Elizabeth A. Baldwin

Electronic Noses and Tongues: Applications for the Food and Pharmaceutical Industries

The electronic nose (e-nose) is designed to crudely mimic the mammalian nose in that most contain sensors that non-selectively interact with odor molecules to produce some sort of signal that is then sent to a computer that uses multivariate statistics to determine patterns in the data. This pattern recognition is used to determine that one sample is similar or different from another based on headspace volatiles. There are different types of e-nose sensors including organic polymers, metal oxides, quartz crystal microbalance and even gas-chromatography (GC) or combined with mass spectroscopy (MS) can be used in a non-selective manner using chemical mass or patterns from a short GC column as an e-nose or “Z” nose. The electronic tongue reacts similarly to non-volatile compounds in a liquid. This review will concentrate on applications of e-nose and e-tongue technology for edible products and pharmaceutical uses.

Use of edible coatings to preserve quality of lightly (and slightly) processed products

Lightly processed agricultural products present a special problem to the food industry and to scientists involved in postharvest and food technology research. Light or minimal processing includes cutting, slicing, coring, peeling, trimming, or sectioning of agricultural produce. These products have an active metabolism that can result in deteriorative changes, such as increased respiration and ethylene production. If not controlled, these changes can lead to rapid senescence and general deterioration of the product. In addition, the surface water activity of cut fruits and vegetables is generally quite high, inviting microbial attack, which further reduces product stability. Methods for control of these changes are numerous and can include the use of edible coatings. Also mentioned in this review are coating of nut products, and dried, dehydrated, and freeze-dried fruits. Technically, these are not considered to be minimally processed, but many of the problems and benefits of coating these products are similar to coating lightly processed products. Generally, the potential benefits of edible coatings for processed or lightly processed produce is to stabilize the product and thereby extend product shelf life. More specifically, coatings have the potential to reduce moisture loss, restrict oxygen entrance, lower respiration, retard ethylene production, seal in flavor volatiles, and carry additives that retard discoloration and microbial growth.

Improving storage life of cut apple and potato with edible coating

Abstract Use of Nature Seal™ 1020, a cellulose-based edible coating, as carrier of antioxidants, acidulants and preservatives prolonged the storage life of cut apple and potato by about 1 week when stored in overwrapped trays at 4 °C. Storage of coated apple discs in vacuum-packed trays reduced weight loss and browning compared to overwrapped tray storage. Ascorbic acid delayed browning more effectively when applied in an edible coating than in an aqueous solution. Similarly, the preservatives sodium benzoate and potassium sorbate were more effective in controlling certain microbial populations when applied in Nature Seal than in aqueous solutions, but less effective for others. Adjustment of coating pH to 2.5 gave optimal control of browning and microbial populations. Addition of soy protein to the original cellulose-based Nature Seal formulations reduced coating permeability to oxygen and water vapor. Cellulose formulations with protein were effective in controlling weight loss, especially when the pH of the formulation was raised above that of the isoelectric point, pI, of the protein.

Effect of two edible coatings with different permeability characteristics on mango (Mangifera indica L.) ripening during storage

Two types of fruit coatings were tested for their effect on external and internal mango fruit atmospheres and quality factors during simulated commercial storage at 10 or 15°C with 90‐99% RH followed by simulated marketing conditions of 20°C with 56% RH. One coating was polysaccharide-based while the other had carnauba wax as the main ingredient. These two coatings exhibited markedly different O2 permeability characteristics under laboratory conditions. This confirmed what has been reported in the literature, that polysaccharide coatings are less permeable to respiratory gases, such as O2, and more permeable to water vapor compared to carnauba wax. When applied to fruit under simulated commercial conditions, however, the difference between the coatings in permeance to respiratory gases were much reduced, most likely due to the high humidity during chilled storage. Both coatings created modified atmospheres, reduced decay, and improved appearance by imparting a subtle shine; but only the polysaccharide coating delayed ripening and increased concentrations of flavor volatiles. The carnauba wax coating significantly reduced water loss compared to uncoated and polysaccharide-coating treatments.

Formulation of zein coatings for apples (Malus domestica Borkh)

High gloss coatings are used to improve apple fruit (Malus domestica , Borkh) appearance and sales. The industry standard has been shellac-based formulations, which have problems with whitening, low gas permeability, and association with non-food uses. Zein, a natural corn protein, was used to formulate alternative, shiny coatings by dissolving zein in aqueous alcohol with propylene glycol (PG). Gloss levels on ‘Gala’ apple surfaces varied due to zein and PG content in coating formulations from that of controls to levels observed for shellac-coated fruit. At least 4% (by weight) PG was necessary for adequate gloss. However, increasing levels of both compounds resulted in increased gloss. Whitening, which occurred on the coated fruit surface upon wetting, was reduced by decreasing zein content to less than 11%. Permeability to CO2 ,O 2, and water vapor was strongly dependent on the zein content in the coating. Internal CO2 and O2 in zein-coated ‘Gala’ fruit ranged 4 � /11 and 19 � /6 kPa, respectively, by increasing zein content in the coatings. An optimum formulation with 10% zein and 10% PG was developed, applied to ‘Gala’ apple, and was found to maintain overall fruit quality comparable to a commercial shellac coating. # 2002 Published by Elsevier Science B.V.

Hydrolysis of orange peel with pectinase and cellulase enzymes

SummaryHydrolysis of polysaccharides in comminuted orange peel by commercial cellulase and pectinase enzymes has been investigated. High levels of conversion to monomeric sugars were observed after treatment with pectinase enzyme, but cellulase enzyme achieved only limited solubilization. The combination of cellulase and pectinase enzymes appears to be a most efficient system for enzymatic hydrolysis of polysaccharides in orange peel.

Aroma perception of individual volatile compounds in fresh tomatoes (Lycopersicon esculentum, Mill.) as affected by the medium of evaluation

Abstract Odor thresholds of volatile compounds in fresh tomato ( Lycopersicon esculentum Mill.) were estimated and odor units calculated to determine whether the medium of evaluation affects aroma perception. The ‘ascending method of limits’ was used to determine odor thresholds of cis -3-hexenal, hexanal, trans -2-hexenal, hexanol, cis -3-hexenol, 2-isobutylthiazole, 6-methyl-5-hepten-2-one, geranylacetone, 2-pentenal, β-ionone, 1-penten-3-one, 3-methylbutanol, 3-methylbutanal, acetone and 2-phenylethanol in deionized water, an ethanol (100 ppm)/methanol (500 ppm)/water mixture and a deodorized tomato homogenate. Cis -3-hexenal exhibited the highest level of odor units in all three media. Odor thresholds were lower in deionized water for all compounds than in the ethanol/methanol/water mixture (simulating levels found in homogenized tomato) and the thresholds were even higher in the deodorized tomato homogenate for most compounds. Distinct differences were noted in aroma descriptors for the compounds in different media. The results suggest that both qualitative and quantitative changes are occurring in the perception of volatile compounds in the different media and that ethanol and methanol alter perception of tomato aroma.

Production of ethanol from enzymatically hydrolyzed orange peel by the yeast Saccharomyces cerevisiae

We extended our previous investigations of enzymatic hydrolysis of polysaccharides in orange peel by commercial cellulase and pectinase enzymes to higher, more practical concentrations of orange peel solids. High yields of saccharification could be maintained even at substrate concentrations as high as 22–23%, but the rates of solubilization and saccharification decreased 2-3-fold. We also tested the fermentability of these hydrolysates by the yeastSaccharomyces cerevisiae, which revealed the presence of inhibitory compounds. These compounds could be removed by the filtration of hydrolyzed peel. Successful fermentations of filtered hydrolysates were achieved after pH adjustment with calcium carbonate.

Temperature of water heat treatments influences tomato fruit quality following low-temperature storage

Abstract Mature-green tomato fruit (Lycopersicon esculentum Mill. cv. Sunbeam) were treated in water for 1 h at 27 (ambient), 39, 42, 45, or 48°C, and then either ripened at 20°C (nonchilled) or stored at 2°C (chilled) for 14 days before ripening at 20°C. Treatment at 42°C reduced decay by 60%, whereas the other water temperatures were less effective. Heat treatment had no effect on time required to ripen the fruit, with 11 days required for nonchilled and 27 days required for chilled fruit (including storage time). Ripe, nonchilled tomatoes had higher respiration rates and evolved more ethylene than did chilled fruit. The 48°C treatment increased respiration and ethylene evolution compared with the other treatment temperatures. Red color development was enhanced by heat treatment, and inhibited by chilling. At red ripe, fruit were firmer as a result of storage at the chilling temperature, while heat treatment had no effect on firmness. With the exception of the 45°C treatment, chilled as well as nonchilled fruit previously treated at 39, 42, or 45°C were preferred in terms of taste and texture in informal taste tests over fruit treated at 27 or 48°C. Storage at 2°C led to an increase in electrolyte leakage, particularly in the 48°C treated fruit. Of the 15 flavor volatiles analyzed, the levels of five were decreased and two were increased with increasing temperature of heat treatment. Storage at the chilling temperature reduced the levels of five flavor volatiles. Heat treatments decreased sterols in the steryl ester fraction, several sterols in the free sterol, steryl glycoside, and acylated steryl glycoside fractions. Prestorage heat treatments, with the possible exception of the 48°C temperature, can reduce decay with only minimal adverse effects on tomato fruit quality.

Effect of Liberibacter Infection (Huanglongbing Disease) of Citrus on Orange Fruit Physiology and Fruit/Fruit Juice Quality: Chemical and Physical Analyses

More than 90% of oranges in Florida are processed, and since Huanglongbing (HLB) disease has been rumored to affect fruit flavor, chemical and physical analyses were conducted on fruit and juice from healthy (Las -) and diseased (Las +) trees on three juice processing varieties over two seasons, and in some cases several harvests. Fruit, both asymptomatic and symptomatic for the disease, were used, and fresh squeezed and processed/pasteurized juices were evaluated. Fruit and juice characteristics measured included color, size, solids, acids, sugars, aroma volatiles, ascorbic acid, secondary metabolites, pectin, pectin-demethylating enzymes, and juice cloud. Results showed that asymptomatic fruit from symptomatic trees were similar to healthy fruit for many of the quality factors measured, but that juice from asymptomatic and especially symptomatic fruits were often higher in the bitter compounds limonin and nomilin. However, values were generally below reported taste threshold levels, and only symptomatic fruit seemed likely to cause flavor problems. There was variation due to harvest date, which was often greater than that due to disease. It is likely that the detrimental flavor attributes of symptomatic fruit (which often drop off the tree) will be largely diluted in commercial juice blends that include juice from fruit of several varieties, locations, and seasons.