Measurement of volatile oxidation products from milk using solvent-assisted flavour evaporation and solid phase microextraction

A method for direct distillation of milk was developed using a high-vacuum distillation unit: solvent-assisted flavour evaporation unit (SAFE unit). Distillation of flavour compounds was carried out at low temperature, reducing the risk of artefact formation during the distillation process. After distillation, volatiles were extracted into dichloromethane and concentrated before separation on a gas chromatograph coupled with mass spectrometer detection (GCMS). Reproducibility of the SAFE method was determined by analysing the volatiles in 6 milk samples from 3 different cartons of milk. For 20 out of 27 volatile compounds, coefficients of variation below 40% were found. The method proved applicable to measure accumulation of volatile oxidation products in raw milk with 25 μm copper(II)sulfate added, and stored in the dark for 3 days at 4 °C. A simpler solid phase microextraction (SPME) method was used for the same milk, and oxidation products could only be identified after 3 days of storage at 4 °C. The SPME method can be used to describe the ongoing oxidation and the oxidative capacity of milk. Because of the high sensitivity of the SAFE method it was possible to identify compounds present in low concentrations, meaning that compounds with low-flavour thresholds and potentially high impact on the flavour may be identified.     

Contribution of coagulant and native microflora to the volatile-free fatty acid profile of an artisanal cheese

The contributions of the coagulant Cynara cardunculus and of the microflora of raw milk to the volatile-free fatty acid profile of Serra da Estrela cheese were evaluated. The experimental design included both a model system and, dual cheeses. The study in the model system showed that isovaleric acid was the predominant volatile compound after 7 d of ripening. The systems inoculated with Enterococcus faecium produced the highest amount of this volatile (ca. 135.8 mg kg⁻¹ curd), while those inoculated with Lactobacillus plantarum produced the least (21.4 mg kg⁻¹ curd); Lactococcus lactis produced moderate amounts (ca. 34.2 mg kg⁻¹ curd) but a total amount of volatile-free fatty acids similar to those found in control samples. This is considered advantageous since this volatile fatty acid confers a harsh, piquant, mature flavour to cheese, coupled with the realisation that excess volatiles may result in off-flavours. The addition of cultures in experimental cheeses helped reduce ripening time to about one half. Inclusion of Lb. plantarum led to cheeses containing the highest amounts of volatiles, and exhibiting an aroma closest to that of typical Serra da Estrela cheese.     

Equilibrium headspace analysis of volatile flavor compounds extracted from soursop (Annona muricata) using solid-phase microextraction

The influence of headspace solid-phase microextraction (HS-SPME) variables, namely, sample concentration, salt concentration and sample amount, on the equilibrium headspace analysis of the main volatile flavor compounds released from soursop was investigated. A total of 35 volatile compounds, comprising 19 esters, six alcohols, three terpenes, two acids, two aromatics, two ketones and an aldehyde, were identified. The results indicated that all response-surface models were significantly (p < 0.05) fitted for 10 target volatile flavor compounds. The results further indicated that more than 65% of the variation in the equilibrium headspace concentrations of target volatile flavor compounds could be explained by the final reduced models, with high R² values ranging from 0.658 to 0.944. Multiple optimization results showed that extraction using a 76.6% (w/w) sample concentration, 20.2% (w/w) salt and 8.2 g of blended soursop pulp was predicted to provide the highest overall equilibrium headspace concentration for the target soursop volatile flavor compounds.     

Lipid and protein oxidation of α-linolenic acid-enriched pork during refrigerated storage as influenced by diet supplementation with olive leaves (Olea europea L.) or α-tocopheryl acetate

The objective of this study was to evaluate the effect of diet supplementation with olive leaves or α-tocopheryl acetate on lipid and protein oxidation of raw and cooked n− 3 enriched-pork during refrigerated storage. Enrichment of pork with α-linolenic acid through diet supplementation with linseed oil enhanced (p ≤ 0.05) lipid oxidation in both raw and cooked chops but had no effect (p > 0.05) on protein oxidation during refrigerated storage while decreasing (p ≤ 0.05) the sensory attributes of cooked pork. Diet supplementation with olive leaves or α-tocopheryl acetate had no effect (p > 0.05) on the fatty acid composition of pork but decreased (p ≤ 0.05) lipid oxidation while exerting no effect (p > 0.05) on protein oxidation in both raw and cooked α-linolenic acid-enriched chops stored and chilled for 9 days. Moreover, olive leaves and α-tocopheryl acetate supplemented at 10 g/kg and 200 mg/kg diet, respectively, exerted (p ≤ 0.05) a beneficial effect on the sensory attributes of cooked α-linolenic acid-enriched pork chops.     

Effect of chill storage and modified atmosphere packaging (MAP) on antioxidant activity,anthocyanins, carotenoids,phenolics and sensory quality of ready-to-eat shredded orange and purple carrots

Ready-to-eat shredded orange and purple carrots, packed in air (control), or in modified atmosphere packaging [MAP; (90%N₂ + 5%O₂ + 5%CO₂ and 95%O₂ + 5%CO₂)], and stored chilled for up to 13 days, were examined for their antioxidant activity and contents of anthocyanins, carotenoids and phenolics, as well as sensory quality. Total antioxidant activity, carotenoids and phenolics of purple carrots were initially 2.8-, 2.3- and 2.9-fold higher than orange carrots, respectively. Total antioxidant activity remained relatively constant in orange carrots during storage under all treatment conditions, whereas a highly significant decrease (P<0.01) in (95%O₂ + 5%CO₂)-treated purple carrots was observed. The content of anthocyanin, only found in purple carrots, was decreased slightly during the storage period, and this was particularly significant in the 95%O₂ + 5%CO₂ treatment. In both orange and purple carrots, loss of total carotenoids occurred in the 95%O₂ + 5%CO₂ treatment. Total phenolic content of purple carrots increased at a much higher rate during storage than orange carrots. The MAP treatment (90%N₂ + 5%O₂ + 5%CO₂) gave better sensory quality and extended shelf-life for purple carrots (∼2–3 days longer shelf-life than other treatments,) but, no difference was observed for orange carrots. Shredded purple carrot can be stored under 90%N₂ + 5%CO₂ + 5%O₂ treatment for up to 10 days and high nitrogen treatment may be used in maintaining the storage quality of shredded purple carrots. Thus, purple carrots may be used in place of orange carrots to take advantage of their nutraceutical components.     

The effect of freezing compared with chilling on selected physico-chemical and sensory properties of sous vide cooked carrots

Sous vide is increasingly used to process convenience foods including ready-meals as it is reputed to give superior quality because of the mild process and the absence of oxygen in the pack. The potential for temperature abuse is greater for sous vide ready-meals than for sous vide catered items as the distribution and retailing chain for the former is usually longer. Freezing sous vide foods is, therefore, a potentially safer alternative to sous vide processed foods followed by chilling. The objective of the current study was to investigate production of sous vide frozen sliced (discs) carrots, with similar quality to sous vide chilled product. Sensory trials were used to determine the acceptable shear texture range (1.0–2.8 kN) for steamed carrots and this was the target texture in the processing trials. A Barriquand Steriflow retort was used for sous vide processing and the optimized conditions using carrot discs were: low temperature blanch (50 °C/30 min; firms product); blanch (90 °C/3 min; inactivates enzymes); sous vide cook (90 °C to core P₉₀¹⁰ values > 4 min and < 6 min); blast freeze (? 35 °C/2 h); and store (? 25 °C). Carrot discs prepared from untreated raw carrots had a firmer texture than those prepared from either blanched or blanched and frozen material. Freezing post-sous vide cooking softened texture in comparison with chilling, but freezing rate (nitrogen; blast; cabinet methods) and frozen storage (9 months) had a minimal effect on product texture and quality. Scanning electron microscopy showed no significant structural differences between sous vide frozen and chilled carrots of similar shear values. Paired comparison sensory testing of sous vide frozen and chilled sliced carrots indicated a significant preference for the latter at the 20-day storage date.Industrial relevance: The trials dealt with the effects of freezing on the quality of sous vide processed carrots. This is of relevance to companies who wish to produce texturally acceptable sous vide frozen or chilled components as part of ready-meals.     

Histamine accumulation and histamine-forming bacteria in Indian anchovy (Stolephorus indicus)

Accumulation of histamine, trimethylamine (TMA), and total volatile base nitrogen (TVB-N), as well as microbial population incidence in Indian anchovy (Stolephorus indicus) during storage in ice and at 15 and 35 °C were investigated. Histamine was as low as 1.9 mg/100 g in 15 days at ice storage, but it increased to 19.0 mg/100 g after 32 h at 15 °C. Histamine rapidly increased to 25.4 mg/100 g when stored at 35 °C for 8 h. TVB-N and TMA began to sharply increase after 11 days in ice storage, but abruptly increased after 16 and 8 h of storage at 15 and 35 °C, respectively. A high number of Enterobacteriaceae (10¹⁰–10¹¹ cfu/g) was detected and shown to be the dominant group of microbial flora during spoilage of Indian anchovy at both 15 and 35 °C. A total of 153 bacterial strains were selected from the prescreening step using various selective media. Only 75.8% of these selected isolates showed a positive reaction in Niven's differential medium, and 27.6% of the positive isolates were true histamine formers when confirmed by the enzymatic method. Prolific histamine formers were identified as Morganella morganii, Proteus vulgaris, and Enterobacter aerogenes, and produced high histamine content of 104.1–203.0 mg/100 ml. Optimum growth and histamine production of selected strains of these three species was at 35 °C in histamine evaluation broth (HEB) containing 0.5% NaCl, pH 5. E. aerogenes produced the highest histamine of 500 mg/100 ml at the optimum condition. All studied strains did not produce histamine at ⩾10% NaCl.     

Volatile compounds of modified atmosphere packaged cut iceberg lettuce: Effect of extremely low O2, season,cultivar and storage time

This study investigates the changes in volatile compounds in minimally processed iceberg lettuce as a function of season, cultivar, packaging and time. In order to achieve this, iceberg lettuce cultivars Platinas, Diamantinas and Morinas were harvested from June to September 2009. Lettuces were minimally processed and stored under three different treatments: two passive modified atmosphere packagings using films of different permeabilities, F1 (OPALEN 65 AF) and F2 (OPP/PE-L 2040 AF), and storage in air. All packages were stored at 5 °C. Gas composition and volatile compounds were assessed at 1, 5, 8 and 11 days of storage in packaged lettuce, whereas in air stored samples volatiles were analyzed only at 1 and 5 days of storage. Twenty one potent odorants were identified by GC–O. Among the months, August presented a notary increase of elemene, β-selinene and 2,3-butanedione, which likely contribute to off-odor of packaged cut lettuce. The content of O₂ and CO₂ was demonstrated to influence the formation of odorants as storage time increased. Higher amount of cis-3-hexenol was related to aerobic conditions found in the modified atmosphere packages and air stored samples after 1 day of storage, whereas levels of odorants such as 2,3-butanedione, elemene and β-selinene were significantly enhanced under anaerobic conditions after 11 days of storage. Film F2 seems to be the most promising because it kept the concentration of elemene and β-selinene lower than film F1. No clear differences were seen between the cultivars Morinas, Diamantinas and Platinas with regard to production of objectionable odorants under anaerobic conditions.     

Study of chemical changes in pasteurised orange juice during shelf-life: A fingerprinting-kinetics evaluation of the volatile fraction

The current work used fingerprinting-kinetics for the first time to monitor shelf-life changes in a low-pH, pasteurised, shelf-stable product, more particular in orange juice. Orange juice samples were stored as a function of time at four different storage temperatures (20, 28, 35 and 42 °C). To obtain insight into chemical changes in the volatile food fraction, samples were fingerprinted with headspace GC–MS. The objectives of this work were twofold: (i) to identify major chemical changes of pasteurised orange juice during shelf-life and (ii) to study the kinetics of selected shelf-life compounds in the context of accelerated shelf-life testing (ASLT). At 20 °C, changes in terpenes and a decrease in aldehydes were observed. Oxides and sulphur compounds increased and esters decreased at increased storage temperatures (at 28 °C and above). Concerning ASLT, four volatile compounds had clear temperature and time dependent kinetics within the investigated temperature range.     

Bioavailability of β-carotene isomers from raw and cooked carrots using an in vitro digestion model coupled with a human intestinal Caco-2 cell model

Not only is there limited information in the literature regarding the β-carotene (BC) isomer profile of micelles from digested foods; few studies have looked at their subsequent uptake and transport by human intestinal Caco-2 cells. Therefore, the aims of the present study were, first, to assess the profile of BC isomers in micelles from digested raw and cooked carrots; and, second, to determine their cellular uptake and transport. Greater amounts of all-trans-, 13-cis- and 15-cis-BC isomers were present in the micelles of cooked carrots compared with raw carrots. Furthermore, micelle fractions obtained from the most highly processed (pureed) carrots had greater (P < 0.05) amounts of all-trans-, 13-cis- and 15-cis-BC compared with those derived from raw and boiled carrots. A similar trend was seen with BC isomer uptake and transport. Our data suggest that the food matrix and degree of processing play important roles on carotenoid isomerization and bioavailability.     

Glycine max (L.) Merr., Vigna radiata L. and Medicago sativa L. sprouts: A natural source of bioactive compounds

The consumption of sprouts, common in Asia, has been growing in western countries, once they are a natural healthy food and considered as a valuable dietary supplement. Comparing with their mature counterparts, sprouts are usually richer in health-promoting phytochemicals. So, the nutritional composition and the biological potential of widely consumed sprouts of three species – Glycine max (L.) Merr., Vigna radiata L. and Medicago sativa L. – were compared for the first time. Phenolic compounds and phytosterols were analyzed by HPLC–DAD and organic acids by HPLC–UV. The volatile profile was determined by HS-SPME/GC–IT/MS. Fourteen phenolic compounds (including four isoflavones), three sterols one triterpene, sixteen fatty acids, seven organic acids and thirty volatile compounds were determined. The antioxidant activity was assessed against DPPH^?, superoxide and nitric oxide radicals. G. max sprouts were the most active against DPPH^? (IC₅₀ = 1.337 mg/mL), while those of M. sativa were the most effective against superoxide and nitric oxide radicals (IC₅₀ = 67 μg/mL and IC₅₀ = 426 μg/mL, respectively). Data provide evidence of great similarities between G. max and M. sativa sprouts, both being rich in phenolic compounds, fatty acids and volatiles, and exhibiting better antioxidant activity. On the other hand, V. radiata showed higher amounts of sterols, triterpenes and organic acids. In this study it was found that the sprouts are a good source of bioactive compounds in our diet with health-promoting antioxidants.     

Aroma profile of a red plum purée processed by high hydrostatic pressure and analysed by SPME–GC/MS

The volatile profile of a plum purée processed by high pressure processing (HPP) was evaluated by the method of solid-phase micro-extraction gas chromatography/mass spectrometry (SPME–GC/MS). Two pressure intensity levels and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s). Processed purées were compared to raw purée (unprocessed purée). A total of 40 volatile compounds were identified in the headspace of the plum purée. The major compounds identified were an aldehyde (hexanal) and two alcohols (hexan-1-ol and (Z)-hex-3-en-1-ol). Among the total compounds isolated (40), 23 compounds were significantly influenced by HPP. The modifications of these 23 volatiles represented changes of the 1.8% of the total aroma of the original purée. Results showed that the most intense treatments did not significantly alter the original aroma of plum purée. Therefore, HPP appears to be an alternative technology for the preservation of aromatic compounds of plum purée.Industrial relevanceHigh-pressure processing is one of the most successful technologies to obtain high-quality fruit purées. It is generally recognized that this treatment better preserves the original aroma of fruit. Two levels of pressure intensity and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s) in order to know the effect of the treatments on the original aroma of plum. The combination of pressure and holding time did not affect the original aroma of plum. Results of this paper demonstrated that high-pressure processing preserves plum puree with a fresh-like aroma. On the other hand, a study of storage would be required to assess possible changes in the stability of the plum purée taking into account other parameters such as microbiological stability and inactivation of enzymes.     

Texture preferences of 12-month-old infants and the role of early experiences

The present study examined infants’ preferences for different food textures and aimed to identify factors that play an important role in shaping these preferences. In a home setting, 70 twelve-month-old infants were exposed to cooked carrots prepared in two different textures; pureed and chopped. Infants’ mean intakes in grams for the pureed and the chopped carrots were 70.9 ± 49.1 g and 24.6 ± 28 g respectively. Infants consumed significantly more pureed carrots (t(69) = 8.50, p < 0.001) and mothers’ rating of the infants’ enjoyment for this texture was significantly higher (t(69) = 3.65, p < 0.01) than for chopped carrots. However a great variability in the consumption of chopped carrots was found within the infants. Spearman’s correlation and PLSR analysis showed that familiarity with different textures, especially chopped foods, is the strongest predictor of intake and liking of chopped carrots. Furthermore, infants with higher dietary variety, more teeth and a greater willingness to try new foods were more likely to consume more of the chopped carrots. Food pickiness and fussiness had a negative influence on the intake of, and liking for, chopped carrots. The present research is a first step to explain the variation in infants’ consumption and liking of different textures. It highlights the importance of not only varying the child’s experiences with different flavours but also with different textures to foster the infants’ transition to an adult diet.     

Volatile profile of human milk subjected to high-pressure thermal processing

High pressure thermal (HPT) treatments consist of a combination of high pressure (500–900 MPa) and temperature (70–120 °C) over a short holding time. The rapid temperature increase during compression and temperature decrease in the product upon decompression could help to reduce the hardness of thermal effects encountered in conventional thermal technologies. The objective of this study was to evaluate the effect of HPT processing (300, 600 and 900 MPa combined with 50, 65 and 80 °C) on the profile of volatile compounds in breast milk. A total of 50 volatiles, belonging to 6 different chemical groups, were detected in milk samples. In general, HPT processing increased aldehydes, ketones, furans and pyrans, as well as alcohols, however, it did not modify the levels of carboxylic acids, and reduced the content of aliphatic hydrocarbons present in the non-treated human milk samples. HPT processing enhanced the total area content of volatile compounds derived from Maillard and lipid oxidation reactions, these changes being subjected to the intensity of pressure and temperature applied. Given that the levels of volatiles were significantly modified after the application of HPT processing, we can conclude that the range of the intensity of the treatments selected was not adequate to preserve the original profile of volatile compounds in breast milk.     

Improving fruity aroma production by fungi in SSF using citric pulp

Aromas produced by microorganisms can be recognized as natural and therefore have great economic potential. Ceratocystis fimbriata has the potential to produce a variety of aromas. The aim of the present work is to increase the fruity aroma production in citric pulp (CP), a waste from the citric juice production industry, using C. fimbriata in solid-state fermentation (SSF), testing other residues as carbon (sugarcane molasses, soya molasses) and nitrogen (soya bran or urea) sources. The studies were carried out in 250 mL Erlenmeyer flasks, pH 6.0, 75% initial moisture, 30 °C, inoculum rate 1 × 10⁷ spores/g of CP, during 120 h. Total volatile compounds were quantified by headspace analysis in a gas chromatograph. The best production of volatile compounds was detected when the citric pulp was supplemented with 50% of soya bran, 25% of sugarcane molasses, and mineral saline solution. The production of total volatile reached 99.60 μmol/L g.     

Identification and quantification of phenolic acids and flavonol glycosides in Tunisian Morus species by HPLC-DAD and HPLC–MS

The total polyphenol and flavonoids in leaves of Morus alba var. alba, Morus alba var. rosa and Morus rubra were determined and identification of their components was carried out. The total content of phenolics varied between 345.20 and 631.53 mg gallic acid equivalents (GAE)/100 g dry weight (DW) basis. The total amount of flavonoids ranged between 193.87 and 398.33 mg rutin equivalents (RE)/100 g DW. Thirteen compounds were isolated by chromatography, and their structures determined to be mainly flavonol glycosides and phenolic acids. Three novel components were identified as kaempferol-7-O-glucoside, quercetin-3-O-β-glucoside-7-O-α-rhamnoside and quercetin-3-O-rhamnoside-7-O-glucoside, for the first time from mulberry leaves. Others known compounds were also identified.     

Reuterin,lactoperoxidase, lactoferrin and high hydrostatic pressure treatments on the characteristics of cooked ham

The effect of reuterin, lactoperoxidase system (LPS) and lactoferrin (LF) combined with high hydrostatic pressure (HHP) on the characteristics of sliced cooked ham during 35 days at 4 and 10 °C were investigated. Reuterin and LPS inhibited the growth of total microorganisms during 35 days at 4 and 10 °C, whereas a regrowth at 10 °C was observed when HHP was applied. Combined treatments kept total viable counts below 1.5 log cfu/g after 35 days at 10 °C. Regarding the effect of treatments on colour of cooked ham, LPS alone or in combination with HHP slightly affected L*, a* and b* values, but these changes tended to attenuate during storage. Likely, slight differences were registered in shear strength values among control and treated cooked ham. The accumulation of volatile compounds was reduced in cooked ham treated with LPS and LF in combination with HHP, even under abuse temperature conditions (10 °C).Industrial relevanceLPS applied in combination with HHP was the most effective treatment at reducing the growth of total microorganisms in refrigerated cooked ham with minor changes in its characteristics. The antimicrobial activity of such combined treatment against food-borne pathogens, which has also been reported in RTE foods, points to its usefulness to assure a safe product of sensory characteristics similar to those of untreated cooked ham.     

Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by caffeic acid and gallic acid

Caffeic acid and gallic acid were tested as inhibitors of the decrease of volatile acetate esters, ethyl esters and terpenes during storage of a white wine and a model wine medium. Wine and model wine samples were analysed by SPME along with GC–MS. At t = 0, no effect on the concentration of any volatile was observed as a result of adding each phenolic acid in any of wine or model wine samples. Many esters, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and linalool decreased during storage of Debina-white wine for up to 20 months. Caffeic acid and gallic acid at 60 mg/L inhibited the decrease of these volatiles. Isoamyl acetate, ethyl hexanoate and linalool decreased during storage of the model wine medium containing 0, 20 or 40 mg/L SO₂. Caffeic acid and gallic acid inhibited the decrease of three volatiles; SO₂ inhibited the decrease of isoamyl acetate and ethyl hexanoate. In some cases, SO₂ increased the inhibitory action of two phenolic acids. The inhibitory action of caffeic acid and gallic acid was dose dependent in the range 0–60 mg/L. Caffeic acid was active at 7.5 mg/L while gallic acid at 15 mg/L.Present results indicate that caffeic acid and gallic acid may be taken into account as potent inhibitors of the disappearance of aromatic volatile esters and terpenes in wines at concentrations similar to those existing in wines.