Application Of High Hydrostatic Pressure Treatment Research Articles

The effect of high hydrostatic pressure on the structure of whey proteins-guar gum mixture

The effect of high hydrostatic pressure (HHP) on the structural properties of whey protein concentrate (WPC) and guar gum mixture has been investigated at pH 5. WPC (6 % w/v) and guar gum (0.25 % w/v) mixture was freeze dried after adjusting pH and treated at different pressure levels (0–600 MPa) for 0–30 min. The solubility of treated powders decreased significantly (p < 0.05) as treatment time and pressure levels increased. Thermal analysis showed an increase in denaturation temperature after HHP treatment at 600 MPa. A more crystalline structure was observed in samples treated with 600 MPa for 20 and 30 min. With increasing pressure and time, particle size of the samples increased and the highest particle size was belonged to sample treated at 600 MPa for 30 min (759.66 nm). SEM results exhibited that by applying the pressure, irregularity of shapes and particle size increased while the apparent cracks decreased. FTIR results indicated that HHP treatment changed shift in bond and peak intensity. As reported in the current study, the application of HHP treatment as a green physical technology on protein-polysaccharide mixture could be used to improve interaction of protein and polysaccharide.

Effect of high hydrostatic pressure and activated film packaging on bacterial diversity of fruit puree

The aim of the present study was to determine the effect of high hydrostatic pressure (HP) and films activated with a combination of enterocin AS-48 and thymol (AF) on the microbial load and bacterial diversity of fruit puree (banana, apple, pear). HP and AF were applied singly, or in combination (AFHP). Samples were chill-stored. HP and AFHP treatments reduced viable counts significantly (P ≤ 0.05). The predominant bacterial groups in the puree were fam. Comamonadaceae (23.17%) and genera Methylobacterium (21.46%), Acidovorax (8.70%) and Sphingomonas (6.63%). Pseudomonas became relevant by the end of storage (10.50%). Most of the AF samples had higher relative abundances of Comamonadaceae, Methylobacterium, Acidovorax and Sphingomonas and lower relative abundance of Pseudomonas. Application of HP treatment markedly reduced the relative abundances of Comamonadaceae, Methylobacterium, Acidovorax and Sphingomonas. Lactobacillales increased in relative abundance upon application of HP treatment but not during storage, while Pseudomonas increased towards the end of storage. The combined treatment (AFHP) achieved greatest reduction in the relative abundances of Comamonadaceae and Methylobacterium. Results indicate that AFHP treatment had greatest effects on the bacterial diversity of the fruit puree and was also the most effective in keeping total aerobic mesophiles and Enterobacteriaceae below detectable levels.

Analysis of the microbiota of refrigerated chopped parsley after treatments with a coating containing enterocin AS-48 or by high-hydrostatic pressure

Parsley can be implicated in foodborne illness, yet chopped parsley is used as an ingredient or garnish for multiple dishes. The aim of the present study was to determine the effect of two different treatments on the bacterial diversity of parsley: (i) coating with a pectin-EDTA solution containing the circular bacteriocin enterocin AS-48, and (ii) treatment by high hydrostatic pressure (HHP) at 600MPa for 8min. Control and treated parsley were stored in trays at 5°C for 10days. Both treatments reduced viable counts by 3.7 log cycles and retarded growth of survivors during storage. The bacterial diversity of the chopped parsley was studied by high throughput sequencing (Illumina Miseq). Bacterial diversity of control samples mainly consists of Proteobacteria (96.87%) belonging to genera Pseudomonas (69.12%), Rheinheimera (8.56%) and Pantoea (6.91%) among others. During storage, the relative abundance of Bacteroidetes (mainly Flavobacterium and Sphingobacterium) increased to 26.66%. Application of the pectin-bacteriocin-EDTA coating reduced the relative abundance of Proteobacteria (63.75%) and increased that of Firmicutes (34.70%). However, the relative abundances of certain groups such as Salmonella, Shigella and Acinetobacter increased at early storage times. Late storage was characterized by an increase in the relative abundance of Proteobacteria, mainly Pseudomonas. Upon application of HHP treatment, the relative abundance of Proteobacteria was reduced (85.88%) while Actinobacteria increased (8.01%). During early storage of HHP-treated samples, the relative abundance of Firmicutes increased. Potentially-pathogenic bacteria (Shigella) only increased in relative abundance by the end of storage. Results of the present study indicate that the two treatments had different effects on the bacterial diversity of parsley. The HHP treatment provided a safer product, since no potentially-pathogenic bacteria were detected until the end of the storage period.

Microbial diversity in pitted sweet cherries (Prunus avium L.) as affected by High-Hydrostatic Pressure treatment

Sweet cherries are a highly appreciated seasonal fruit rich in anthocyanins. The purpose of the present study was to determine the effect of High-Hydrostatic Pressure (HHP) processing on the microbiological quality and bacterial biodiversity of sweet cherries. Pitted cherries inoculated with their own epiphyte microbiota to simulate a worst-case scenario of contamination during preparation and processing were treated or not by HHP (600MPa, 8min) and stored at 4°C for 60days. HHP treatment reduced total viable counts by 4.65 log cycles. The surviving bacterial fraction did not increase significantly (p<0.05) for the first 15days of storage. Concentrations of yeasts and molds were reduced below detectable levels. Upon prolonged storage (60days), microbial growth was observed. Bacterial biodiversity studied by high-throughput sequencing of the 16S rRNA gene revealed that Proteobacteria had highest relative abundance (88.70%) in the spiked cherries followed by Firmicutes (11.04%). Gluconobacter and Enterobacteriaceae together with Leuconostoc were the most abundant Operational Taxonomic Units (OTUs). Upon application of HHP treatment, 97.62% of OTUs from the surviving fraction belonged to Proteobacteria. The relative abundance of Enterobacteriaceae also decreased markedly while Acetobacteraceae (represented mainly by Gluconobacter) increased to 89.18%. Gluconobacter dominated during storage. Results from the present study provide insights on the microbiota of sweet cherries and the dynamics of the bacterial populations surviving HHP treatments that may be useful to improve the non-thermal preservation of cherries.

Comparing product stability of probiotic beverages using litchi juice treated by high hydrostatic pressure and heat as substrates

Abstract The aim of this study was to evaluate the use of litchi juice treated by high hydrostatic pressure (HHP) as substrates for producing a probiotic beverage by Lactobacillus casei . The quality attributes and product stability of fermented heat- and HHP-treated litchi juice by L. casei were compared. Compared with fermented heat-treated litchi juice, fermented HHP-treated litchi juice showed a better color, flavor and overall acceptance, and also retained more total phenolics and antioxidant capacity. Both viability counts of L. casei were more 8.0 log CFU/mL in heat- and HHP-treated litchi juice after 4 weeks of storage at 4 °C. Besides, some quality attributes in fermented heat- and HHP-treated litchi juice showed the tendency to slow decrease during storage at 4 °C, but both scores of overall acceptance of fermented heat- and HHP-treated litchi juice showed no reduction after the storage of 4 weeks at 4 °C. Overall, the application of HHP treatment could be an ideal alternative of heat treatment to ensure the microbial safety, consistent sensory and nutritional quality of fermented litchi juice prior to fermentation. Industrial relevance The study is relevant to fermentation of litchi juice by probiotic L. casei . In this study, results shown the application of high hydrostatic pressure (HHP) treatment could be an ideal alternative of heat treatment to ensure the microbial safety, consistent sensory and nutritional quality of fermented litchi juice prior to fermentation.

Effects of pressure- and thermal-pasteurization on volatiles of some berry fruits

In principle, high hydrostatic pressure (HHP) processing offers the possibility to preserve berry products while affecting their volatile components less than heat pasteurization. Therefore, we performed preliminary investigations to compare effects of HHP treatment (600 MPa, 5 min, at ambient temperature) and heat pasteurization (80 °C, 5 min) on volatile composition of raspberry, strawberry and blackcurrant purees measured by ‘electronic nose’ at 25 °C. Changes in the head space volatiles could be monitored by this method. Taking into account the confusion matrix of the discriminant analysis, heat-treatment had a more significant effect on volatile compounds than HHP. So, application of HHP treatment can retain volatiles of berry products.