In this study, it was investigated whether integration of microwave-heating into the pretreatment step of persimmon juice processing allows the concomitant production of both functional juice and added-value solid residue from the Diospyros Kaki “Jiro” cultivar. In this direction, persimmon pulp was treated under three different microwave-heating conditions (0.7, 4.2, and 8.4 kJ/g) prior to enzymatic maceration and compared to the non-heated material. Irrespective of microwave energy employed, the proposed hybrid treatment was highly efficient in terms of juice yield (70% w/w). The mildest heating conditions resulted in juice and residue that were both of inferior quality. Intensification of the microwave energy reduced the microbial load of the juice up to 2-log without compromising the content in total soluble solids, sugars, and L-ascorbic acid. Under the most drastic conditions, the juice was enriched in gallic acid, polyphenols, and potent DPPH^● scavengers, but its orange color faded and was more acidic. In parallel, the solid juice residue retained pro-vitamin A carotenoids (~278 µg retinol activity equivalents) and low-methoxy pectin (9 g/100 g DW). Overall, our findings can assist the efforts of the local juice processing industry to utilize persimmon fruits through energy-efficient technologies in a sustainable approach.

Virgin avocado oil (VAO), treasured for its nutritional and sensory properties, is susceptible to oxidation. To improve its oxidative stability, the feasibility of enrichment with antioxidants from avocado or olive-processing by-products via ultrasound-assisted maceration was explored. Dried, milled avocado (AL), olive leaves (OL), or olive pomace (OP) were ultrasound-macerated with laboratory-extracted VAO at 5, 10, and 20% w/w levels. Induction-period (IP) values, determined via Rancimat (110 °C, 20 L/h), increased by 1.1–1.6-fold. Maceration with AL and OL added pigments (β-carotene, lutein, α-chlorophyll, and α-pheophytin) but only AL significantly boosted α-tocopherol levels (up to 3.7-fold). Extraction of major polar phenols (chlorogenic acid, oleuropein, and hydroxytyrosol) was poor (<42 mg/kg oil). Oleanolic and maslinic acids, from OL and OP, reached up to 650 and 260 mg/kg. The IP values correlated (r = 0.796, p = 0.002) only with total polar phenol content. Maceration with OP resulted in superior antioxidant activity, extending the predicted shelf-life from 14 to 22.3 months, reaching that of a hydroxytyrosol-rich extra-virgin olive oil (24.9 months). GC-MS revealed the dominance of volatile acids in OL- and OP-VAOs, and estragole in AL-VAO highlighting some organoleptic and safety challenges to be considered, particularly when aiming to exploit these materials for the enhancement of the oxidative stability of VAOs to sustain its production.

The effect of cold smoking on the physicochemical, microbiological, and aromatic properties of Formaella-type cheese has not been previously investigated. In this study, experimental Formaella-type hard cheeses (≤38% moisture) were produced using a multistep high-temperature cooking process and subjected to weak (20 min) and intense (60 min) cold smoking, alongside an unsmoked control. Cheeses were analyzed before and after smoking and during refrigerated storage (up to 90 days). Smoking significantly influenced pH, water activity, and colour parameters, with intensively smoked cheeses exhibiting lower pH, reduced lightness (L*), and increased redness (a*) and yellowness (b*). Microbiological analyses revealed low viable counts across all samples, attributed to severe cooking steps and vacuum storage. Smoking, particularly at high intensity, significantly reduced total mesophilic counts and enterococci, while Enterobacteriaceae, staphylococci, yeasts, and moulds were not detected after manufacture. The dominant microbiota consisted mainly of lactic acid bacteria, identified by MALDI-TOF MS, including Enterococcus durans, Ent. faecium, Leuconostoc lactis, Leuconostoc mesenteroides, Streptococcus thermophilus, Lacticaseibacillus rhamnosus, and Lactobacillus curvatus. Headspace-SPME-GC-MS analysis identified 75 volatile compounds, with free fatty acids, ketones, aldehydes, and lactones as the predominant groups. Smoking introduced characteristic phenolic and furan derivatives associated with smoky aroma. Overall, smoking intensity modulated microbial dynamics and aroma development without compromising microbiological quality.