High pressure thermal processing of pears: Effect on endogenous enzyme activity and related quality attributes

The effect of high pressure-thermal (HPT) processing (600 MPa, 20–100 °C) on the activity of pear enzymes and related quality attributes was investigated. HPT processing at 20 °C for 5 min resulted in 32%, 74% and 51% residual activities of polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME), respectively. Increasing processing temperature to 40 and 60 °C reduced the level of PPO and POD inactivation, with the maximum residual activities of 64% and 123%, respectively observed after 3-min treatments at 40 and 60 °C. Overall, HPT at 20 to 60 °C had minimal effect on quality, although enzymatic browning was observed upon air exposure. HPT at 80 to 100 °C caused almost complete inactivation of PPO and POD with 90% and 92% inactivation respectively after 3-min processing at 100 °C, which reduced browning upon air exposure. Nevertheless, the lowest texture retention of 22% was observed under this condition.Industrial relevanceThe study examined the effects of combined high pressure thermal processing on quality related pear enzymes and related instrumental quality attributes such as colour and texture. The study enabled identification of processing regimes for enzyme inactivation and quality retention. The excellent quality retention following HPP at 20 to 40 °C makes this condition suitable for ‘fresh-like’ small portion products for immediate consumption after unpacking that do not require complete PPO and POD inactivation. On the other hand, the almost complete inactivation of oxidative enzymes PPO and POD at 100 °C makes this condition more appropriate for the production of bulk products for food service applications or pureed ingredients for baby food, or pear pieces for yoghurt, that require PPO inhibition but not necessarily high firmness retention.     

Monitoring the effects of high pressure processing and temperature on selected beef quality attributes

The combined effects of high pressure processing (HPP) and temperature on meat quality attributes were assessed in bovine M. pectoralis profundus, with particular focus on lipid oxidation and fatty acid composition. Beef samples were pressurised at 200, 300 and 400 MPa at two different temperatures 20 °C and 40 °C. Both pressure and temperature regimes had significant effects on colour, cook loss and lipid oxidation. Pressurisation at 200 MPa had a lower impact on colour parameters than higher pressurisation levels. Cook loss also increased when higher levels of pressure were applied. Across all pressure conditions, lower cook loss was observed at 40 °C compared to 20 °C. An increase in TBARS values was observed at the higher pressure levels (300, 400 MPa). While some alterations of individual fatty acids were observed, high pressure had no effect on polyunsaturated/saturated fatty acid (PUFA/SFA) or omega 6/omega 3 (n6/n3) ratio. The temperature at which HPP was applied had a significant effect on the sum of saturated (SFA), monounsaturated (MONO) and polyunsaturated (PUFA) fatty acids. HPP at 40 °C showed higher SFA and PUFA and lower MONO compared to HPP at 20 °C. These results show that high pressure at low or moderate temperatures improves the microbiological quality of the meat with minimal affects on meat quality.     

Effect of high hydrostatic pressure and thermal processing on the nutritional quality and enzyme activity of fruit smoothies

Fruit smoothie samples were thermally (P₇₀ > 10 min) or high hydrostatic pressure (HHP) processed (450 MPa/20 °C/5 min or 600 MPa/20 °C/10 min) and the total antioxidant capacity (TAC), levels of antioxidant groups [total phenols (TP), anthocyanins and ascorbic acid], instrumental colour, polyphenol oxidase (PPO) enzyme activity and dissolved oxygen were examined over a storage period of 10 h at 4 °C. Thermal processing of smoothies reduced (p < 0.001) TAC and TP values, ascorbic acid and L and a colour attributes (lightness and redness respectively) compared to fresh and HHP-450 processed samples. Conversely, it did result in complete inactivation of PPO enzyme, with no activity detected. Of the HHP treatments, HHP-450 samples had higher (p < 0.001) levels of total antioxidant, phenols and anthocyanin content than HHP-600 samples. However, the latter was more effective in reducing (p < 0.001) the endogenous enzyme activity of the smoothies. .Ascorbic acid content degraded over the storage for all smoothies. HHP-600 samples had high initial values, which declined slowly over storage, while thermal samples had the lowest initial value (0.5 h) that fell below detectable limits by 10 h. Despite these data, less pronounced effects were observed for storage. No significant effects were observed for total anthocyanin and phenolic contents as well as L and colour change (ΔE) variables. Overall, HHP processing of smoothies at moderate temperatures may be a suitable alternative to traditional thermal processing.     

High pressure processing of garlic paste: effect on the quality attributes

The effect of high pressure treatment and conventional thermal processing on the various quality attributes of garlic paste was evaluated in terms of physicochemical, enzymatic, sensory and microbiological parameters. Thermal treatment inactivated the polyphenol oxidase and peroxidase enzymes, whereas an enhanced activity was noted at 200 MPa which reduced significantly (P < 0.05) when treated with 400 and 600 MPa. Total phenolics, flavonoids and antioxidant activities showed an increasing trend with increase in pressure, whereas thermal processing was found to significantly (P < 0.05) decrease these phytocompounds. The CIE (L*, a*, b*) values were found to be better retained in high pressure‐processed pastes compared with thermally treated one. The microbial counts in terms of total plate count, yeast and mould count as well as total coliform counts were reduced significantly (P < 0.05) in both the treatments. Sensory attributes were found to be better in the case of high pressure‐processed samples as compared to the thermally treated one.     

Effect of high pressure thermal sterilization on the formation of food processing contaminants

The use of high pressure thermal sterilization (HPTS) as an emerging technology for the sterilization of foods could be a big turning point in the food industry. HPTS can result in a better overall food quality, lower thermal load applied to the product and less unwanted food processing contaminants (FPCs) as e.g. furan and monochloropropanediol/-esters.Hence, within the EU FP7 founded Prometheus-project HPTS treatments were performed for selected food systems. Therefore, two spore strains were tested, the Geobacillus stearothermophilus and the Bacillus amyloliquefaciens, in the temperature range from 90 to 121 °C at 600 MPa. The treatments were carried out in different fish system and ACES-buffer. The treatment at 90 and 105 °C showed that the G. stearothermophilus is more pressure sensitive than the B. amyloliquefaciens. The formation of FPCs was monitored during the sterilization process and compared to the amounts found in retorted samples of the same food systems. Depending on the food system the amounts of furan could be reduced between 71 and 97% for the tested temperature pressure combination even at sterilization conditions of F₀-value 7 min.Industrial relevanceThe high pressure thermal sterilization (HPTS) process is an emerging technology to produce high quality low acid food products, which are shelf-stable at ambient temperature. In addition the consumer today demands foods which are minimally processed and are healthy and safe. However, an industrial scale process has not yet been implemented.The work in this paper shows different temperature combinations (90 to 121 °C) at 600 MPa and their influence on the endospore inactivation and also on the formation of unwanted food process contaminants (FPCs), such as furan and monochloropropanediol/-esters, in comparison to retorting. The use of HPTS could lead to shorter process times and a means by which a better quality of the foods could be achieved.     

The effect of high pressure processing on nutritional value and quality attributes of Cucumis melo L.

To determine the effect of cultivar on high pressure processing (HPP) performance three commercial melon varieties were assessed before and after HPP for vitamin C and β-carotene by HPLC and for ferric ion reducing capacity (FIRC) using the Ferric Reducing Ability of Plasma (FRAP) assay. Total titrable acids (TTA), °Brix and colour were also recorded for fresh,−HPP (material cut and packaged) and +HPP samples (material cut, packaged and subject to HPP). The HP process was non-thermal so as to determine the effect of pressure alone on these phytochemicals. There were significant differences between cultivars in vitamin C, β-carotene, TTA, °Brix and colour parameters in fresh samples prior to HPP. HPP did not have an effect on TTA or °Brix, but colour was adversely affected. FIRC and vitamin C concentrations were decreased by HPP and these losses were cultivar dependent for vitamin C. Levels of β-carotene were significantly increased. Cultivar was identified as an important parameter in raw material selection for HPP and retention of vitamin C as a good measure of both quality and cultivar suitability.Industrial relevanceThere is an increasing consumer demand for fresh, natural and healthy fruit and vegetable products with an extended shelf life. This demand is driving industry to look at alternative preservation technologies. HPP has the potential to deliver safe, preserved fruit and vegetables through enzyme inactivation of microbe destruction. HPP removes the need for additives or preservatives and the process is therefore viewed as closer to “natural” by consumers. We show that HPP results in minimal loss of sensorial properties and health-promoting phytochemicals; thus providing consumers a high quality, healthy product with extended shelf life. The introduction of non-thermal processing techniques has the potential to move the focus of the Australian food processing industry from safety to the dual aims of safety and health, resulting in an increase of health-promoting phytochemicals in highly consumed processed foods.     

Effect of high pressure processing and cooking treatment on the quality of Atlantic salmon

The effect of high pressure treatment (HPP) (150 MPa and 300 MPa for 15 min) and cooking on quality of Atlantic salmon based on microbial activity, lipid oxidation, fatty acid profile, colour and texture during 6 days of storage was studied. High pressure and cooking significantly (p < 0.05) reduced microbial growth. The 300 MPa treatment and cooking showed higher L∗ and b∗ values but lower a∗ values for dark muscle compared to control and samples treated at 150 MPa. An increase in pressure resulted in an increase in hardness, gumminess and chewiness parameters, and a decrease in adhesiveness compared to control and cooked samples. Whereas cooking and 150 MPa led to similar oxidation development as control in dark muscle, the 300 MPa treatment effectively reduced the samples susceptibility to oxidation. Fatty acid profile of cooked Atlantic salmon dark muscle showed significantly (p < 0.05) lower amounts of total saturated, n−3 Polyunsaturated fatty acids (PUFA) and n−6 PUFA and significantly (p < 0.05) higher amounts of monoenes than HPP treated samples during the entire storage period. However, the most important finding of this study was that there was no significant (p > 0.05) difference between control and HPP treated samples in terms of total saturated, monoenes, n−3 PUFA and n−6 PUFA fatty acid profile. This demonstrates that HPP is a very mild process in terms of its effect on fatty acids.     

超高压处理对百香果-火龙果复合饮料品质的影响及杀菌工艺优化

以未杀菌的复合饮料作为对照组,通过设定不同低高压压力组合、保压时间、低高压时间比和协同温度,采用单因素和正交试验对百香果-火龙果复合饮料进行超高压处理,测定其菌落总数、霉菌和酵母菌、pH、可溶性固形物、稳定系数和色差△E等各项指标的变化,研究超高压处理对复合饮料品质的影响并确定最佳杀菌工艺条件。试验结果表明,经低高压压力组合200 MPa/550MPa,保压时间12min,低高压时间比1 2,协同温度30℃的超高压处理后,能有效杀灭复合饮料中的微生物,同.时对复合饮料原有品质影响较小。     

Effect of high pressure processing on the safety,shelf life and quality of raw milk

High pressure processing (HPP) was investigated as an alternative to standard raw milk processing. Different pressure levels (400–600 MPa) and exposure times (1–5 min) were tested against artificially inoculated pathogenic E. coli, Salmonella and L. monocytogenes. HPP effectively inactivated bacterial concentration by 5 log CFU/ml. The most effective HPP conditions in terms of pathogen reduction were subsequently utilised to determine the effect of pressure on microbiological shelf life, particle size and colour of milk during refrigerated storage. Results were compared to pasteurised and raw milk. HPP (600 MPa for 3 min) also significantly reduced the total viable counts, Enterobacteriaceae, lactic acid bacteria and Pseudomonas spp. in milk thus prolonging the microbiological shelf life of milk by 1 week compared to pasteurised milk. Particle size distribution curves of raw, pasteurised and HPP milk, showed that raw and HPP milk had more similar casein and fat particle sizes compared to pasteurised milk. The results of this study show the possibility of using HPP to eliminate pathogens present in milk while maintaining key quality characteristics similar to those of raw milk.     

Fermented minced pepper by high pressure processing,high pressure processing with mild temperature and thermal pasteurization

High pressure processing (HPP) and thermal pasteurization (TP) of fermented minced pepper (FMP) were comparatively evaluated by examining their impacts on microbial load, titratable acid (TA), pH, a_w, firmness, color, capsanthin, ascorbic acid (AA), and biogenic amines (BAs) after processing and during 12 weeks of storage at 25 and 37 °C. The total plate count (TPC) in FMP samples was reduced by 1.48, 0.12 and 1.58 log₁₀ CFU/g after TP (83 °C/15 min), HPP1 (500 MPa/20 °C/5 min) and HPP2 (500 MPa/50 °C/5 min), respectively. The population of spores was reduced by 1.21 log₁₀ CFU/g only after HPP2. During storage at 25 or 37 °C, the TPC in TP, HPP1, and HPP2 samples increased by 0.88/1.21, 0.41/0.62 and 0.60/0.86 log₁₀ CFU/g, respectively, while the spores decreased below the detection limit. The retention of firmness after TP, HPP1 and HPP2 was 36.91, 91.15 and 66.48% respectively, and HPP-treated samples exhibited more retention during the storage. Color of FMP samples was not changed by TP, but slightly changed by HPP1 and HPP2. The content of capsanthin retained 78.99, 93.71 and 88.19% after TP, HPP1 and HPP2, it showed a small decrease during storage. Levels of biogenic amines (BAs) in HPP2 samples were lower than that of TP and HPP1 ones. There were better sensory quality and lower microbial level in HPP-treated samples during storage, indicating that HPP is a better choice for the preservation of FMP.Industrial relevanceConsumption of fermented minced pepper (FMP), as a traditional Chinese food, is becoming increasingly popular. Considering that heat treatment may destroy some heat-sensitive quality of the products, this study evaluated the effects of high pressure processing (HPP) on quality of FMP. Findings of this study could help processors commercialize HPP to replace current thermal processing in industrial production.     

Effect of thermal and high hydrostatic pressure processing on antioxidant activity and colour of fruit smoothies

Fruit smoothie samples were thermally treated (P₇₀ ≥ 10 min) or high hydrostatic pressure (HHP) processed (450 MPa) with holding time of 1, 3 or 5 min and antioxidant activity, phenolic content and colour values (L*, a* and colour intensity) were determined. Significant reductions in antioxidant activity (p < 0.001) and phenolic content (p < 0.001) were observed at the applied pressure and a maximum treatment time of 5 min. Mean values for redness (a*) showed an increase (p < 0.001) in HHP processed smoothies compared to fresh. As expected, storage also had a significant effect on colour variables but the effect was more pronounced in high pressure treated samples stored for 30 days. Both colour and antioxidant activity were significantly affected by high pressure processing. Therefore, process optimisation of high pressure systems should be considered by processors prior to its adoption as a preservation technique in order to minimise the effect on the quality of fruit smoothie products.Industrial relevanceFruit smoothies have become popular with consumers and may significantly contribute to daily antioxidant intakes. Thermal processing has been shown to reduce the antioxidant activity of fruits, thus non-thermal methods of pasteurisation such as high hydrostatic pressure processing could help retain antioxidants in fruit smoothies offering a unique selling point for processors. The present study focussed on assessing the effect of thermal and high pressure processing on the antioxidant activity and phenolic content of fruit smoothies. Since decreases in levels of antioxidants were noted during long term storage it would appear that higher pressure treatments (> 450 MPa) might be required for better retention of antioxidant compounds in fruit smoothies.     

Effect of high pressure processing on yield,quality and storage stability of peanut paneer

Paneer was prepared from peanuts by soaking the nuts for 8 h followed by removal of skin, grinding, extraction of milk and coagulation using calcium sulphate (1% solution). In another method the peanut milk was high pressure processed at 600 MPa for 5 min before coagulation. The obtained paneer samples were vacuum packed and kept at refrigerated temperature (6 ± 1 °C) for storage and evaluated for physico‐chemical, sensory and microbial attributes. High pressure processing of milk before coagulation resulted in increase in paneer yield significantly (P < 0.05) as well as maintained the quality of the paneer to a better extent as compared to control during refrigerated storage for a period of 45 days.     

超高静压对蜂蜜主要品质的影响

为探讨超高静压(high hydrostatic pressure,HHP)对蜂蜜主要品质的影响,该研究以荔枝蜂蜜为原料,研究了不同压力(300、450、600 MPa)和保压时间(5、10、20 min)对蜂蜜中果糖和葡萄糖含量、淀粉酶和蔗糖转化酶酶活性、5-羟甲基糠醛(5-hydroxymethylfurfural,5-HMF)和二羰基化合物含量的影响。结果表明,蜂蜜中果糖和葡萄糖质量分数分别为(50.5±0.8)%和(37.1±0.9)%,果糖和葡萄糖比率(F/G)为1.35～1.39,HHP未对其含量和比值产生影响。HHP处理造成淀粉酶和蔗糖转化酶活性分别损失了17.1%～40.4%和17.2%～56.3%,压力和时间对两种酶活都具有显著性影响(P> 0.05)。蜂蜜中5-HMF含量在(1.12±0.04) mg/kg,经HHP处理后其含量有下降。3-脱氧葡萄糖醛酮是该文蜂蜜中主要的二羰基化合物,经HHP处理后其浓度显著增加22.3%～31.2%。研究结果可为HHP在蜂蜜加工中的应用提供参考。