids n-6 and reduced saturated fatty acids in comparison with the CTRL diet. Among the health-promoting fatty acids, c9 18:1, c9t11 18:2, 22:5 n-6 and 22:6 n-3 were greater in the LEAVES milk. Consequently, LEAVES milk showed a lower atherogenic and thrombogenic index and a smaller hypercholesterolemic potential. Our results confirm the viability of the use of agro-industrial by-products rich in bioactive compounds in animal diets as a strategy to improve the circularity of animal production and product quality without modification to animal performance.

Effect of jujube pulp on acid- and rennet-induced coagulation properties of milk

Milk coagulation is an important step in the production of fermented dairy products such as yogurt and cheese. Jujube is gaining popularity and acceptance as a food ingredient. In China, jujube yogurt is popular among consumers. However, there is limited information on the effect of jujube on acid- and rennet-induced coagulation properties of milk. The objective of this study was to evaluate the effects of jujube pulp at different concentrations on acid- and rennet-induced coagulation kinetics of milk and the microstructure of acid- and rennet-induced gels. During acid-induced coagulation, with increasing jujube pulp concentration, the initial pH value decreased; however, the final pH value increased. The initial elasticity index (EI) value increased, and the time point at which the mean square displacement curves lost the linear trend advanced. The sample with 10% jujube pulp had the densest structure and highest EI value. During rennet-induced coagulation, with increasing jujube pulp concentration, the production rate and amount of caseinomacropeptide decreased, and the final EI value increased. Protein aggregates in rennet-induced gels became rough, and the sample with 20% jujube pulp had the highest EI value. This study provides a new perspective and understanding of the application of jujube in fermented dairy products.

Use of Tuna Visceral Pepsin in Combination with Trypsin as Digestion Aid: Enhanced Protein Hydrolysis and Bioavailability

Freeze-dried tuna pepsin powder (TPP) was prepared using maltodextrin (10%) and trehalose (5%), while trypsin-loaded beads (TLB) with 5% glycerol were obtained via chitosan/alginate ionotropic gelation. The storage stability of TPP and TLB and their proteolytic activity toward red kidney bean protein (RKB), threadfin bream surimi (TBS) and egg white protein (EWP) in varying simulated in vitro gastrointestinal (GI) tract conditions were studied. The intestinal transepithelial transportation of generated peptides was also carried out through Caco-2 cell monolayers after the cytotoxicity test. Enzyme activity was dropped when TPP and TLB in blister packs were kept for 10 weeks of storage at room (28 °C) and refrigerated (4 °C) temperatures. TPP and TLB at a level of 50% (w/w of proteins) effectively hydrolyzed RKB, TBS and EWP in a simulated in vitro GI tract, as indicated by marked protein degradation and increased degree of hydrolysis. Some peptides generated after GI digestion could transport through Caco-2 cell monolayers. Those peptides had different molecular size distribution and antioxidant activities. The highest antioxidant activity was observed for RKB hydrolysate after passing through the Caco-2 cell monolayer. Therefore, TPP and TLB from skipjack tuna viscera could potentially be used for enzyme supplementation to help digest food proteins. Food-derived bioactive peptides generated after GI digestion could assist in improving human health due to their antioxidant activity.

Progress in Extrusion-Based Food Printing Technology for Enhanced Printability and Printing Efficiency of Typical Personalized Foods: A Review

Three-dimensional printing technology enables the personalization and on-demand production of edible products of individual specifications. Four-dimensional printing technology expands the application scope of 3D printing technology, which controllably changes the quality attributes of 3D printing products over time. The concept of 5D/6D printing technology is also gradually developing in the food field. However, the functional value of food printing technology remains largely unrealized on a commercial scale due to limitations of printability and printing efficiency. This review focuses on recent developments in breaking through these barriers. The key factors and improvement methods ranging from ink properties and printer design required for successful printing of personalized foods (including easy-to-swallow foods, specially shaped foods, and foods with controlled release of functional ingredients) are identified and discussed. Novel evaluation methods for printability and printing precision are outlined. Furthermore, the design of printing equipment to increase printing efficiency is discussed along with some suggestions for cost-effective commercial printing.

Freeze-Dried Tuna Pepsin Powder Stabilized by Some Cryoprotectants: In Vitro Simulated Gastric Digestion toward Different Proteins and Its Storage Stability

The impact of maltodextrin (10%) in combination with trehalose or glycerol at different levels (2.5% and 5%) and their mixture on the stability of freeze-dried pepsin from skipjack tuna stomach was studied. Addition of 5% trehalose and 10% maltodextrin yielded the powder (TPP-T5) with highest relative pepsin activity (p < 0.05). TPP-T5 had different shapes and sizes, with mean particle size of 65.42 ± 57.60 μm, poly-dispersity index of 0.474, and zeta potential of −19.95. It had bulk density of 0.53 kg m−3 and possessed fair flowability. The wetting time for TPP-T5 was 16.36 ± 0.73 min, and solubility was 93.58%. TPP-T5 stored at room temperature under different relative humidities could maintain proteolytic activity up to 4 weeks. Commercial porcine pepsin (CP) and crude tuna pepsinogen had molecular weights of 35.2 and 43.3 kDa, respectively, when analyzed using gel filtration (Sephadex G-50) and SDS-PAGE. Tuna pepsin had comparable hydrolysis toward threadfin bream muscle protein, whey protein isolate, and kidney bean protein isolate to commercial pepsin, especially at a higher level (15 units/g protein). Digested proteins contained peptides with varying molecular weights as determined by MALDI-TOF. Therefore, pepsin from skipjack tuna stomach could replace commercial porcine pepsin and was beneficial supplement for patients with maldigestion, particularly the elderly.

Antioxidative capacity of fresh kombucha cheese fortified with sage herbal dust and its preparations

Recent studies have intensively investigated the possibility of kombucha application as non-conventional starter culture in manufacture of various fermented dairy products. Furthermore, natural extracts from medicinal and aromatic plants contain different biologically active components which often have antioxidant properties. Based on the stated above, the aim of this research was to investigate the possibility of kombucha inoculum application as a new starter culture in fresh cheese technology, as well as to investigate effects of sage (Salvia officinalis) herbal dust (by-product from filter tea factory), its essential oil and supercritical fluid extract on antioxidative activity and sensory characteristics of produced fresh kombucha cheese during 10 days of storage. In all samples, higher ABTS than DPPH radical scavenging activity was determined. Freshly prepared and 10 days stored kombucha cheeses fortified with different types of sage preparations had significantly higher FRAP values than the control sample. All analysed samples had satisfied sensory characteristics and same scores of sensory evaluation after the production. Kombucha fresh cheese with addition of different types of sage preparations can be an innovative and valuable dairy product.