5 . 2 . Bruising, trimming, and cutting
Bruising significantly affected the chemical composition of pericarp and locular tissues of tomato fruit. Vitamin C content was about 15% lower in bruised locular tissue than unbruised fruit (Moretti et al., 1998). AA retention in shred- ded iceberg lettuce is affected by the nature of the slicing method used. Higher levels of AA were retained in samples that had been prepared by manually tearing the lettuce into strips. Lettuce shredded using a sharp knife retained initially 18% less AA than the torn samples. The retention of AA in the products sliced by machine was 25–63% lower than lettuce shredded by manual tearing. Using a blunt machine blade resulted in 10% lower AA levels than when a sharp blade was used (Barry-Ryan and O’Beirne, 1999). Excessivetrimming of leafy vegetables results in loss of outer green leaves which contain more vitamins than inner leaves. Trimming of outer leaves and of the core and associated inner leaves of Chinese cabbage had a greater effect on reduction of vitamin C content than storage at 4°C for 11 days (Klieber and Franklin, 2000). Losses in vitamin C occur when vegetables are severely cut or shred- ded, as in the case of cabbage, lettuce, carrots, and other vegetables sold as salad mixes (Moza- far, 1994). Green peas and green lima beans retain their nutrients better if left in the pods than if shelled.