Food Science and Technology International

Fresh food products can be processed using UV light as a germicidal medium to reduce the food-borne microbial load. Water has been treated with UV light to obtain drinking water for quite some time. Pumpable fruit and vegetable products are generally very suitable for processing by UV light to reduce the microbial load. Today, most of these products are pasteurised to obtain microbiologically safe and nutritious products. However, pasteurisation can change the taste and flavour of such products because of the temperature and processing time. Juices from different sources can be treated by exposure to UV light at different doses. On the other hand, variables such as flow rate, exposure time, type of fruit product, juice colour and juice composition, among other variables, need to be studied to obtain fruit products with reduced microbial load, increased shelf life and adequate sensory and nutritional characteristics. Reduction of microbial load through UV light application as a disinfection medium for food products other than liquids is also being studied. Moreover, UV technology could be a source for pasteurisation of liquids, or disinfection of solid foods as an alternative technology, instead of thermal treatment or application of antimicrobial compounds.

Diacylglycerols (DAG) were synthesised by lipase-catalysed esterification of glycerol with fatty acids from palm oil deodoriser distillate (PODD). Effects of reaction parameters such as reaction time, temperature, enzyme type, enzyme load, substrate mole ratio and water content were determined. The effect of molecular sieves as a water adsorbent was also studied. Rhizomucor mieheilipase (Lipozyme RM IM) was found to be most effective among the lipases screened for DAG production. The following conditions yielded 52% (w/w) DAG: 6h reaction time, 65 °C reaction temperature, 10% (w/w) Lipozyme RM IM, 2.5:1 fatty acid to glycerol molar ratio, and 30% (w/w) molecular sieves. DAG synthesis of 10.9% (w/w) was still observed at 10% (w/w) water content.

High-purity diacylglycerol (DAG) oil was enzymatically obtained from palm oil deodoriser distillate (PODD). Free fatty acids from PODD were esterified with glycerol (2.5:1 fatty acid to glycerol molar ratio) in the presence of 10% (w/w of oil) Rhizomucor mieheilipase (Lipozyme RM IM) and 30% (w/w of oil) molecular sieves and incubated for 6h at 65 °C in a 50 mL bioreactor. After esterification, the products were deacidified by alkaline extraction and the DAG oil was further purified by silica column chromatography. After purification, up to 85.2% (w/w) of DAG was obtained. DAG profile, fatty acid composition, iodine value, slip melting point and thermal profiles were determined.

Combined processes effects of osmotic dehydration in sucrose solutions and freezing on apple cubes preservation were analysed. Two multifactorial experimental designs, in two levels, were conducted consecutively to quantify the effects of the following factors: temperature, osmotic dehydration time, concentration of the osmotic medium and freezing rate. The response variables considered were: sensory evaluation, colour, texture, water activity (aw) and reducing and total sugars. The first experimental design selected fast freezing as the best process to preserve texture and colour of the fruit. From the second experimental design, under fast freezing, were obtained the following optimal levels: 55 ºBx for the concentration of the osmotic medium, 35 ºC for the syrup temperature and 60 min for the osmotic dehydration time. A test of acceptability was performed under these conditions with 80 potential consumers on a 7-point hedonic scale, which gave 93% acceptance. Glass transition temperature (Tg') of the maximally cryoconcentrated liquid was –41.89 ºC for the product processed under optimum conditions. Significant correlations (P= 0.05) were found between sensory and instrumental responses.

Ethyl acetate and diethyl ether extracts, previously extracted with methanol, were obtained from flesh and skin of Eptatretus burgeri (hag fish) and Enedrias nebulosus (white spotted eel). Eight different extracts (4 mg/mL) were tested for DPPH free radical scavenging activity and the values were compared with commercial antioxidants (α-tocopherol and BHT). All extracts of E. burgeri exhibited significantly positive results (> 65%) in scavenging DPPH radicals compared to E. nebulosus. Thus, only E. burgeri extracts were tested for dose effect, hydrogen peroxide, hydroxyl radical, superoxide scavenging assays and heat stability at 25, 50, 75 and 100 °C for 30 min. All extracts of E. burgeri showed higher DPPH radical scavenging activities by increasing concentration. Significantly higher results were observed for hydroxyl radical scavenging activity when compared with commercial antioxidants. Relatively moderate activity and very low activity were exhibited for superoxide scavenging and hydrogen peroxide activities, respectively. Diethyl ether extracts of E. burgeri were stable with increased temperature, while ethyl acetate extracts were stable up to 75 °C. Thus, there is a high potential for E. burgeri being rich with heat-stable antioxidants that can scavenge hydroxyl radicals.

Cold storage and removal of astringency effects on quality of persimmon fruit cv. Rojo brillante were determined. Persimmon fruit were stored at 1, 8, 11 and 15 ºC (85–90% RH) and after 6, 13, 20, 27 and 34 days of storage at these temperatures, astringency was removed. Fruit quality was assessed after the removal of the astringency and after a simulated retail storage period of 6 days at 20 ºC. Storage temperature affected fruit firmness, colour, appearance, acetaldehyde and ethanol production but not total soluble solids or flavour. Fruit stored at 15 ºC followed by 6 days at 20 ºC maintained the best commercial firmness and the lowest ethanol and acetaldehyde production. Chilling injury was observed after storage at 20 ºC on those fruits previously stored at 1 or 8 ºC.

The colour, re-hydration capacity and macaroni cooking quality, related to cooked weight, cooking loss and firmness of drying of short-cut (ditalini) macaroni were evaluated. The textural properties of uncooked and cooked macaroni samples were measured using a TA-XT2i texture analyser. Protein denaturation of dried samples increased significantly with microwave power level. Physical and textural properties of macaroni samples dried with combined hot air/microwave (210 W) were equal to or better than those dried with hot air. Also, hot air/microwave combination drying exhibited superior cooking properties. Firmness of samples increased while cooking loss decreased generally with microwave application after hot air drying, i.e., hot air/microwave combination shortened the drying time and improved many of the physical, textural and cooking properties of macaroni samples.

Caco-2 cell mineral uptake assays are used to estimate the bioavailability of minerals from foods. The uptake of minerals by Caco-2 cells can be affected by several factors – particularly the conditions of the in vitro digestion process and the growth conditions of the cell culture. Therefore, a standardisation of the assays conditions is required to obtain reproducible results. This work determined the effect of enzyme demineralisation, the inactivation of the proteolytic activity of the digest and the replacement of distilled-deionised water by cell culture degree water. Treatment with Chelex-100 resin was applied to remove calcium, iron and zinc from pepsin and pancreatin-bile salts. The treatment was efficient (> 90%) for removing calcium, iron and zinc from pepsin and calcium from pancreatin-bile salts, though the efficiency was lower (= 50%) in the case of iron and zinc from pancreatin-bile salts. The use of demineralised enzymes in the digestion resulted in lower (p< 0.01) calcium and zinc contents in the soluble fraction than when non-demineralised enzymes were used. Inactivation of proteolytic enzymes at 100 ºC for 4, 10 and 15 min was tested, and it was found that 4min sufficed to maintain the integrity of the cell monolayer during the assay. The replacement of distilled-deionised water by cell culture degree water improved the viability of the cell culture.